Highway Engineering notes by jaspal singh sir.pdf

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TRANSPORTATION ENGINEERINGJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

CHAPTER-1 INTRODUCTION
•The process of conveyance from one point to another is termed as
“TRANSPORTATION”.
•Transportation has following effects over the socio-economic aspects of the life:
1.It helps in progress and advancement of the community.
2.Efficient transportation is essential for the economic prosperity and development
of the country.
3.It helps in movement in emergency for defense of the country and to maintain
better law and order.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

MEDIUM OF TRANSPORTATION
Transportation can be achieved by any of the following mediums:
MAJOR MEDIUM
•Land
•Water
•Air
MINOR MEDIUM
•Pipeline
•Conveyor belt
•Elevator
•Cable cars
•Ropeway
•Hyper loopJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

On the basis of the above media of transportation, following four major modes of
transportation are used:
1.Roadway/ Highway for road transportation
2.Railwayfor rail transportation
3.Waterwayfor water transportation
4.Airwaysfor air transportation
RAILWAYS
•It is the movement of multiple wagons or a train of wagons with steel wheels over
two parallel steel rails, that offer comparatively lesser resistance.
•Hence, the cost of transportation by this method is approximately one-sixth of
that by road transportation, but less flexible.
•Railways are considered as arteries of entire transportation system.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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WATERTRANSPORTATION
•It offers minimum resistance to traction, hence it is the cheapestmethod amongst the
all.
•But, the time required in this case is comparatively more.
•It is suitable for transportation of bulk goods of relatively low value.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

AIRTRANSPORTATION
•It is the fastestmethod available for transportation.
•But, the cost involved in this method is also very high.
•It is suitable for transportation of high value goods for large distance.
•This method is affected by weather conditions.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ROADWAY/ HIGHWAY
•It is the most flexible mode of transportation amongst the all.
•But, it consumes petroleum product at highest rate and rate of emission of
pollution is highest.
•Major road transportation is achieved by highways and expressways.
•Highways are special type of roads designed to allow high speed of vehicle.
•It is generally constructed on embankment as:
1.Better drainage facility
2.Safety in flood time
3.No lateral entry of public or animals
Eg-National Highways (NH) and State Highways (SH)
•Expressways are superior type of highways which are designed as a direct source
of connectivity between two defined points.
•It is also known as “freeway”. It organizes the traffic in channelized way.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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DEVELOPMENT OF ROADS
Development of roads took place in following sequential order:
ROMAN
ROADS
TRESAGUET
ROADS
TELFORD
ROADS
MACADAM
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ROMANROADS
•These were the earliest of the roads developed for their military purposes.
•The important features of these roads are:
(i)They were built straight, regardless of gradient.
(ii)The soft soil was excavated and removed uptoan extent hard strata was
reached.
(iii)The total thickness of construction was in the range of (0.75-1.2)m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

DRAWBACKS
(i)No cross-slope is provided.
(ii)No drainage system.
(iii)Large foundation stones were provided at bottom, which are of no use, as
pressure due to surface load decreases with depth. Hence, they only increases
the cost.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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TRESAGUETROADS (FRANCE)
•The main feature of these roads was reduction in overall thickness of the road,
upto30cm.
•In this case, due consideration was given to the moisture condition and drainage of
the road.
•The subgrade was prepared and a large layer of foundation stone were laid on
edges, which act as a curb stone.
•The space between the kerbis then filled with smaller stones, sizes of which are
reduced as we approach towards top.
NOTE: Metcalf road were developed in England in parallel to previous one but no
recorded literature is available for it.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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TELFORDROADS
•In these roads also, heavy/ large foundation stones were provided above the soil
subgrade and cross-slope at top surface was given to ensure removal of the water.
•A level subgrade was prepared of width 9m.
•Large foundation stones of thickness (17-22) cm was laid over the subgrade, with
larger stone at the centreand smaller at the edges to provide 1: 45 slope.
•The central portion of about 5.5cm width was filled with two layers of angular
broken stones.
•A 4cm thick gravel surfacing was laid at top and cross-drains were provided at
spacing of 90cm.
•Instead of kerbs, a layer of broken stones were used to impart lateral stability.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: From Roman roads to Telford roads, two design considerations were
common:
1.Subgrade soil was constructed on a level surface.
2.Large foundation stones were used to make bottom-most layer.
3.The major change in designing of roads was introduced by Macadam.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

MACADAM ROADS
•Macadam roads differ from previous design in following aspects:
1.Soil subgrade was also laid at a cross-slope of 1 in 36 to avoid the seepage of
water in it.
2.He was the first one to suggest that large foundation stones are not required
to be placed at the bottom layer.
3.Similarly the next layer of pavement was also constructed above this layer with
broken stones of smaller size.
4.Though the total thickness of construction was less, but load distribution was
comparatively better.
5.The size of broken stones at top was decided on the basis of stability under
animal-drawn vehicle.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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NOTE: Different types of specifications were developed for the construction of
bituminous pavement layers for use in base and surface courses.
Some of the specifications used in India are as follows:
(i)WBM (Water Bound Macadam)
(ii)PM (Penetration Macadam)
(iii)BM (Bituminous Macadam)
(iv)DBM (Dense Bituminous Macadam)
(v)WMM (Wet Mix Macadam)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which of the following is the chronological sequence in regard to road
construction/ design development?
a)Telford, Tresaguet, C.B.R., Macadam
b)Tresaguet, Telford, Macadam, C.B.R.
c)Macadam, C.B.R., Tresaguet, Telford
d)Tresaguet, Macadam, Telford, C.B.R
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DEVELOPMENT OF ROADS IN INDIA
•Government of India passed the resolution in 1927for appointment of a
Committee to examine the situation and development of roads in India under the
leadership of M.R. Jayakar.
•Major recommendations of this committee were as follows:
1.The road development in the country should be the subject of “National
Interest”.
2.An extra tax should be leaved on petrol from the users for the development of
roads and would be termed as “Central Road Fund”.
Mohen-
jo-daro
Ashoka Mughal BritishersJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

3.A semi-official technical body should be formed to give technical know-how
for development of roads.
4.A research organization should be instituted to carry out research and develop
new techniques of road development.
•As per the recommendation of JayakarCommittee, CRF (Central Road Fund)
was established in 1929.
•After the approval of government, a semi-official technical body was formed in
1934, termed as IRC (Indian Road Congress).
•In 1939, Motor Vehicle Act was brought in place to frame the laws and
ordinances relating to traffic. It governs driver vehicle and owner operation.
•A conference of Chief Engineer of all states was called by IRC for collective
development of roads in India in 1943 (1
st
20 year plan) [1943-1963] (it was
completed in 1961 only) termed as “Nagpur Road Conference”. In this, target of
16km/ 100km
2
area of country for development of roads was to be achieved.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•In 1950, Central Road Research Institute (CRRI) was established for carrying
out research of road technology.
•In 1956, National Highway Act was passed for following purposes:
(i)To declare certain selected highways as NH
(ii)To enter into any land for carrying out survey
(iii)To acquire land and take possession for development of highway
•Due to the early completion of first 20 year plan in 1961, second 20 year plan was
initiated in 1961 (1961-1981) in Bombay for development of 32km/ 100km
2
of
area.
•In 1973, HRB (Highway Research Board) of IRC was setup to give direction
and guidance for research activities in India.
•In 1978, National Transport Policy Committee (NTPC) was appointed to
prepare a comprehensive national transport policy for the country for next 10
years.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•In 1981, third 20 year road development plan was introduced (1981-2001) in
Lucknow to develop 82km/ 100km
2
of area.
•In 1988, NHAI act was passed.
•In 2000, PMGSY was launched by Indian government .
•Fourth 20 year road development plan should have been introduced in 2001, but
on the insistence of Government, IRC prepared a Road development vision 2021
and 2025.
JAYAKAR COMMITTEE (1927)
CENTRAL ROAD FUND (1929)
INDIAN ROAD CONGRESS (1934)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

MOTOR VEHICLE ACT (1939)
NAGPUR ROAD CONFERENCE (1943)
NAGPUR ROAD PLAN (1943-1963)
CENTRAL ROAD RESEARCH INSTITUTE (CRRI) (1950)
NATIONAL HIGHWAY ACT (1956) (PROPOSED)
SECOND 20-YEAR ROAD PLAN (BOMBAY ROAD PLAN)
(1961-1981)
HIGHWAY RESEARCH BOARD (1973)
NATIONAL TRANSPORT POLICY COMMITTEE (NTPC)
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THIRD 20-YEAR ROAD PLAN (LUCKNOW
ROAD PLAN) (1981-2001)
NHAI ACT PASSED (1988)
PMGSY (PRADHAN MANTRI GRAM
SADAK YOJANA) (2001)
ROAD DEVELOPMENT PLAN VISION
2021 AND 2025Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Pradhan Mantri Gram SadakYojana (PMGSY), launched in the year 2000, aims
to provide rural connectivity with all-weather roads. It is proposed to connect the
habitations in plain areas of population more than 500 persons by the year
a)2005
b)2007.
c)2010
d)2012
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Q. All the specifications for highway planning and design are given by:
a)IRC.
b)HRB
c)MVA
d)CRRI
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Q. The Road Development Plan for India for the period of 1981 to 2001 is also
known as:
a)Lucknow plan.
b)Nagpur plan
c)Bombay plan
d)Kanpur plan
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COMPARISON BETWEEN VARIOUS 20 YEAR ROAD
DEVELOPMENT PLANS
1
st
20 YEAR PLAN 2
nd
20 YEAR PLAN3
rd
20 YEAR PLAN
NAME Nagpur Bombay Lucknow
DURATION 1943-1963
(completed in 1961)
1961-1981 1981-2001
ROAD DENSITY 16 km/ 100 km
2
32 km/ 100 km
2
82 km/ 100 km
2
ROAD PATTERN Star and grid - -
EXPRESS HIGHWAY - 1600 km 20,000 km
CLASSIFICATION OF
ROADS
NH, SH, MDR, ODR
and VR
NH, SH, MDR, ODR
and VR
1.Primary roads: EH and NH
2.Secondary roads: SH and
MDR
3.Tertiary/ rural roads: VR,
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Q. Nagpur road plan is based on
a)Block pattern
b)Star and grid pattern.
c)Star and circular pattern
d)Hexagonal pattern
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LENGTH OF THE ROAD AS PER 3
rd
20 YEAR ROAD
PLAN
1. Total length of road = max (i) 4.74 ×number of towns and villages
(ii) Road density ×area
2.Length of NH =
Area(km
2
)
50
3.Length of SH = max (i)
Area(km
2
)
25
(ii) 62.5 ×number of towns and villages –length of NH
4. Length of MDH = max (i)
Area(km
2
)
12.5
(ii) 90 ×number of towns and villages
5. Length of ODR and VR = Total –(ii) –(iii) –(iv)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The length of National Highways as per 3
rd
20 year (Lucknow) road plan is given
by:
a)Area of the country/ 75
b)Area of the country/ 50.
c)Area of the country/ 40
d)Area of the country/ 25
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HIGHWAYPLANNING
•Highway planning is of great importance when the funds available are limited,
whereas the total requirement is much higher.
•The objective of highway planning are as follows:
1.To plan the overall network of road efficiently in minimum cost.
2.To divide the overall plan in phases to decide the priorities.
3.To plan for future requirement and improvement of the roads.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

CLASSIFICATIONOF ROADS
Roads are classified as follows:
A.On the basis of duration of their use:
(i)All weather roads: paved and non-paved roads
(ii)Fair weather roads: surface and non-surface roads
B. On the basis of traffic volume
C. On the basis of load transported/ tonnage
D. On the basis of location and function
1. National Highway (NH): These are main highway running through length and width of
country, connecting major ports, foreign highway, capitals of large states and large
industrial area, tourist and places of strategic importance (defense).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

2.State Highway (SH): These are arterial roads of states, connecting the national
highways of adjacent state, district headquarters and important cities.
3.Major District Roads (MDR): They are important roads within a district,
serving area of production, markets, etc.
4.Other District Roads (ODR): These are roads serving rural areas of production
and providing them outlet to the market.
5.Village Roads (VR): These are roads connecting villages.
NOTE: Urban roads are also classified as follows:
1.Arterial roads
2.Sub-arterial roads
3.Collector streets
4.Local streetsJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TYPES OF ROAD PATTERN
•The various types of road pattern may be classified as follows:
1.RECTANGULAR/ BLOCK PATTERNJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

2.HEXAGONAL PATTERN
3.RADIAL OR STAR AND BLOCK PATTERNJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

4. RADIAL OR STAR AND CIRCULAR
5. RADIAL OR STAR AND GRIDJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

MAXIMUM STAURATION SYSTEM/ UTILITY
FACTOR
•This system is used to choose the best alignment amongst the various options
available.
•It depends upon population and production.
RULES TO DECIDE THE FACTOR
1.Provide utility factor (UF) of 0.5 to the lowest population and increase it by
multiplying with 2 for next range of population. For eg-0.5, 1, 2, 4, 8, 16….
2.Provide UF of ‘1’ to the agricultural production.
3.Provide UF to industrial production as per the weightage.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ENGINEERING SURVEY FOR HIGHWAY
ALIGNMENT
•In order to decide or finalize the probable alignment, following surveys are being
carried out:
1.MAP STUDY: Various alignments are drawn on map passing through minimum
number of obstructions and maximum utilization area.
2.RECONNAISANCE: It is done by visiting the location under consideration to
identify the features which are not available on map or which are changed over
the period of time. Feasibility is also checked for the possible alignment in this
stage.
3.PRELIMINARY SURVEY: In this survey, chain, compass, levelling, soil
investigation, drainage provision, traffic studies are carried out and maximum
utilization area is decided.
4.DETAILED SURVEY: In this, planning, designing, material estimation and
cost estimation, etc. are done and a DPR is prepared.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Under the Nagpur Road Plan, which of the following are NOT relevant in
planning the road development programmein a backward district?
1.Existing agriculture drainage network of drain canals
2.Existing number of Panchayat unions
3.Existing number of villages mud-track roads
4.Number of villages with population of 10000 and above
a)1, 2, 3 and 4.
b)1, 2 and 3 only
c)1, 2 and 4 only
d)2, 3 and 4 only
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Q. In which of the following location surveys of the road soil profile, is sampling
done uptoa depth of 1m to 3m below the existing ground level?
a)Preliminary survey.
b)Final location survey
c)Construction survey
d)Material location surveyJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Preliminary project report for a road project must contain
a)The detailed estimated cost based on detailed design
b)The several alternative of the project that have been considered
c)The soil survey, traffic survey, concept design and approximate cost.
d)The contract documents for inviting tenders
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CHAPTER-2 GEOMETRIC DESIGN
Geometric design of a highway deals with all the dimensions and layout of visible
features of highway, such that it provides maximum efficiency at minimum cost and
reasonable safety.
Geometric design of highway deals with:
1.Cross-sectional elements
2.Sight distance considerations
3.Horizontal alignment details
4.Vertical alignment details
5.Intersection detailsJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

For designing of highway elements, following factors are considered:
I.DESIGN SPEED
•Design speed of vehicle depends upon type of road over which it ply (moves), for
eg–NH, SH, etc.
•Design speed of vehicle decides the cross-sectional elements like-width,
clearance, sight distance, radius of curve, superelevation, transition, gradient,
length of summit, valley, etc.
II.TOPOGRAPHY
•Topography or terrain condition influences the design speed, that in turn governs
the designing of the highway element as above.
•For eg–in plain terrain, on SH, V
per= 100 kmph whereas the same speed on
rolling terrain is, V
per= 80 kmph and on mountaneousterrain, V
per= 50 kmph.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

III.TRAFFIC FACTORS
•Traffic factors includes vehicle characteristics and human characteristics.
•In order to design highway, standard size of vehicle is considered (car) in case of
mixed traffic operation.
•Human traffic includes physical, mental and psychological characteristics of
driver and pedestrians.
IV.DESIGN HOURLY VOLUME AND CAPACITY
•The traffic volume fluctuates over the period of time, hence, the designing must be
done for peak hours, but it will be highly uneconomical to do so, hence designing
is being done for reasonable value of traffic volume, termed as “Design Hourly
Volume”.
V.ENVIRONMENTAL FACTORS
Factors like aesthetics, air pollution, noise pollution, landscaping also governs the
designing of highway elements.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

HIGHWAYELEMENTS
I.HIGHWAY CROSS -SECTION ELEMENTS
1.PAVEMENT SURFACE CHARACTERISTICS
•It depends upon pavement type, which in turn depends on availability of material,
cost, composition of traffic, climatic conditions, method of construction, etc.
•Pavement surface characteristics include:
(i)Friction
(ii)Unevenness
(iii)Reflection properties
(iv)Drainage of surface waterJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

FRICTION/SKID RESISTANCE
•It decides the operating speed and minimum distance required for stopping the
vehicle.
•It is further classifies into two:
1.Longitudinal friction
2.Lateral or transverse friction
•Maximum friction is developed when brakes are applied uptocomplete extent.
•Friction also governs rotational and translational movement of the vehicle.
•For uniform condition, Rotation = TranslationJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: (i) When the path travelled along the road surface is more than the
circumferential movement of wheels due to their rotation, it is termed as “Skid”.
Translational motion > Rotational motion
For pure skid, Rotational motion = 0
For eg-When brakes are applied, rotation stops but skidding occurs
(ii) When the circumferential movement of wheels is more than the path travelled
along the road surface, it is termed as “Slip”.
Rotational motion > Translational motion
For pure slip, translational motion = 0
For eg-When wheels of vehicle are in mud, it rotates but do not move ahead.
Condition Rotation Translation Impact
If longitudinal friction is
more
No Yes Tyreburn
If longitudinal friction is lessYes No No movement of vehicle (fuel burn)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Friction depend upon following factors:
1.Type of pavement surface (bitumen, concrete, earthwork)
2.Roughness of pavement (texture)
3.Condition of surface (dry or wet, rough or smooth)
4.Condition of tyre(new or old)
5.Speed of vehicle (high speed: less friction, low speed: more friction)
6.Extent of brake application (full or partial)
7.Temperature of tyreand pavement
NOTE: New tyreis more dependable in adverse conditionsJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•For the calculation of stopping sight distance, the longitudinal friction co-
efficient is taken to be (0.35-0.40).
•At f = 0.40, the retardation available is approximately 4m/s
2
.
•Lateral friction is taken as 0.15.
UNEVENESS
•Presence of undulations on the pavement surface is called unevenness.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•This unevenness results in:
1.Increased fatigue
2.Reduces speed
3.Increases fuel consumption
4.Increases wear and tear of vehicles
5.Increases chances of accidents
•The unevenness of pavement is measured with the help of equipment called
“Bump Indicator” (BI) in terms of unevenness index, which is the vertical
undulations of pavement surface recorded per unit length of road (in India,
mm/km is used).
•The different values of unevenness index and the corresponding serviceability of
road is as follows:
Unevenness index (mm/ km) Type of road
< 1500 Good
1500 -2500 Satisfactory
2500 -3500 Bad
> 3500 Uncomfortable Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

BUMP INDICATORJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. Internationally, the riding quality of pavement surface is quantified in
terms of roughness and is expressed as “International Roughness Index”.
2. It can also be related with unevenness index as follows:
BI (mm/km) = (IRI)
1.12
(m/km)
Unevenness of the pavement depends on following factors
1.Improper compaction
2.Use of improper compaction methods
3.Use of inferior quality materials
4.Improper surface and sub-surface drainage
5.Poor maintenance of pavement surfaceJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. ASSERTION (A): IRC has recommended a minimum coefficient of friction in
the longitudinal direction on wet pavements after allowing a suitable factor of safety
in the range 0.15 –0.30.
REASON (R): When the longitudinal coefficient of friction of 0.40 is allowed for
stopping the vehicle, the resultant retardation is 3.93 m/s
2
, which is not too
uncomfortable to the passengers.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not a correct explanation of A
c) A is true but R is false
d) A is false but R is true.
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Q. ASSERTION (A): Worn out (smooth) tyresoffer higher friction factors on dry
pavements than new tyreswith treads well intact.
REASON (R): Reduced pneumatic pressure is held in tubes which carry smooth
tyresover them
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not a correct explanation of A.
c) A is true but R is false
d) A is false but R is true
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Q. The value of lateral friction or side friction used in the design of horizontal curve
as per Indian Roads Congress guidelines is
a)0.40
b)0.35
c)0.24
d)0.15.
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Q. The longitudinal co-efficient of friction on highway for calculation of stopping
distance in geometrical design is:
a)0.3 to 0.34
b)0.5
c)0.25 to 0.29
d)0.35 to 0.4.
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Q. Which instrument is used for the measurement of the longitudinal co-efficient of
friction?
a)Bump integrator
b)Both bump integrator and roughometer.
c)Roughometer
d)Speedometer
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REFLECTIVE PROPERTIES
•Visibility over the pavement surface depends upon its color and light
characteristics, the glare caused by the reflection of head light is high on wet
pavement surface than dry pavement surface.
•Light colored pavement gives good visibility at night but produces more glare
during sunlight. On the other hand, dark color pavement offers good visibility at
day and poor at night.
2.CROSS-SLOPE/ CAMBER
•It is the slope provided to the road surface in the transverse direction to drain the
rain water from the road surface to avoid the following:
1.Stripping of bitumen from the aggregates in the presence of water.
2.Swelling and heaving of subgrade, in case water seeps into it.
3.To avoid the slipping of vehicle over the wet pavement.
4.To avoid the glare in wet pavement.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•On straight roads, it is provided by raising the centreof the carriageway w.r.t.the
edges forming the crown on the highest point along the centreline.
•On horizontal curve, with super-elevation, the drainage is provided by lifting the
outer edge.
STRAIGHT ROADS HORIZONTAL CURVE
•It is represented by any of the following ways:
1. As % : for eg-cross-slope = 5%; tan??????= 5/100
2. As fraction: for eg-cross-slope = 1 in 20 or 1/20 or 0.05; tan??????= 1/20
1 in 20 means, 1V: 20HJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The value of cross-slope depends upon following factors:
1.Type of pavement surface
2.Amount of rainfall
•Cross-slope provided would be comparatively increased if amount of rainfall is
more and pavement surface is permeable.
•The cross-slope of shoulder should be more than that of pavement, so as to avoid
accumulation of water at junction of the two.
Type of road surface Range of cross-slope
Heavy rainfallLight rainfall
Cement concrete and high type bituminous surface2% 1.7%
Thin bituminous surface 2.5% 2%
WBM and gravel pavement 3% 2.5%
Earthernroad 4% 3%Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Cross-slope of shoulder should be 0.5% more than cross-slope of adjoining
pavement, having minimum value of 3% and maximum value of 5%.
5% ≮CS
shoulder= (0.5% + CS
pavement) ≮3%
•The cross-slope on expressways for carriageway and paved shoulder and edge
strip with bituminous surface is 2.5% with rainfall exceeding 1000mm and 2% for
places having rainfall less than 1000mm.
•If too steep cross-slope is provided, then:
1.Toppling of slow moving and over-loaded vehicles.
2.Tendency of most vehicles to travel along the centreline.
3.Uncomfortable side thrust and drag on the vehicle.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TYPES OF CROSS-SLOPE
Cross-slopes are of following types:
1.Straight line Camber:
1
n
=
H
Τ
w
2
&#3627408391;=
&#3627408432;
&#3627409360;&#3627408423;
2.Parabolic Camber:
&#3627408434;=
&#3627409360;??????
&#3627409360;
&#3627408423;&#3627408432;
3.Composite Camber:
Parabolic at top and straight at sides.
NOTE: For CC pavement, straight line camber is preferred as it is easier to lay.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

3.WIDTH OF PAVEMENT/ CARRIAGEWAY
•Width of pavement depends upon width of traffic lane and number of lanes.
•The portion of carriageway width that is intended for one line of traffic movement
is termed as “traffic lane”.
•Width of traffic lane is decided on the basis of type of vehicle moving it along
with some clearance in both the sides.
•Passenger car is considered as standard vehicle to decide the width of
carriageway.
NOTE: Width of passenger car = 2.44 ≈2.5m
•For rural highway, if pavement has two or more lanes (multi-lanes), width of
single lane = 3.5m.
•The number of lanes to be provided depends upon traffic volume.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

The width of the carriageway for different conditions are as follows:
Type of road Width of carriageway
1. Single lane road 3.75 m
2. Two lane road without raised kerbs 7 m
3. Two lane road with raised kerbs 7.5 m
4. Intermediate carriageway 5.5 m
5. multi-lane pavement 3.5 m per laneJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

4.MEDIANS/ TRAFFIC SEPARATOR
•In highway with divided carriageway or pavement, a median is provided between
two sets of traffic lanes intended to divide the traffic moving in opposite
directions.
•The main function of median is to prevent head-on collision between vehicles
moving in opposite direction.
•It also serves following other functions:
1.To channelize traffic into streams.
2.To protect the pedestrians.
3.It can be used to reduce the glare of the head light of opposite moving vehicle by
providing green cover on it.
4.To segregate the slow traffic.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Medians can be provided in following forms:
1.As pavement marking
2.As physical divider (mechanical separator)
•Desirable width of median is (8-14)m.
•It includes the provision for future expansion of roads.
•In order to reduce the glare of headlight of opposite vehicle, a minimum of 6m
width is required.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•IRC recommends minimum width of 5m for median, that can be reduced to 3m
where land is restricted.
•On bridges, width required for median is in the range of (1.2-1.5)m.
•The median should be normally of uniform width throughout the length of the
pavement or carriageway, but where its width is changed atransition of 1 in 15 to
1 in 20 must be provided.
•In urban areas, minimum width of median to be provided is 1.2m and desirable
width is 1.5m
•For expressways, minimum width to be provided is 12m and desirable width is
15.5m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

5.KERB
•Kerbindicates the boundary between the pavement and median or foot path or
island or shoulder.
•Kerbsare mainly divided in following three categories:
A. Low kerb: It is of height 100mm (10cm) above the pavement surface (edge)
with a slope to enable the vehicle to climb the kerbat slow speed.
•It is also termed as “Mountable Kerb” which encourages the traffic to remain in
the through traffic lanes yet allows the driver to enter the shoulder area at slow
speed.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

B. Semi-barrier type kerb: It is provided on the periphery of the roadway where
the pedestrian traffic is high. This type of kerbis of height of about 150mm above
the pavement edge with slope of 1:1 on top 75mm.
•This kerbprevents encroachment by parking vehicles, but in case of emergency, it
is possible to drive over this kerbwith difficulty.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

C. Barrier type kerb: It is provided in built-up areas adjacent to footpaths with
considerable pedestrian traffic. Height is 20cm (200mm) above the pavement edge
of step slope of 1V: 0.25H.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

6.SHOULDER
•Shoulders are provided on both sides of the pavement, all along the road in the
case of undivided carriageway and on outer edge of divided carriageways.
•The earthernshoulder should have sufficient strength to carry the vehicular load in
case of emergency.
•The minimum shoulder width as per IRC is 2.5m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

FUNCTIONS OF SHOULDER
Shoulder serves the following functions:
1.It imparts structural stability to the pavement.
2.It increases the capacity and operating speed of pavement.
3.In emergency, it can be sued as mode of movement.
4.It can also act as a service lane for the vehicles that are disabled.
5.The surface of the shoulder may be rougher than the traffic lanes, so as to
discourage the vehicle to fly over it.
6.The color of the shoulder should be different from that of pavement, so as to
differentiate between the two.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

7.ROAD MARGINS
The various elements included in the road margins are guard rails, foot path, drive
way, cycle track, parking lane, lay-bays, front edge, road and embankment slope.
(i)Guard rail: These are provided at the edge of the shoulder when the road is
constructed running of the embankment, especially when the height of fill is
more than 3m.
(ii)Foot path/ Side walk: In order to provide safe facility to the pedestrian to walk
along the roadway, footpath/ side walk is provided in urban areas, where the
pedestrian traffic is comparatively more.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Its minimum width required is 1.5m and desirable width is 2m.
•It is provided with cross-slope of 2.5 –3% and has comparatively smoother
surface than pavement.
(iii) Drive ways: It connects the highway with local commercial establishment like
service station, fuel station, restaurant, etc.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iv) Cycle track: These are provided in urban areas for the safe movement of cycle
traffic.
•The minimum width required is 2m for cycle track and it can be increased by 1m
for each additional cycle way.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(v) Parking lanes: These are provided on urban roads to allow kerbparking.
•As far as possible, only parallel parking should be allowed as it is safer for moving
vehicles and space required would also be less.
•For parallel parking, the minimum width is 3m.
(vi) Bus bays: It may be provided by pushing back the kerbto avoid the conflict
with the moving traffic and must be located atleast75m away from intersection.
•It is used for safe loading and unloading of passengers.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vii) Lay byes: These are provided near public convenience to avoid the conflict with
running traffic. Minimum width is 3m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(viii) Frontage roads: These are provided to give access to the property along the
highway to control the access to the expressway.
(ix) Embankment slope: If pavement is constructed over embankment, slopes are
also provided along it, of magnitude 1:3.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. ROADWAY/ WIDTH OF FORMATION
It is the sum of width of pavement or carriageway including separator and the
shoulder. Roadway width is the top width of highway embankment or bottom width
of highway cutting excluding the side ways.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Width of roadway of various class of roads are as follows:
Type of roads Roadway width (m)
Plain and rolling terrainMountaineousand steep terrain
NH and SH
(a)Single lane
(b)Two lane
12
12
6.25
8.8
MDR
(a)Single lane
(b)Two lane
9
9
4.75
-
ODR
(a)Single lane
(b)Two lane
7.5
9
4.75
-
Village roads 7.5 4Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 2. ROADLAND/ LAND WIDTH/ RIGHT OF WAY
•It is the area of the road, along its alignment keeping in view its future expansion
also.
•Construction of a particular type of building is only permitted with sufficient
setback from the road boundary uptocontrol line.
•Width of land for different roads in rural areas are as follows:
Road ClassificationPlain and Rolling Mountaneous
Open Built areaOpen Built area
Expressway 90m - 60m -
NH and SH 45m 30m 24m 20m
MDR 25m 20m 18m 15m
ODR 15m 15m 15m 12m
VR 12m 10m 9m 9mJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. ASSERTION (A): Road camber helps in surface drainage.
REASON (R): In a curved road alignment, superelevation serves the purpose of
camber.
a) Both A and R are true and R is correct explanation of A
b) Both A and R are true and R is not a correct explanation of A.
c) A is true but R is false
d) A is false but R is true
[IES: 2008]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Width of carriageway for a single lane is recommended to be
a)7.5m
b)7.0m
c)3.75m.
d)5.5m
[GATE: 2000]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Cross-slope given to the pavement for safe drainage of water is:
a)Cant
b)Kerb
c)Shoulder
d)Camber.
[SSC: 2018]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The camber for hill roads in case of bituminous surface is adopted as:
a)2.0%
b)2.5%.
c)3.0%
d)3.5%
[SSC: 2011]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. A portion of the roadway contiguous with the travelled way and is intended for
accommodation of stopped vehicle is called as:
a)Carriageway width
b)Curbs
c)Shoulder.
d)Median
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Q. Right of way is the summation of the width of
a)Carriageway and shoulder
b)Carriage way, shoulder and road margins.
c)Carriage way and road margins
d)Road margins and shoulder
[SSC: 2017]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which of the following is correct statement for the cross-slope of the shoulder?
a)It is 1% flatter than the cross-slope of pavement
b)Its minimum value is 2%
c)It is 0.5% steeper than the cross-slope of the pavement.
d)Its value is equal to the cross-slope of pavement
[SSC: 2017]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The cross section for a highway is taken at
a)Right angle to the centreline
b)30m apart
c)Intermediate points having abrupt change in gradient
d)All options are correct.
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Q. Pick up the incorrect statement from the following:
The width of the right of way is decided to accommodate
a)Formation width
b)Side slopes
c)Horizontal curve
d)Vertical curve.
[SSC: 2016]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

SIGHT DISTANCE
•Sight distance is the length of the road visible ahead to the driver at any instance.
It is considered by taking the height of the eye of driver to be 1.2m and height of
object as 0.15m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Restriction to the visibility or sight distance will be caused in following cases:
1.At horizontal curve: When line of sight is obstructed by object at the inner side
of the curve.
2.At vertical curve: The LOS is obstructed by the road surface of the curve.
3.At an uncontrolled intersection: When a driver from one of the approach road is
able to sight a vehicle from another approach road towards it.
NOTE: When obstruction is not there, more sight distance is available.
•The sight distance available to the driver is dependent upon following factors:
1.Features of road, for eg-horizontal curve, traffic conditions, position of
obstruction, etc.
2.Height of driver’s eye above road surface
3.Height of object above road surfaceJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TYPES OF SIGHT DISTANCE
STOPPING SIGHT DISTANCE
SAFE OVERTAKING DISTANCE
SAFE SIGHT DISTANCE (for entering into uncontrolled intersection)
INTERMEDIATE SIGHT DISTANCE
HEADLIGHT SIGHT DISTANCEJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

STOPPING SIGHT DISTANCE
•The minimum distance visible to a driver ahead to safely stop a vehicle travelling
at design speed without collision is termed as “Stopping Sight Distance” (SSD).
•It is also termed as “Absolute Minimum Sight Distance” or “Non-Passing
Sight Distance”.
•Factors governing stopping sight distance are:
A.TOTAL REACTION TIME OF DRIVER:
•It is the time taken from the instant the object is visible to the driver to the instant
brakes are applied effectively.
•This total reaction time is further divided into different components and can be
explained as follows:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

A. PERCEPTION TIME (P)
•It is the time required for the sensation received by the eyes or ears of the driver to
be transmitted by the brain through the nervous system and spinal cord.
B. INTELLECTION TIME (I)
•It is the time required by the driver to understand the situation. It is also the time
required for comparing different thoughts, re-grouping and registering new
sensations.
C. EMOTION TIME (E)
•It is the time elapsed during emotional sensations and other mental disturbances,
fear, anger, superstition, etc, with reference to the situation to come into play. This
time varies from person to person and even for same person in different situations.
D. VOLITION TIME (V)
•It is the time taken by the driver for final action, like application of brakes.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The above can be termed as “PIEV” analysis for total reaction time.
t
R= (P+I+E+V) time
t
R, min= Reflex action time
NOTE: 1. It is also possible that the driver may apply the brake or take any other
avoiding action, like turning by the reflex action, without normal thinking process,
that is observed to be minimum time for avoiding the collision.
2. This reaction time depends upon several factors, like driver’s skill, type of
obstruction involved, environmental conditions, age, mental health, etc.
B.DESIGN SPEED:
•During the total reaction time of the driver, the distance moved by the vehicle
depends upon design speed.
•Braking distance, i.e. distance travelled by vehicle before coming to stop/ halt alos
depends on design speed.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

C.BRAKING EFFICIENCY:
•It is defined as the % of force developed by application of brakes in relation to
maximum friction available between tyreand road.
&#3627409096;
&#3627408385;=
&#3627408415;
&#3627408415;
&#3627408422;&#3627408410;&#3627408433;
×&#3627409359;&#3627409358;&#3627409358;=
&#3627408389;&#3627408424;&#3627408427;&#3627408412;&#3627408414;&#3627408413;&#3627408414;&#3627408431;&#3627408414;&#3627408421;&#3627408424;&#3627408425;&#3627408414;&#3627408413;
&#3627408396;&#3627408410;&#3627408433;&#3627408418;&#3627408422;&#3627408430;&#3627408422;&#3627408415;&#3627408424;&#3627408427;&#3627408412;&#3627408414;&#3627408410;&#3627408431;&#3627408410;&#3627408418;&#3627408421;&#3627408410;&#3627408411;&#3627408421;&#3627408414;
If η
B=100%, skid will occur on application of brakes; which is difficult to control.
Hence, braking force should not exceed the friction force between wheels and tyres.
D.FRICTIONAL RESISTANCE BETWEEN ROAD AND TYRE:
•The frictional resistance developed between the road and tyredepends upon co-
efficient of friction. Higher is co-efficient of friction, higher is the frictional
resistance and lower is SSD.
•Co-efficient of friction further depends upon condition of tyreand roads.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•It is often linked with the design speed of vehicle as follows:
E.GRADIENT:
•Gradient of the road, either in assistance or resistance of the vehicle, depends upon
type of gradient (up or down), thereby either increases or decreases SSD.
Speed (kmph) 20 –30 40 50 60 70 80 ≥100
Longitudinal friction0.4 0.38 0.37 0.36 0.36 0.350.35Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Total reaction time of a driver does not depend upon
a)Perception time
b)Brake reaction time
c)Condition of mind of the driver
d)Speed of vehicle.
[IES: 2000]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ANALYSIS OF STOPPING SIGHT DISTANCE
SSD = L
L+ L
B
The stopping sight distance of vehicle includes:
•The distance travelled by the vehicle at uniform design speed during the total
reaction time, termed as “Lag distance” (L
L).
•Distance travelled by the vehicle after the application of brake, until it stops,
termed as “Braking distance” (L
B).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

1. LAG DISTANCE &#3627408395;
&#3627408395;=&#3627408431;
&#3627408387;×&#3627408429;
&#3627408401;
Where L
L= Lag distance (m)
v
D= Design speed (m/s)
t
R= Reaction time (s)
&#3627408395;
&#3627408395;=&#3627409358;.&#3627409360;&#3627409365;&#3627409366;×&#3627408405;
&#3627408387;×&#3627408429;
&#3627408401;
Where, V
D= Design speed (kmph)
NOTE: Reaction time, t
R= 2-4 sec, but as per IRC, t
R–2.5 sec for SSD.
2. BRAKING DISTANCE
(i) For flat road:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

∆KE=Workdonebyfriction
1
2
mv
f
2
−
1
2
mv
i
2
=−FL
B
&#3627408395;
&#3627408385;=
&#3627408431;
&#3627409360;
&#3627409360;&#3627408416;&#3627408415;
(&#3627408422;)where v (m/s); g(m/s
2
)
&#3627408395;
&#3627408385;=
&#3627408405;
&#3627409360;
&#3627409360;&#3627409363;&#3627409362;&#3627408415;
(m) where V (kmph)
(ii) For gradient (ascending and descending):Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

∆KE=Workdonebyfriction
0−
1
2
mv
2
=−FL
B∓WsinθL
B
−
1
2
mv
2
=−fmgcosθL
B∓mgsinθL
B
When θis small, θ≈sinθ≈tanθ=s;cosθ=1
&#3627408395;
&#3627408385;=
&#3627408431;
&#3627409360;
&#3627409360;&#3627408416;(&#3627408415;±&#3627408428;)
where v (m/s)
&#3627408395;
&#3627408385;=
&#3627408405;
&#3627409360;
&#3627409360;&#3627409363;&#3627409362;(&#3627408415;±&#3627408428;)
where V (kmph)
+ is used for ascending gradient
-is used for descending gradient
SSD = L
L+ L
B
SSD = &#3627409358;.&#3627409360;&#3627409365;&#3627409366;×&#3627408405;
&#3627408387;×&#3627408429;
&#3627408401;+
&#3627408405;
&#3627408387;
&#3627409360;
&#3627409360;&#3627409363;&#3627409362;(&#3627408415;±&#3627408428;)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. SSD must be available at each and every section of the road.
2. As the SSD required on descending gradient is higher, it is necessary to determine
the critical value of SSD for the descending gradient on the road with gradient and
for two way traffic flow.
3. On the restricted width or on single lane road, when two-way movement of
traffic is permitted, the minimum stopping distance is equal to twice the SSD to
enable both the vehicles coming from opposite sides to stop.
4. If SSD cannot be provided on any stretch of road due to unavoidable reasons, for
the design speed available, the speed should be restricted either by installing speed
limit regulation signs or by forced reduction of speed (by speed breaker).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•This is however temporary and efforts must be made to provide SSD over the
period of time by changing the alignment or by moving the obstruction.
•IRC recommends the SSD values as follows:
Design speed (kmph) SSD (2m)
20 20
25 25
30 30
40 45
50 60
60 80
65 90
80 120
10020 180Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Consider the following factors:
1.Reaction time
2.Speed
3.Coefficient of longitudinal friction
4.Gradient
Which of these factors are taken into account for computing braking distance?
a)1 and 3
b)1, 2 and 4
c)2, 3 and 4.
d)2 and 3
[IES: 2002]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Stopping sight distance depends upon
a)Total reaction time of the driver
b)Speed of the vehicle
c)Efficiency of brakes
d)All of the given options.
[SSC: 2016]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. SSD and friction co-efficientsare
a)Directly proportional to each other
b)Unrelated
c)Inversely proportional to each other.
d)Either directly of inversely proportional; they depends upon nature
[GATE: 2002]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Stopping sight distance is the minimum distance available on a highway which is
the
a)Distance of sufficient length to stop the vehicle without collision.
b)Distance visible to a driver driving night driving
c)Height of the object above the road surface
d)Distance equal to the height of the driver’s eye above the road surface
[GATE: 2000]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The reaction time for calculating stopping sight distance may be assumed as
a)5 sec
b)2.5 sec.
c)0.5 sec
d)10 sec
[GATE: 1999]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The distance travelled by a moving vehicle during perception time and brake
reaction time is known as
a)Sight distance
b)Stopping distance
c)Lag distance.
d)Braking distance
[GATE: 1987]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OVERTAKING SIGHT DISTANCE
•If all the vehicles ply on a road at the design speed, then there would be no need
for overtaking, but practically this never happens.
•Hence, vehicle moving at design speed needs to overtake slow moving vehicle.
•The minimum distance open to the vision of the driver of a vehicle intending to
overtake slow vehicle with safety against traffic in opposite direction is termed as
“OSD” or “Safe Passing Sight Distance” or “Safe Passing Sight Distance”.
•OSD is measured along centreline of the road, considering eye level of the driver
at 1.2m above the surface, observing the object at height of 1.2m.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

FACTORSAFFECTING OSD
1.Speed of vehicle
a)Overtaking vehicle
b)Overtaken vehicle
c)Vehicle coming from opposite direction
2.Reaction time and skill of the driver
3.Gradient of road
4.Condition of overtaking vehicle, which governs the rate of acceleration
5.Distance between two vehicles (overtaking and overtaken)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ANALYSISOF OSD
A = Overtaking vehicle
B = Overtaken vehicle
V = Design speedJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

a)d
1= It is the distance travelled by overtaking vehicle “A” during the reaction
time “t
r” of the driver, before starting to overtake vehicle “B” at speed of V
B.
b)d
2= It is the distance travelled by vehicle “A” during the actual overtaking
operation of time “T”.
c)d
3= It is the distance travelled by on coming vehicle “C” during the actual
overtaking operation of “A” for time “T”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ASSUMPTIONS IN ANALYSIS OF OSD
1.Overtaking vehicle is forced to reduce its speed uptothe speed of overtaken
vehicle for reaction time.
2.When the driver of vehicle finds sufficient clear gap, decides within the reaction
time to overtake.
3.The vehicle ‘A’ accelerates and overtakes the vehicle ‘B’ within a distance ‘d
2’
during the time ‘T’.
4.The distance ‘d
2’ can be splittedinto three components.
5.During this overtaking time, the vehicle ‘C’ coming from opposite direction
travels through distance ‘d
3’.
d
1= v
b×t
r
d
1= 0.278 V
b×t
r(where V
bis in kmph)
NOTE: t
r= 2 secJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

d
2= 2s + b
Where s = space headway = minimum spacing between two vehicles which depends
upon the speed of the vehicle
s = (0.7 v
b+ 6) (where v
bis in m/s)
s = (0.2 V
b+ 6) (where V
bis in kmph)
B = v
b×T = 0.278 V
b×T
d
2= v
b×T +
1
2
a T
2
d
2= 0.278 V
b×T +
&#3627409359;
&#3627409360;
a T
2
2s + b = 0.278 V
b×T +
1
2
a T
2
&#3627408403;=
&#3627409362;&#3627408428;
&#3627408410;
Where, a = acceleration of overtaking vehicle (m/s
2
)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: Overtaking time ‘T’ depends upon its average acceleration and speed of
overtaken vehicle
d
3= v
d×T = 0.278 V
d×T
Where, V
d= design speed (kmph)
OSD = d
1+ d
2+ d
3
OSD = (0.278 V
b×t
r) + (0.278 V
b×T +
&#3627409359;
&#3627409360;
a T
2
) + (0.278 V
d×T)
NOTE: In case the speed of overtaken vehicle is not given, it may be taken as 4.5
m/s or 16 kmph less than design speed.
v
b(m/s) = v
d(m/s) –4.5 m/s
V
b(kmph) = V
d(kmph) –16 kmph Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

The acceleration of the overtaking vehicle varies depending upon the several
factors:
1.Type of vehicle
2.Condition of vehicle
3.Load on the vehicle
4.Speed of vehicle
5.Characteristics of driver
Maximum overtaking acceleration at different speeds are as follows:
Speed (kmph) Acceleration (m/s
2
)
25 1.41
30 1.30
40 1.24
50 1.11
65 0.92
80 0.72
100 0.53Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

EFFECT OF GRADIENT ON OSD
•The overtaking sight distance requirement may increase on ascending as well as
descending gradient.
•In descending gradient, acceleration of overtaking vehicle increases, but overtaken
vehicle may also accelerate to a greater distance ‘b’ during the overtaking time.
Thus, we cannot comment as there are two variables.
•In ascending gradient, the acceleration of overtaking vehicle will be less but
overtaken vehicle would also move with lower velocity, hence we cannot
comment on OSD.
•Hence, on mild gradient (as that in plain and rolling terrain), OSD at both
ascending and descending gradient are generally equal to that of level stretch.
•However, for steeper grades, OSD should be greater than minimum OSD at plain
level road.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OSD on two-lane highway for different speeds are as follows:
Speed (kmph) OSD (m)
40 165
50 275
60 300
65 340
80 470
100 640Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: . It is desirable that OSD should be available on most of the road stretches.
•On road stretches with two-way traffic:
OSD = d
1+ d
2+ d
3
•On road stretches with one-way traffic
OSD = d
1+ d
2Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OVERTAKING ZONE
•If OSD cannot be provided over a particular stretch of a road section, in such
cases, for same overtaking of the vehicle at design speed, opportunity must be
given to the vehicle. Such zones are termed as “Overtaking Zones”.
SP
1= Sign post “Overtaking zone ahead”
SP
2= Sign post “End of Overtaking zone”Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. If at stretches of road, OSD cannot be provided as suggested by IRC, in
such case, sight distance is desirable to be kept as twice of SSD and it is termed as
“Intermediate Sight Distance” (ISD).
ISD = 2×SSD
2. The measurement of ISD can be made assuming both the height of eye of driver
and that of object to be 1.2m.
OSD > ISD > SSD
Distance (m) Reaction time (s) Height (m)
Driver’s eye Object
SSD 2.5 1.2 0.15
OSD 2 1.2 1.2
ISD 2.5 1.2 1.2
Space headway 0.7 - -Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. At highway stretches where the required overtaking sight distance cannot be
provided, it is necessary to incorporate in such sections the following:
a)At least twice the stopping sight distance.
b)Half of the required overtaking sight distance
c)One-third of the required overtaking sight distance
d)Three times the stopping sight distance
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SIGHT DISTANCE AT INTERSECTION
A.UNCONTROLLED INTERSECTION
•On all approaches of intersecting roads, there should be clear view across the
corner from the sufficient distance so as to avoid the collision.
•The design sight distance at intersection may be based on three possible
conditions:
1.Enabling the approaching vehicle to change the speed (slow down).
2.Enabling the approaching vehicle to stop.
3.Enabling stopped vehicle to cross the road.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

1.The sight distance should be sufficient to enable either one or both approaching
vehicle to change the speed to avoid collision.
•The vehicle approaching from the minor must slow down.
•Total reaction time required for the driver to decide to change speed is 2s and
at-least one more second is required for making the change in speed.
Total time = 2 + 1 = 3 sec
Hence, SD = 0.278 V
d×t
r= (0.278 V
d×3 ) mJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

2.The distance for the approaching vehicle should be sufficient to bring either both
or one of the vehicle before reaching the conflict. Hence, it will be equal to SSD.
3.In this case, vehicle entering the intersection from the minor roads are controlled
by ‘STOP’ or ‘GIVE WAY’ sign. So, the vehicles have to stop and then proceed
to cross the main road.
•In this case, the total time required by the stopped vehicle would include to start,
accelerate and cross the main road before another vehicle travelling at design
speed approaches it from main road.
NOTE: For safety consideration, the sight distance at uncontrolled intersection is
maximum of above three cases.
B.CONTROLLED INTERSECTION
•At signalized intersection, the above three requirements are not applicable.
•At rotary intersection, the sight distance should be atleastequal to SSD, for design
speed of rotary.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The sight distance available on a road to a driver at any instance depends on
1.Features of the road ahead
2.Height of the driver’s eye above the road surface
3.Height of the object above the road surface
a)1 and 2 only
b)1 and 3 only
c)2 and 3 only
d)1, 2 and 3.
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HORIZONTAL ALIGNMENT OF HIGHWAY
•Change in direction is required in highway alignment due to the various reasons:
1.Topographic conditions
2.Obligatory points
•Various design elements to be considered in the horizontal alignment are:
1.Design speed
2.Radius of curve
3.Type and length of transition curve
4.Width of pavement
5.Superelevation
6.Set-back distanceJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

DESIGNSPEED
•The design speed is the main factor on which most of the geometric design
elements depends including horizontal alignment.
•The design speed of road depends upon class of road and terrain.
•Classification of terrain and design speed for different class of road are as follows:
Terrain Classification Cross slope (%)
Plain 0 –10
Rolling 10 –25
Mountaneous 25 –60
Steep Above 60Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Design speeds are also being defined for urban roads.
•Two values of the speed i.e. ruling and minimum are being specified for each type of road.
•As far as possible, an attempt should be made to design all the geometric elements for
ruling speed. However, if site conditions and economic considerations doesn’t permits so,
designing must be done for minimum design speed.
Type of road Design speed (kmph)
Plain Rolling Mountaneous Steep
Ruling Minimum Ruling Minimum Ruling Minimum Ruling Minimum
Expressway 120 100 100 80 80 60 40 60
NH and SH 100 80 80 65 50 40 40 30
MDR 80 65 65 50 40 30 30 20
ODR 65 50 50 40 30 25 35 20
VR 50 40 40 35 25 20 25 20Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

HORIZONTAL CURVE
•It is a curve, in plan to provide change in direction to centreline of the road.
•It may be different in terms of:
a)Radius of the curve (m)
b)Degree of the curve: It is the central angle subtended by an arc of length 30m.
2πR
360
o
=
30
D°
D°=
180°
πR
×30=
1720
??????
??????=
&#3627409359;&#3627409365;&#3627409360;&#3627409358;
??????°Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•When a vehicle travels on horizontal curve, the centrifugal force acts horizontally
outwards through the CG of the vehicle.
•This centrifugal force depends upon speed of vehicle on a radius of horizontal
curve.
•It will be counteracted by lateral/ transverse
friction developed between the tyreand
pavement which helps the vehicle to change
direction along the curve.
P
c=
mv
2
R
=
Wv
2
gR
Here,
??????&#3627408412;
&#3627408406;
=
&#3627408431;
&#3627409360;
&#3627408416;&#3627408401;
istermedas“Impact factor”
or “Centrifugal Ratio”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The force acting on vehicle has the tendency to either overturn the vehicle
outwards about wheels and to skid the vehicle laterally outwards.
For stability of vehicles, both the conditions are to be checked as follows:
A.OVERTURNING EFFECT
For no overturning, M
R≥M
o
M
R= W×
b
2
≥P
c×h
Where, b = c/c distance of tyreJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

??????&#3627408412;
&#3627408406;
=&#3627408392;.&#3627408389;.≤
&#3627408411;
&#3627409360;&#3627408417;
(Condition to prevent overturning)
If I.F. =
b
2h
: Vehicle is on verge of overturning
If I.F. >
b
2h
: Vehicle will overturn
B.TRANSVERSE SKIDDING EFFECT
For no skidding, F
A+ F
B≥P
C
μ(R
A+R
B)≥P
c
μW≥P
c
P
c
W
≤μorf
I.F. ≤??????&#3627408424;&#3627408427;&#3627408415;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. If pavement is kept horizontal across the alignment, the pressure on the
outer wheel will be higher due to P
cacting outwards.
2. When the limiting condition for overturning occurs, the pressure on the inner
wheels becomes zero.
3. Since pressure on outer wheel is comparatively more, it damages the pavement by
the development of ruts over it.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Hence, to avoid both overturning and sliding,
??????&#3627408412;
&#3627408406;
≤min (i)
&#3627408411;
&#3627409360;&#3627408417;
(ii) f
The relative danger of lateral skidding and overturning depends upon whether ‘f’ is
lower or higher than
b
2h
.
If f <
b
2h
: Transverse skidding before overturning
If f >
b
2h
: Overturning before transverse skiddingJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

SUPERELEVATION
•In order to counteract the effect of centrifugal force, and to reduce the tendency of
the vehicle to overturn and skid, outer edge of pavement is raised w.r.t.inner
edges, thus providing a transverse slope throughout the length of the horizontal
curve.
•This transverse inclination to the pavement surface is known as “Superelevation/
Cant/ Banking”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

E = Total superelevation height of outer edge
E = eB
ANALYSIS OF SUPERELEVATION
Forces acting on vehicles are:
1.Self-weight (W) (vertically downward)
2.Centrifugal force (P
c) (acting horizontally in outward direction)
3.Frictional force (F) (Laterally inward along the pavement surface)
For equilibrium condition, σF
x=0
Wsinθ+F
1+F
2=P
ccosθ……(i)
෍F
y=0
R
1+R
2=Wcosθ+P
csinθ…..(ii)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

From (i) and (ii), P
ccosθ−fsinθ=Wsinθ+fcosθ
P
c
W
=
sinθ+fcosθ
cosθ−fsinθ
When θis small, sinθ≈tanθ,cosθ≈1
&#3627408392;&#3627408422;&#3627408425;&#3627408410;&#3627408412;&#3627408429;&#3627408415;&#3627408410;&#3627408412;&#3627408429;&#3627408424;&#3627408427;=&#3627408386;&#3627408414;&#3627408423;&#3627408429;&#3627408427;&#3627408418;&#3627408415;&#3627408430;&#3627408416;&#3627408410;&#3627408421;&#3627408427;&#3627408410;&#3627408429;&#3627408418;&#3627408424;=
??????
&#3627408412;
&#3627408406;
=
&#3627408429;&#3627408410;&#3627408423;&#3627409097;+&#3627408415;
&#3627409359;−&#3627408415;&#3627408429;&#3627408410;&#3627408423;&#3627409097;
=
&#3627408414;+&#3627408415;
&#3627409359;−&#3627408414;&#3627408415;
1-ef ≈1
??????
&#3627408412;
&#3627408406;
=&#3627408414;+&#3627408415;=
&#3627408431;
&#3627409360;
&#3627408416;&#3627408401;
&#3627408432;&#3627408417;&#3627408414;&#3627408427;&#3627408414;&#3627408431;&#3627408418;&#3627408423;
&#3627408422;
&#3627408428;
&#3627408414;+&#3627408415;=
&#3627408405;
&#3627409360;
&#3627409359;&#3627409360;&#3627409365;&#3627408401;
&#3627408432;&#3627408417;&#3627408414;&#3627408427;&#3627408414;&#3627408405;&#3627408418;&#3627408423;
&#3627408420;&#3627408422;
&#3627408417;&#3627408427;
R = Radius of curve (m)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 1. It may be seen that the contribution of superelevation ‘e’ (0.07) is much
less than that of lateral friction ‘f’ (0.15) in counteracting centrifugal force.
2. In some situations, eg-at intersection or some obstruction, it is not possible to
provide superelevation, in such cases, friction counteracts the centrifugal force and
if friction is also not sufficient, then radius of curve is increased which if not
possible, speed of vehicle negotiating a turn must be reduced to following: Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

e + f =
??????
2
127&#3627408453;
When e = 0, ??????
??????=127????????????
Where, V
a= allowable speed
3. In some cases, superelevation may be negative, in such cases,
f –e =
??????
2
127&#3627408453;
4. e = f (V, R, f)
Hence, the value of e needed increases with increase in speed and with decrease in
radius of curve.
Hence, ‘e’ cannot be increased beyond a particular limit, as it would lead to the
toppling/ instability of slow moving vehicles with high CG, eg-bullock carts, truck,
lorry, etc.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Value of e
maxfor different terrain are as follows:
•From drainage consideration, it is necessary to have minimum cross-slope to
drain out surface water.
•If e
calculated< cross-slope of road, then cross-slope may be provided as
superelevation only, by eliminating the crown and negative superelevation on
outer edge.
•In very flat curve with large value of P
c, and negative superelevation may be
permitted on outer edge.
Terrain type e
max(%)
1. Plain and rolling 7
2. Mountaneousand steep: not bounded by snow10
3. urban/ built-up area 4Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•As per IRC, radius of the curve beyond which ‘e’ is not required is as follows:
Design speed
(kmph)
Radius of horizontal curve (m)
4% 3% 2.5% 2% 1.7% (Camber)
20 50 60 70 90 100
25 70 90 110 140 150
30 100 130 160 200 240
35 140 180 220 270 320
40 180 240 280 350 420
50 280 370 450 550 650
60 470 620 750 950 1100Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

DESIGN OF SUPERELEVATION
•Since, mixed traffic operates on our road, the superelevation design is very
complex.
•Providing a lower value of superelevation and relying on lateral friction would be
unsafe for fast moving vehicles and providing higher value of superelevation
creates problem for slow moving vehicles.
•Hence, a compromised value for ‘e’ is designed as follows:
Step-1: The superelevation is calculated for 75% of design speed, neglecting the
lateral friction
f = 0; V
design= 0.75V
e=
(0.75V)
2
127R
=
V
2
225RJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Step-2: If the calculated value of e is less than 7%, so obtained ‘e’ is provided.
If value of ‘e’ obtained is more than 7%, then provide e = 7% and check for lateral
friction only (plain and rolling).
Step-3: Check for friction developed for maximum value of e = 7% at full value of
design speed.
f=
V
2
127R
−0.07
If the value of ‘f’ calculated is less than 0.15, the superelevation of 7% is safe for
design but if it comes out to be more than 0.15, then the speed of vehicle has to be
restricted to safe value, which is less than design speed.
Step-4: The allowable speed at the corner is computed as follows:
e + f =
V
2
127R
0.07 + 0.15 =
V
a
2
127RJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

&#3627408405;
&#3627408410;=&#3627409363;.&#3627409360;&#3627409366;&#3627408401;
Where, V
ais in kmph and R is in m.
•If the allowable speed is higher than the design speed, then the design is adequate
but if it is less than design speed, the speed is limited to the allowable speed.
•Speed can be reduced by warning sign or by speed limit regulation signs.
•On important highways, speed is not reduced, hence, the curve should be re-
aligned with larger radius of curvature.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ATTAINMENT OF SUPERELEVATION IN THE FIELD
•Introduction of superelevation on horizontal curve in the field is very typical as on
straight portion of road cross-section, normal camber is provided with crown at
the centre, sloping downwards on both the sides.
•But the portion of cross-section on circular curve is superelevated uniformly
sloping down from outer edge uptothe inner edge of the pavement.
•The attainment of superelevation is done in two stages:
1.Elimination of the crown of camber section
2.Rotation of pavement to attain full superelevationJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

STAGE-1: ELIMINATION OF CROWN OF CAMBERED SECTION:
It can also be achieved by two methods:
a)In first method, outer half of the cross-slope is rotated about the crown at
desired rate, to attain the superelevation of inner half and centreline is not
altered.
b)In second method, (DIAGONAL CROWN METHOD), crown is shifted
progressively outwards, thus increasing the width of the inner half of cross-
section. (Negative superelevation is increased which is not safe for slow moving
vehicle).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

STAGE-2: ROTATION OF PAVEMENT TO ATTAIN FULL
SUPERELEVATION:
•When the crown of the camber is eliminated, it does not signify the superelevation
desired at that section is attained.
•If desired superelevation is more than camber/ cross-slope, the pavement section
is rotated further till the desired elevation is attained.
•Desired superelevation can be attained by two methods:
1.By rotating the pavement cross-section about the centreline, depressing the
inner edge and raising the outer edge, each by half the total amount of
superelevation required.
2.By rotating the pavement cross-section about inner edge of the pavement
raising both centreas well as the outer edge of the pavement, such that the outer
edge is raised by full amount of superelevation desired.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

From 1 to 3, drainage problem will occur.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•In cases where T-curve cannot be provided for some reason, two-third of
superelevation may be attained at straight portion before the start of the circular
curve and the balance one-third is provided at the beginning of the curve.
•The superelevation is introduced by the raising of outer edge of pavement at a rate
not exceeding 1 in 150 in plain and rolling, and 1 in 60 in mountaneousand
steep terrain.
Rotation about centreline Rotation about inner edge
1. It may interfere with drainage system1. No interference with drainage system
2. Centre line remains unchanged 2. Centre line is elevated
3. earthwork is balanced in filling and cutting3. Filling is requiredJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. If a road surface is adequately super-elevated on horizontal curve, which one of
the following is the proper distribution of pressure on the vehicle wheels?
a)Pressure on both outer and inner wheels is equal.
b)Pressure on inner wheels is more than the outer wheels
c)Pressure on inner wheels is less than the outer wheels
d)Pressure on front wheels is thrice the pressure on rear wheels
[IES: 2007]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. What is the maximum superelevation that is fixed by Indian Road Congress
(IRC) for roads in plain and rolling terrain and in snowbound areas, taking mixed
traffic into consideration?
a)10.0%
b)5.5%
c)4.0%
d)7.0%.
[SSC: 2018]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. A superelevation ‘e’ is provided on a circular horizontal curve such that a vehicle
can be stopped on the curve without sliding. Assuming a design speed ‘v’ and
maximum co-efficient of side friction ‘f
max’, which one of the following criteria
should be satisfied?
a) e≤f
max.
b) e > f
max
c) No limit of ‘e’ can be set
d) e=
1−(f
max)
2
f
max
[GATE: 2017]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The rate of equilibrium superelevation on a road is:
1.Directly proportional to the square of vehicle velocity
2.Inversely proportional to the radius of the horizontal curve
3.Directly proportional to the square of the radius of the horizontal curve
Which of the above statements are correct?
a)1 and 2 only.
b)1 and 3 only
c)2 and 3 only
d)1, 2 and 3
[IES: 2018]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. If superelevation is not provided on a horizontal curve of a highway, then on
which portion of the road, are pot holes likely to develop?
a)Outer edge of road.
b)Inner edge of road
c)Centre of road
d)Shoulder of road
[IES: 2010]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. With all other relevant conditions remaining the same, the speed of a vehicle
negotiating a curve is proportional to
a)Weightofthevehicle
b)Weight of the vehicle
c)
1
Weightofthevehicle
d)
1
Weightofthevehicle
.
[IES: 2011]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

RADIUS OF HORIZONTAL CURVE
•Horizontal curve of highways are designed for specified design speed (ruling and
minimum).
•However, if this is not possible due to site conditions, then horizontal curve may
be re-designed.
•On the basis of speed, it is classified into following:
A.RULING MINIMUM RADIUS (RMR)
e+f=
V
2
127RMR
&#3627408401;&#3627408396;&#3627408401;=
&#3627408405;
&#3627409360;
&#3627408414;
&#3627408422;&#3627408410;&#3627408433;+&#3627408415;&#3627409359;&#3627409360;&#3627409365;
Where, V = Ruling design speed (kmph)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

B.ABSOLUTE MINIMUM RADIUS (AMR)
e+f=
V
2
127AMR
&#3627408384;&#3627408396;&#3627408401;=
&#3627408405;
&#3627409360;
&#3627408414;
&#3627408422;&#3627408410;&#3627408433;+&#3627408415;&#3627409359;&#3627409360;&#3627409365;
Where, V = Minimum design speed (kmph)
C.RADIUS BEYOND WHICH NO SUPERELEVATION IS REQUIRED
It is the radius corresponding to which camber serves the purpose of superelevation.
e = camber; f = 0; V = 75% V
d
&#3627408401;
&#3627408401;&#3627408385;&#3627408397;&#3627408402;=
&#3627408405;
&#3627409360;
&#3627409360;&#3627409360;&#3627409363;×&#3627408386;&#3627408410;&#3627408422;&#3627408411;&#3627408414;&#3627408427;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

WIDENING OF PAVEMENT ON HORIZONTAL
CURVE
•On horizontal curve, which are not of very large radius, common practice is to
widen the pavement slightly more, than the normal width.
•The object of providing this extra widening on horizontal curve is as follows:
a)To avoid the off-tracking of vehicle:
•An automobile has a rigid axle and only the front wheels can be turned, hence
when the vehicle takes a turn to negotiate horizontal curve, the rear wheel do not
follow the same path as that of front wheel.
•If no lateral skidding of rear wheels takes place, the rear wheels follows the inner
path on the curve as compared to front wheels.
•This implies if inner front wheels takes a path on the inner edge of pavement on
horizontal curve, the inner rear wheels will be off the pavement of inner shoulder
and vice-versa.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

b)To encounter psychology of the driver:
To maintain clearance between the opposite moving vehicles or overtaking vehicle.
c)To avoid lateral skidding
d)To increase the visibility at the curve
NOTE: Extra widening is the function of length of wheel base (l), radius of curve
(R), and psychological factor.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The extra widening of the pavement on horizontal curve is divided into two parts:
a.Mechanical widening
b.Psychological widening
OFF-TRACKING OF THE VEHICLE:
R
2
2
= R
1
2
+ L
2
Also, R
2–R
1=W
m
W
m=
L
2
2R
2−W
m
2R
2>> W
m, 2R
2–W
m≈2R
Where, R = Radius of curve
&#3627408406;
&#3627408422;=
&#3627408395;
&#3627409360;
&#3627409360;&#3627408401;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

For ‘n’ lane roads,
&#3627408406;
&#3627408422;=
??????&#3627408395;
&#3627409360;
&#3627409360;&#3627408401;
NOTE: Hence, in a road having ‘n’ traffic lanes as ‘n’ vehicles can travel
simultaneously, W
mrequired will be more.
Length of wheel base = l = 6.1m
PSYCHOLOGICAL WIDENING
At horizontal curve, drivers have the tendency to maintain a greater clearance
between the vehicles, than a straight stretch of road. Therefore, an extra width is
required for this, which is given empirically by following relation:
&#3627408406;
&#3627408425;=
&#3627408405;
&#3627409367;.&#3627409363;&#3627408401;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Where, V = design speed (kmph)
R = Radius (m)
Hence, total widening = W
e= W
m+ W
p
&#3627408406;
&#3627408414;=
??????&#3627408395;
&#3627409360;
&#3627409360;&#3627408401;
+
&#3627408405;
&#3627409367;.&#3627409363;&#3627408401;
NOTE: 1. For single lane road and two-lane road, if radius is greater than 300m,
then extra widening is not required.
2. For single lane road, psychological widening is not considered (W
p= 0).
3. Extra widening is provided gradually through transition curve.
4. Generally, extra widening is provided equally on both the sides of curve. But, on
hilly roads, extra widening is provided only on inner side.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Extra width of the pavement at horizontal curve are as follows:
Radius of curve (m)≤20m20 –40m41 –60m61 –100m101 –300m> 300m
Extra width on two-
lane road
1.5 1.5 1.2 0.9 0.6 -
Extra width on single
lane road
0.9 0.6 0.6 - - -Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

The widening is introduced gradually starting from the tangent point, i.e. beginning
of T-curve at uniform rate equally on both sides in plain terrain and on inner side on
hilly terrain such that designed widening is attained at end of the transition curve.
On horizontal circular curve, without T-curve, two-third of the widening is
provided at the end of the straight portion and remaining one-third widening is
provided on circular curve.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Extra-widening of pavements provided because of off-tracking is known as:
a)Psychological widening
b)Mechanical widening.
c)Physical widening
d)Frictional widening
[SSC: 2018]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

HORIZONTAL TRANSITION CURVE
•T-curve is provided to change the alignment of pavement from straight to circular
gradually.
•The T-curve has a radius which decreases from infinity at the tangent point to the
designed radius of circular curve.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OBJECTIVES OF PROVIDING THE TRANSITION CURVE
1.To introduce centrifugal force gradually over the vehicle.
2.To reduce the sudden jerk.
3.To introduce superelevation and extra widening gradually.
4.To improve the aesthetic appearance of road.
NOTE: 1. For an ideal T-curve, the length of the curve should be inversely
proportional to the radius.
&#3627408395;∝
&#3627409359;
&#3627408401;
LR = constant
At TP, R = ∞, L = 0
At CC, R = R
c, L = L
sJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

For transition curve to be provided, following options are available:
1.Spiral
2.Lemniscate
3.Cubical parabola
•All the three curves follow same path uptodeflection angle of 4
o
and are almost
same upto9
o
.
•In all these curves, radius decreases as length increases.
•But, the rate of change of radius or rate of change of centrifugal force is not
constant in case of lemniscate and cubical parabola.
•Hence, “Spiral curve” is used as transition curve as it fulfils the basic requirement
of ideal transition curve. Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

LENGTH OF TRANSITION CURVE
Length of the transition curve is designed to fulfil three requirements:
A.RATE OF CHANGE OF CENTRIFUGAL FORCE
•Length of the transition curve is designed such that the rate of change of
centrifugal force is low.
•Rate of change of acceleration, c=
∆a
T
=
a
f−a
i
T
=
(0.278V)
3
LsRs
&#3627408395;
&#3627408428;=
&#3627409358;.&#3627409358;&#3627409360;&#3627409359;&#3627409363;&#3627408405;
&#3627409361;
&#3627408386;&#3627408401;
Where V = Design speed (kmph)
•The maximum allowable value of rate of change of acceleration ‘c’ without
producing discomfort to the vehicle/ passenger is given by:
&#3627408412;=
&#3627409366;&#3627409358;
&#3627409365;&#3627409363;+&#3627408405;
&#3627409358;.&#3627409363;−&#3627409358;.&#3627409366;&#3627408422;/&#3627408428;&#3627408414;&#3627408412;
&#3627409361;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

B.RATE OF INTRODUCTION OF SUPERELEVATION (N)
Let rate of introduction of superelevation is 1V: NH
As per IRC:
1.1:150 for Plain/ rolling terrain
2.1:100 for built-up areas
3.1:60 for mountaneous/ steep terrain
Hence, length of TC = Nx
Where, x = elevation of outer edge
CASE-I: If rotation is done about centre-line
tanθ=
x
w+w
e
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&#3627408433;=
&#3627409359;
&#3627409360;
&#3627408414;(&#3627408432;+&#3627408432;
&#3627408414;)
&#3627408395;
&#3627408428;=
&#3627409359;
&#3627409360;
&#3627408414;&#3627408432;+&#3627408432;
&#3627408414;&#3627408397;=
&#3627408397;&#3627408388;
&#3627409360;
CASE-II: If rotation is done about inner edge
tanθ=
x
w+w
e
X = e (w + w
e)
&#3627408395;
&#3627408428;=????????????=&#3627408414;&#3627408432;+&#3627408432;
&#3627408414;&#3627408397;=&#3627408397;&#3627408388;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

C.AS PER IRC
As per IRC, length of horizontal T-curve is given by following empirical
relationship:
a)For plain and rolling terrain:
&#3627408395;
&#3627408428;=
&#3627409360;.&#3627409365;&#3627408405;
&#3627409360;
&#3627408401;
b)For mountaneousand steep terrain:
&#3627408395;
&#3627408428;=
&#3627408405;
&#3627409360;
&#3627408401;
Where, V= design speed (kmph)
Length of T-curve to be provided is maximumof three calculated from previous
criteria.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which one of the following conditions is not correct with respect to transition
curve?
a)It should be tangential to the straight approaches at the two ends
b)It should meet the circular curve tangentially
c)Its curvature will necessarily be non-zero at the point of take-off from the
straight approaches.
d)The rate of increase of curvature along the transition reach should match with
the increase of cant
[IES: 2019]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Full amount of superelevation on a horizontal curve is provided at the
a) Beginning of the transition curve
b) Centre of the circular curve
c) End of the transition curve.
d) Centre of the transition curve
[IES: 2010]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The following purposes served by a transition curve in a highway alignment
include:
1.Gradual introduction of the centrifugal force on moving vehicles from zero on
the straight alignment to a constant final value on the circular curve
2.Enabling the gradual introduction of superelevation on the roadway
Select the correct answer using the codes given below:
a)1 only
b)2 only
c)Both 1 and 2.
d)Neither 1 nor 2
[IES: 2017]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. An ideal horizontal transition curve is a:
a)Parabola
b)Circle
c)Spiral.
d)Hyperbola
[IES: 2012]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which of the following are requirements for the design of a transition curve for a
highway system?
1.Rate of change of grade
2.Rate of change of radial acceleration
3.Rate of change of superelevation
4.Rate of change of curvature
Select the correct answer using the code given below:
a)1, 2 and 3
b)2, 1 and 4
c)1, 3 and 4
d)2, 3 and 4.
[IES: 2005]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Consider the following statements:
A transition curve is provided on a circular curve on a highway to provide:
1.Gradual introduction of centrifugal force
2.Minimum stopping sight distance
3.Gradual introduction of superelevation
4.Comfort and security to passengers
Which of the statements given above are correct?
a)1, 2 and 3
b)1, 3 and 4.
c)2, 3 and 4
d)1, 2 and 4
[IES: 2004]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The relationship between the length (l) and radius (r) of an ideal transition curve
is given by:
a)l∝r
b)l∝r
2
c)l∝
1
r
.
d)l∝
1
r
2
[GATE: 1999]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

SETBACKDISTANCE
•It is the clearance distance required from the centreline of pavement/ road to the
obstruction in order to maintain the adequate sight distance to the curve.
•The setback distance or clearance which is required from the centreline of
horizontal curve depends upon:
1.Required sight distance
2.Radius of horizontal curve
3.Length of the curve (L
cc)
CASE-I: When L
cc> SD
(a)For narrow roads such as single lane road:
O = Obstruction
AB = Sight lineJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OD = m = setback distance
m = CD –CO = R –CO
Arc length AD = R×
α
2
α=
SD
R
×
180°
π
degrees
In ∆ACO,
cos
α
2
=
OC
R
CO=Rcos
α
2
m=R−Rcos
α
2
&#3627408422;=&#3627408401;&#3627409359;−&#3627408412;&#3627408424;&#3627408428;
&#3627409090;
&#3627409360;
NOTE: SD is calculated along the centreline of road in single lane road
m = set-back distance measured from centrelineJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b) Wide roads/ two or more lane roads:
•Here, the stopping distance is measured along the centreline of the inner lane and
the setback distance is measured from the centreof the road.
•Let ‘d’ be the distance between the centreline of the road and centrelineof the
inside lane.
CA = R –d
CB = R –d
DO = m = setback distance
d=
w+w
e
4
α=
SD
(R−d)
×
180°
π
degreesJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

m = CD –OC = R –(R –d) cos
α
2
&#3627408422;=&#3627408401;&#3627409359;−&#3627408412;&#3627408424;&#3627408428;
&#3627409090;
&#3627409360;
+&#3627408413;&#3627408412;&#3627408424;&#3627408428;
&#3627409090;
&#3627409360;
Set back distance from:
1.Outer edge of outer lane = m + 2d
2.Centre of outer lane = m + d
3.Centre of inner lane = m –d
4.Inner edge of inner lane = m –2d
CASE-II: When L
cc< SD
(a)For narrow roads such as single lane road:
OF = m = Set-back distance
m = FO = FG + GOJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

α=
L
cc
R
×
180°
π
degrees
FG = R (1 -cos
α
2
)
GO =
SD−Lcc
2
sinΤ
α
2
&#3627408422;=R(1−&#3627408412;&#3627408424;&#3627408428;
&#3627409090;
&#3627409360;
)+
&#3627408402;&#3627408387;−&#3627408395;
&#3627408412;&#3627408412;
&#3627409360;
&#3627408428;&#3627408418;&#3627408423;ൗ
&#3627409090;
&#3627409360;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b) Wide roads/ two or more lane roads:
α=
L
cc
(R−d)
×
180°
π
degrees
&#3627408422;=R(1−&#3627408412;&#3627408424;&#3627408428;
&#3627409090;
&#3627409360;
)+
&#3627408402;&#3627408387;−&#3627408395;
&#3627408412;&#3627408412;
&#3627409360;
&#3627408428;&#3627408418;&#3627408423;ൗ
&#3627409090;
&#3627409360;
+&#3627408413;&#3627408412;&#3627408424;&#3627408428;ൗ
&#3627409090;
&#3627409360;
NOTE: Set-back distance from centreline of inner lane = m –d
Set-back distance from centreline of outer lane = m + dJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

CURVERESISTANCE
•The automobiles are steered by turning the front wheels but the rear wheels do not
turn.
•When a vehicle is driven by rear wheel on a horizontal curve, the direction of
rotation of rear and front wheel are different.
•If tractive force ‘T’ is provided to the rear wheel in direction normal to its axis,
then the tractive force available for the front wheel is Tcosα, where αis angle of
turn.
•Hence, loss of tractive force due to turning
of vehicle on horizontal curve is
T -T&#3627408412;&#3627408424;&#3627408428;&#3627409090;, termed as “Curve Resistance”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

VERTICALALIGNMENT
•The natural ground may be level at some places and may have slope of different
magnitude at other locations.
•Generally, highway is aligned to follow the natural topography keeping in view
the drainage and other design considerations.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The vertical alignment of the highway affects:
1.Acceleration and deacceleration
2.Operational cost of vehicle
3.Speed
4.Sight distance
5.Comfort while driving
The vehicle alignment consists of two elements:
1.Gradient
2.Vertical curveJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

GRADIENT
•It is defined as change in elevation/ height of road along the road or may be
defined as rise or fall along the length of road w.r.t.horizontal.
•It can be represented as follows:
1.1 in x
2.
1
x
×100%
3.Tanα
NOTE: The angle which measures change in direction at the intersection of two
grades is called as “deviation angle”.
N=α
1+α
2
Or,
N=α
1−α
2Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TYPES OF GRADIENT
Gradient are of following types:
1.RULING GRADIENT/ DESIGN GRADIENT:
•It is the maximum gradient with which the designer attempts to design the vertical
profile of the road.
•Gradients uptoruling gradient are adopted as a normal course in design.
•However, flatter gradients may be preferred wherever it can be provided.
2.LIMITING GRADIENT:
•Wherever topography of a place forces to adopt steeper gradient than ruling
gradient, it can be extended uptolimiting gradient, or else enormous cost of
construction would be observed.
•However, the length of road on which this gradient is provided is limited.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

3.EXCEPTIONAL GRADIENT:
•In some extreme situations, it may be unavoidable to provide still steeper gradient than
limiting gradient for short stretches of road, in such cases, exceptional gradient can be
provided but upto100mat a stretch.
•As per IRC, values of different gradients are as follows:
Type of terrain Ruling gradientLimiting gradientExceptional gradient
Plain or rolling 1 in 30 1 in 20 1 in 15
Mountaneousand steep terrain
having RL more than 300m above
MSL
1 in 20 1 in 16.7 1 in 14.3
Steep terrain uptoRL 300m above
MSL
1 in 16.7 1 in 14.3 1 in 12.5Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: Above 300m, oxygen is less, so it is difficult in combustion of engine,
hence, optimum power is not generated.
4.MINIMUM GRADIENT
•The minimum gradient to be provided from drainage point of view in order to
allow gravity flow of water (rain) inside the drainage system is termed as
“minimum gradient”.
•As per IRC, minimum gradient are as follows:
1.Concrete drain: 1/500 (0.2%)
2.Kutcha/ soil drain: 1/200 (0.5%)
•Depending upon type of soil, it can be taken up to 1/100 (1%) (highly permeable
soil).
NOTE: EG > LG > RG/DG > MGJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

GRADE COMPENSATION ON HORIZONTAL
CURVE
•At horizontal curve, due to the turning angle of vehicles with rear wheel drive,
curve resistance of (T –T cosα) is developed.
•When there is horizontal curve in addition to the gradient, there will be increased
resistance due to both horizontal curve (curve resistance) and gradient (grade
resistance).
•Total resistance = Grade + Curve
•Hence, when sharp horizontal curve is introduced on a road which has already the
maximum permissible gradient (ruling), the reduction in the gradient is to be
carried out.
•This restriction in gradient at horizontal curve is termed as “Grade
Compensation”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

????????????%=
30+??????
??????
Where, R = Radius of horizontal curve (m)
•The maximum value of GC is limited to (75/R) as per IRC. Thus,
GC = min (i)
&#3627409361;&#3627409358;+??????
??????
(ii) 75/R
•GC is not necessary for gradient flatter than 4%. Hence, it is not being provided
beyond (less than) 4%.
NOTE: When camber and gradient is provided together to the road, water flows in
direction resultant to the camber known as “Hydraulic Gradient”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. ASSERTION (A): When a sharp horizontal curve is to be introduced on a road
which already has the maximum permissible gradient, the gradient should be
decreased
REASON (R): The gradient should be decreased to compensate for the loss of
tractive effort due to the introduction of sharp horizontal curve on the road
a) Both A and R are true and R is correct explanation of A.
b) Both A and R are true and R is not a correct explanation of A
c) A is true but R is false
d) A is false but R is true
[IES: 2001]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

VERTICAL CURVE
•Due to change in vertical alignment of road, it is necessary to introduce vertical
curve at the intersection of different grades to smoothen out the ride.
•These curves are broadly classified into two:
•Convexity upward
SUMMIT/ CREST
CURVE
•Concavity upward
VALLEY/ SAG
CURVEJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

SUMMITCURVE
These are vertical curves with convexity upward and concavity downward.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Summit curve is formed by two gradients, starting and end gradient as follows:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Significant points regarding summit curves are:
1.Vertical point of Intersection (VPI) always lies above the curve.
2.Summit curves are designed only for “sight distance” criteria. Minimum SSD
must be provided but it is desirable to provide OSD. If OSD is not possible, then
go for ISD.
3.When a fast moving vehicle travels along a summit curve, centrifugal force acts
upwards against gravity, hence, effective weight of vehicle is reduced. Thereby,
pressure on tyreand suspension are relieved. Hence, there is no problem of
discomfort.
4.Since design of summit curve is governed by stopping distance or sight distance
criteria, “circular curve” is ideal for this, as the sight distance in this case
remains constant. Hence, it is available throughout the curve.
5.The deviation angles in vertical curve are very small, hence a simple
“parabola” or “square parabola ” is nearly analogous to circular arc, also a
parabola is easy to manipulate mathematically for computation. Moreover, it
offers good riding comfort. Hence, being provided practically.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ANALYSIS OF SUMMIT CURVE
•This curve is non-symmetrical as n
1≠n
2.
(1)GENERAL EQUATION
y’ = ax
2
+ bx + c
At point A: x = 0; y’ = 0
Hence, c = 0
dy′
dx
=2ax+b(gradientorslope)
At point A: x = 0;
dy′
dx
=n
1
Hence, n
1= b
At point B: x = L
s;
dy′
dx
=-n
2
hence, a=
−N
2L
sJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

y’ = ax
2
+ bx + c
&#3627408434;
′
=
−&#3627408397;
&#3627409360;&#3627408395;
&#3627408428;
&#3627408433;
&#3627409360;
+&#3627408423;
&#3627409359;&#3627408433;
This is the “General Equation” in parameters x and y’.
(2)POSITION OF SUMMIT/ CREST/ HIGHEST POINT OF CURVE FROM
VPC
For maximum y’,
dy′
dx
=0
&#3627408433;=
&#3627408423;
&#3627409359;&#3627408395;
&#3627408428;
&#3627408397;
(3)APEX EQUATION
Here, apex means parameters above the road or ground, i.e. (x and y)
At A, tanθ= n
1Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

&#3627408486;+&#3627408486;′
&#3627408485;
=??????
1
y = n
1x –y’
y = n
1x +
N
2Ls
x
2
-n
1x
y =
&#3627408397;
&#3627409360;&#3627408395;
&#3627408428;
&#3627408433;
&#3627409360;
(4)POSITION OF VPI FROM VPC
In ∆AVE,tanθ
1=n
1=
VE
x
VE = n
1x…….(i)
In ∆VBD,tanθ
2=n
2=
VD
(Ls−x)
VD = n
2(L
s–x)…..(ii)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

y′
B=
−N
2L
s
L
s
2
+n
1L
s=
−N
2
L
s+n
1L
s
y′
B=VE−VD
&#3627408433;=
&#3627408395;
&#3627408428;
&#3627409360;
The above equation is valid for both symmetrical and unsymmetrical curves.
NOTE: 1. WHEN CURVE IS SYMMETRICAL:
•Vertical line passing through VPI will bisect the length of curve (L
s) in two equal
halves.
•This line will always pass through summit point of the curve.
•In this case, RL of starting point and end point will be same.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE: 2. WHEN CURVE IS UNSYMMETRICAL:
•Vertical line passing through VPI will bisect the length of curve in two equal
halves.
•This line will never pass through summit point of the curve.
•In this case, RL of starting and end points are different and the curve will be lifted.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

LENGTH OF SUMMIT CURVE
•While designing the length of parabolic summit curve, it is necessary to consider
SSD or OSD respectively
CASE-I: Length of Summit curve for SSD:
(a)L
s> SSD
&#3627408395;=
&#3627408397;&#3627408402;
&#3627409360;
(&#3627409360;&#3627408391;+&#3627409360;&#3627408417;)
&#3627409360;
(From apex equation)
Where S = sight distance
L = L
s= Length of summit curve
As per IRC, H = 1.2m, h = 0.15m
&#3627408395;=
&#3627408397;&#3627408402;
&#3627409360;
&#3627409362;.&#3627409362;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b)L
s< SSD
&#3627408395;=&#3627409360;&#3627408402;−
(&#3627409360;&#3627408391;+&#3627409360;&#3627408417;)
&#3627409360;
&#3627408397;
As per IRC,
&#3627408395;=&#3627409360;&#3627408402;−
&#3627409362;.&#3627409362;
&#3627408397;
CASE-II: Length of Summit curve for OSD:
(a)L
s> OSD
&#3627408395;=
&#3627408397;&#3627408402;
&#3627409360;
(&#3627409360;&#3627408391;+&#3627409360;&#3627408417;)
&#3627409360;
(From apex equation)
Where S = sight distance
L = L
s= Length of summit curve
As per IRC, H = 1.2m, h = 1.2m
&#3627408395;=
&#3627408397;&#3627408402;
&#3627409360;
&#3627409367;.&#3627409364;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b)L
s< OSD
&#3627408395;=&#3627409360;&#3627408402;−
(&#3627409360;&#3627408391;+&#3627409360;&#3627408417;)
&#3627409360;
&#3627408397;
As per IRC,
&#3627408395;=&#3627409360;&#3627408402;−
&#3627409367;.&#3627409364;
&#3627408397;
NOTE: 1. While calculating the length of summit curve, first assume case –(a) L
s>
SD, if it fails, then go for case –(b).
2. When deviation angle are strong, the length of summit curve generally works out
to be less than sight distance.
3. In very small deviation angle (N), the length of summit curve works out to be
negative, indicating that there is no problem of sight restriction at the summit curve.
4. For calculating SD (SSD and OSD), the effect of gradient is not to be considered.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

5. The minimum radius of the curve ‘R’ is given by:
&#3627408401;=
&#3627408395;
&#3627408397;
6. The minimum length of vertical curve for different speeds and for maximum
grade change which do not require vertical curve as per IRC are given as follows:
Design speed (kmph) Maximum grade change (%) not
requiring a vertical curve
Minimum length of
vertical curve
35 1.5 15
40 1.2 20
50 1.0 30
65 0.8 40
80 0.6 50
100 0.5 60Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The length of summit curve on a two-lane two-way highway depends upon
a)Allowable rate of change of centrifugal acceleration
b)Coefficient of lateral friction
c)Required stopping sight distance
d)Required overtaking sight distance.
[GATE: 2005]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The ideal form of the curve for the summit curve is:
a)Spiral
b)Parabola
c)Circle.
d)Lemniscate
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VALLEYCURVE
•These are the vertical curve with concavity upward and convexity downward.
•It is also formed by two gradients in following ways:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Some important points of reference for valley curve are:
1.VPI always lie below the curve.
2.As fast moving vehicle negotiate valley curve, the centrifugal force developed
acts downward in addition to the self-weight, thus additional pressure on the
suspension system is created. Hence, discomfort to the passengersdue to
impact is created.
3.In order to avoid discomfort due to impact caused by centrifugal force acting
downward, the rate of change of centrifugal acceleration should be induced
gradually along the valley curve.
4.For this, transition curve is to be provided. Infact, valley curve is formed by
joining two T-curves.
NOTE: “Cubic parabola” is generally preferred in valley curve.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

5.During night driving, the visibility ahead is dependent on head light of vehicles,
when the road lightening is not adequate.
6.There is restriction of SD at valley curve as the head light gets intercepted by the
ascending portion of the curve.
7.Hence, in this case, SSD must be equal to HSD (Headlight Sight Distance).
8.However, there is no problem of OSD during night time as other vehicles with
head light can be seen from considerable distance.
9.In India, minimum height of head light is considered to be 0.75m.
h = 0.75m
β= Beam angle = 1
oJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Valleys curves are designed taking following considerations into account:
1.Comfort to passengers
2.SSD at night (HSD)
3.Drainage in the valley curve at lower most point
4.Aesthetic considerations
A.POSITION OF LOWEST POINT OF VALLEY CURVE FROM
STARTING OF THE CURVE (VPC)
&#3627408433;=
&#3627408423;
&#3627409359;
&#3627409360;&#3627408397;
ൗ
&#3627409359;
&#3627409360;
&#3627408395;
&#3627408431;
Where, L
v= length of valley curveJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

B.LENGTH OF VALLEY CURVE
The valley curve and its length are designed as transition curve to fulfill two criteria:
a)Allowable rate of change of acceleration
b)Required HSD at night
•The maximumof two values is adopted
•Generally, second criteria i.e. HSD is higher, hence, it governs the design of the
valley curve.
I.Length of valley curve from comfort condition:
L
s= length of T-curve =
v
3
CR
R=
L
s
N
=
L
v
2N
&#3627408395;
&#3627408431;=&#3627409360;
&#3627408397;&#3627408431;
&#3627409361;
&#3627408386;
ൗ
&#3627409359;
&#3627409360;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

C is taken to be 0.6 m/s
3
and when design speed (V) is taken in kmph:
&#3627408395;
&#3627408431;=&#3627408397;&#3627408405;
&#3627409361;
(&#3627408422;)
II.Length of valley curve from HSD Criteria:
Case (i): L > HSD
For case of simplicity, we assume the valley curve to be simple parabola.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

y=
N
2L
v
x
2
When x = S, y = h + S tanβ
h + S tanβ=
N
2L
v
S
2
&#3627408395;
&#3627408431;=
&#3627408397;&#3627408402;
&#3627409360;
&#3627409360;(h+S&#3627408429;&#3627408410;&#3627408423;&#3627409091;)
As per IRC, h = 0.75m, β= 1
o
&#3627408395;
&#3627408431;=
&#3627408397;&#3627408402;
&#3627409360;
&#3627409359;.&#3627409363;+0.035S)
Case (i): L < HSD
h + S tanβ= S−
L
v
2
NJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

&#3627408395;
&#3627408431;=&#3627409360;&#3627408402;−
&#3627409360;(&#3627408417;+&#3627408402;&#3627408429;&#3627408410;&#3627408423;&#3627409091;)
&#3627408397;
As per IRC, h = 0.75m, β= 1
o
&#3627408395;
&#3627408431;=&#3627409360;&#3627408402;−
&#3627409359;.&#3627409363;+&#3627409358;.&#3627409358;&#3627409361;&#3627409363;&#3627408402;
&#3627408397;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which of the following are the criteria associated with the design of sag vertical
curve?
1.Provision of minimum stopping distance during day time
2.Adequate drainage
3.Comfortable operation
4.Pleasant appearance
Select the correct answer using the codes given below:
a)1, 2 and 4
b)2 and 3
c)2, 3 and 4.
d)1 and 3
[IES: 1996]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which one of the following statement is correct?
a)The radius of transition raises from infinity to a selected minimum in order to
attain full superelevation and curvature gradually.
b)The compound curve is an arc of a circle
c)The radius of transition curve is constant for entire length
d)The horizontal curves are provided whenever there is a change in gradient
[IES: 2020]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Light reflecting devices used to guide the driver along the proper alignment are
called:
a)Rumble strips
b)Delineators.
c)Attenuators
d)Litter bin
[IES: 2010]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Match List-I with List-II and select the correct answer using the codes given below the lists:
(adopting standard notations)
Codes: A B C D
a) 1 2 3 4
b) 3 4 1 2
c) 1 5 2 4
d) 4 2 3 1.
[IES: 1996]
List-I List-II
A. Cubic parabola equation
1.
??????&#3627408454;
2
4.4
B. Shift in transition curve
2.
??????
2
24&#3627408453;
C. Valley curve
3.
??????&#3627408454;
2
1.5+0.035&#3627408454;
D. Summit curve
4.
??????
3
6&#3627408453;??????
5.
??????
2
??????&#3627408453;Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Which one of the following expressions gives Intermediate Sight Distance as per
IRC standards? [SSD = Stopping sight distance; OSD = Overtaking sight distance]
a)2 SSD.
b)
(SSD+OSD)
2
c)
(OSD−SSD)
2
d)2 OSD
[IES: 1999]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. The curve provided at the change of gradient is called:
a)Horizontal curve
b)Transition curve
c)Reverse curve
d)Vertical curve.
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Q. Superior the road,
a)Steeper is the cross-slope or camber
b)Gentler is the camber.
c)Steeper is the superelevation
d)Lesser is the cost
[GATE: 1987]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. Consider the following statements in the context of geometric design of roads:
1.A simple parabolic curve is an acceptable shape for summit curves
2.Comfort to passengers is an important consideration in the design of summit
curves
The correct option evaluating the above statements and their relationship is:
a)1 is true, 2 is false.
b)1 is true, 2 is true and 2 is the correct reason for 1
c)1 is true, 2 is true and 2 is not the correct reason for 1
d)1 is false and 2 is true
[GATE: 2010]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TRAFFIC ENGINEERING
JASPAL SIRJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

CHAPTER-03
•It deals with improvement of traffic performance on road network through
systematic traffic studies analysis, planning, administration and engineering
application.
•Here traffic performance represent:speed, safety, cost and efficiency of traffic
movement.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Traffic engineering deals with following characteristics
(a) TRAFFIC CHARACTERISTICS
(b) TRAFFIC STUDIES
(c) TRAFFIC PLANNING AND STUDIES
(d) GEOMETRIC DESIGN
(e) REGULATION, CONTROL AND OPERATION
(f) ROAD SAFETY ASPECTS
(g) TRAFFIC MANAGEMENT AND ADMINISTRATIONJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

A. TRAFFICCHARACTERISTICS
•Characteristics of traffic are further governed by
(i)Road user characteristics
(ii)Vehicular characteristics
(i) ROAD USER CHARACTERISTICS :
•It involves all action of road user either as pedestrian, cyclist, cart driver or motorist or
PCU driver.
•The various factors which affects the road used actions are as follows:
(a) PHYSICAL-Physical characteristics of road user may either be permanent or
temporary.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•PermanentCharacteristics-VISION, HEARING, STRENGTH, GENERAL
REACTION TO SITUATION.
6/6 vision or normal vision.
It is an ability of a person to recognize a letter of size 8.5 mm from a distance of 6m.
6/9 Vision -This vision corresponds to poor vision.
Here person is able to recognize the object (8.5 mm letter) from distance of 6m
instead of 9m.
10/6 vision -Supervision. (Practically it is not possible).xActual distance
Vision = For a normal eye
yRequired distance
=→ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TemporaryCharacteristics-Affecting their efficiency are FATIGUE,
DRUGS INTAKE, ILLNESS.
•All these will increase the reaction time of driver.
(b) MENTAL FACTORS -It includes knowledge, skill, intelligence, experience
and literacy of road user which govern its behavior on road.
(c) PHYSHOLOGICAL FACTORS -These effects reaction to traffic situations of
road users to great extent.
•It includes attentiveness, fear, anger, superstition ill parents, general attitude
towards traffic and regulations.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(d) ENVIRONMENTAL FACTORS -It includes traffic stream characteristics,
roadside feature, atmospheric condition and locality.
(ii) VEHICULARCHARACTERISTICS -
•These characteristics are further classified into
(a)Static characteristics
(b)Dynamic characteristics
(a)STATIC-Static characteristics which affect the road design are:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(i)Dimension →length, breadth, height
(ii)Turning angle
(iii)Total weight of vehicle
(iv)Ground clearance
(i) DIMENSION -length of the vehicle will control horizontal alignment of the
road, extra widening, parking facilitated.
•Height of vehicle controls height of bridge, height of cables lines, other service
line, overhead sign boards under pass.
•Width of vehicle governs lane width, shoulder width, parking design.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii) Turning angle -governs curve resistance, Radices
(iii) Wt. of vehicle -governs thickness of pavement, gradient of road.
(iv) Ground clearance -decides the nt. Of bumps, approaches i.e, ramp.
(b) DYNAMIC -Characteristics includes-
•Power of vehicle decides gradient of road, hauling capacity, rolling resisting.
•Speed of vehicle governs geometric design elements.
(c) BREAKING -governs sight distance, efficiency breaking, deceleration, impact
on road materialJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Braking characteristics of vehicle depends on design and type of braking system.
Eg-Mechanical, fluid, air brakes which can be determined by performing brake
test.
In this test brakes are applied till the vehicle completely stops and two of the three
parameters are noted to find skid resistance.
(a)Braking distance (L)
(b)Initial Speed (u)
(c)Actual duration of brake application (t)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(i)Retardation: v = u + at
0 = u + at
a = -(u/t) deceleration
(ii)Braking distance:
(iii) Skid resistance: 21
Lu at
2
=+ 21u utut
Lu tut
2t 22
−
=+ =−=

 ut1
L initial speed duration of brake
22

== 

 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

F.L force and displacement are opposite.()
2 u
ou2L
t
−
=+ 2
utut
L - (i)
2u2
== KEwork done= 2211
mvmu
22
−= 21
muF.L
2
−=− 21
mu f mg L F = f mg
2
=− 2
u
L - (ii)
2gf
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

From (i) and (ii)2
utu
22gf
= uaRetardation
f
gtgacc. due to gravity
−
=== Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Brakeisappliedonavehiclewhichthenskidsadistanceof16mbeforecoming
tostop.Ifthedevelopedaveragecoefficientoffrictionbetweenthetyresandthe
pavementsis0.4,thenthespeedofthevehiclebeforeskiddingwouldhavebeen
nearly:
a)20 kmph
b)30 kmph
c)40 kmph
d)50 kmph
[IES: 1999]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Avehiclemovingat40kmphspeedwasstoppedbyapplyingbrakeandthe
lengthoftheskidmarkswas12.2m.Iftheaverageskidresistanceofthepavement
is0.70,thebrakeefficiencyofthetestvehiclewillbenearly:
a)80%
b)74%
c)68%
d)62%
[IES: 2019]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

B. TRAFFIC STUDIES AND ANALYSIS
•TEStudiesarecarriedoutforcollectingtrafficdata,foritsanalysistoidentifythe
movementoftrafficalongtheparticularroadsoastoapplyitfortrafficcontrol
measuresandefficientGD.
•The different types of traffic engineering studies are as follows
(i)TRAFFIC VOLUME STUDIES
(ii)TRAFFIC AND CAPACITY ANALYSIS
(iii)SPOT SPEED STUDIES
(iv)ORIGIN AND DESTINATION STUDIES
(v)PARKING STUDIES
(vi)ACCIDENT STUDIESJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

TRAFFIC VOLUME STUDY
•Trafficvolumeisameasuretoquantifythetrafficflowandisexpressedasnoof
vehiclethatpassacrossagivensectionofroadduringunittime.
•Asthecarriagewaywidthoftheroadmayvarythetrafficvolumeisexpressedas
numberofvehiclesperunittimepertrafficlane.
•Differentclassesofvehiclemakeuseofsameroadhenceformixedflowtraffic,
differentclassesofthevehiclemustbetransformed,expressedorconvertedinto
onestandardtypeofunitsuchas“passengercar”.
•Henceeachvehicleclassisassignedanequivalentfactortermedaspassengercar
unit(PCU)whichisdefinedas( )
( )
SV
SV
V/viSpeed ratio
PCUi =
Length Ratio L/Li
 =
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

PCU values recommended by IRC for different vehicles on “urban roads”
VEHICLE TYPE EQUIVALENT PCU
(1)Twowheeler : Scooter, Bike
(2) Passenger Car : Van
(3) Auto rickshaw
(4) LCV
(5) Truck / Bus
(6) Tractor trailer
0.7
1
2
2
3.7
5Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Traffic volume studies are being carried out
oTo decide the priority.
oFor improvement of design
ofor computing roadway capacity
oto plan traffic operations and control
•Traffic volume can be measured by any of the following
(i) MANUALMETHOD -very accurate method in which different class of vehicle
can also be noted, but cannot be used for continuous measurement.
(ii) MECHANICALMETHOD–
(a)RADAR (Radio detection and ranging)
(b)PNEUMATIC SENSORS (Based on pressure applied)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(c) MAGNETIC DETECTOR
(d) CCTV Cameras.
•Traffic volume data can be represented in any of the following forms
(i)AADT (Annual avg daily traffic)
(ii) AAHT(Annual avg hourly traffic)Total no. of vehicles throughout a year
AADT veh/day
365
= Total no. of vehicles throug year
AAHT veh/hr.
36524
=
 AADT
AAHT
24
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) AAWT (Annual avgweekday traffic)
AAWT > AADT Weekday= Monday to Friday.
on weekend volume is considerable reduced.
(iv) ADT (Average daily traffic)
ADT >AADT –Jitnabadasample size utnachotafluctuation.
(v)TRENDCHART:Trafficvolumecanberepresentedinformoftrendchart
whichisusefulinestimatingtherateofgrowthoftrafficofaparticularclassthat
canbeusedforplanningfutureexpansiondesignandregulation.Total no. of vechile throughout week
AAWT veh/day.
525260
=
= Total number of vehicles throughout a week
ADT
7

=

 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Iffromtrendchartrateofgrowthoftrafficvolumeiscomputedtober%,then
futuretrafficisgivenbyJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vi) VARIATION CHART :
•Variationchartcanbeusedtoshow,hourly,dailyorseasonalvariationoftraffic
volume,overaparticularsectionofroad.
•Thischartshelpsindecidingthefacilitiesandregulationneededduringpeak
trafficperiod.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vii) TRAFFIC FLOW MAPS
•Thesemapsalongtheroutesindicatesthevolumeoftrafficflowingthroughthem.
•Thethicknessoflinerepresentsthetrafficvolumetoanydesiredscale.
•Thishelpstofindthetrafficvolumedistributionalongtheexistingroadsata
glance.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(viii) Volume flow diagram at intersection
•Volumeflowdiagramatintersectioneitherdrawntobecertainscaleorindicating
trafficvolumecanbeusedtofindthedetailsofcrossingandturningtraffic.
•ThesedataarerequiredfordesignofintersectionJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ix) 30
th
highest hourly volume data :
•Ifdesigningofaroadisdoneforhighestorpeakhourlyvolumeofayear,itwould
behighlyuneconomical(Q
max)
•Howeverifitisdonefor(AAHV)itwouldnotbesufficientforconsiderable
periodofyeartocarrythetrafficvolumeandwouldleadtocongestionoftheroad.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•30
th
highesthourlytrafficvolumeisthehourlyvolumethatwillbereachedonly
30timesorexceededonly29timesinayear
•AsperIRCifdesigningisdonefor30
th
HHVthenneitheritiscostly,noritis
congested,
•Henceeliminatestheproblemofcongestionformostpartoftheyear.
NOTE : PERIODIC VOLUME COUNT
•In order to find certain traffic data such as AADT, ADT etcit is necessary to count
traffic for long duration of time may be for years and time.
•Counting traffic for long duration of time involves cost and effort which is not
feasible practically. In such case IRC suggest, to make use of technique of periodic
volume count.
•In volume count, expansion factors are used as follows :29
% time congension = 1000.33%
365
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(a) Hourly expansion factor :
(b) Daily expansion factor
Traffic for a week = DEF HEF Traffic for a particular hour.
(c) Monthly expansion factorTotal traffic for a day
HEF
Traffic for a particular hour

=

 Traffic for a week
DEF
Traffic for a particular day

=

 AADT
MEF
ADT

=

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Q.Itisacommonpracticetodesignahighwaytoaccommodatethetrafficvolume
correspondingto:
a)30
th
hour
b)Peak hour
c)ADT
d)15 min peak period
[IES: 1998]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Basedon30
th
hourlyvolume,forhowmuchpercenttimeduringtheyearcanthe
designerwillinglytoleratetheunfavorableoperatingconditions?
a)30
b)29
c)2.5
d)0.33
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TRAFFIC FLOW & CAPACITY ANALYSIS
a)Traffic Density (k):
•Numberofvehiclesoccupiedbyunitlengthoftheroadiscalledtrafficdensity.
•Itisexpressedasvehicle/km.
•Themaximumvalueof‘k’whicharoadcanaccommodateistermedas‘jam
density’orTrafficdensityunderjamconditionistermedasJamdensity.
•Underjamcondition,thevelocitywillbezero.
•Trafficdensityvarieswithspeedinversely,hencewithincreaseinspeedofa
streamvehiclesonaroadway,theaveragedensityofvehicledecreases.
•Thisisbecausegaporspacingbetweenthevehiclesincreases.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b)SpaceHeadway(S/Hs):Itisthedistancemaintainedbetween2consecutive
vehicletravellinginthesamedirection.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Itisthetotallengthoccupiedbyamovingvehicleonroadwhichincludeslength
ofvehicleandthegapbetweenthetwovehicles.
•ThisgapforsafetypointofviewmustbeequaltoSSDtoavoidthecollision
betweenthetwovehicles,butthisvalueofgapmakesthedesigningoversafe(
Capacityreduces).
•Hence,forgeometricdesignthisgapiscomputedbyneglectedbrakingdistance
andconsideringreactiontimetobe0.7secinstead.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•(***) If “f” is given in question use SSD only.
For geometric design
We make braking distance = 0 and tr= 0.75
l = 6 m.2
D
Makes own S = SSD + l
V
designing over safe S0.278 V tr + l tr = 2.5 sec.
254 f

=+ D
S0.2780.7 V6=+ ( )S0.2Vb VKmph Sm=+→ → ()
( )
()
length of road1 km
Hence Traffic densityK
Space head way S
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NOTE: Under Jam condition, V = 0 kmph
Jam density, l = length of wheel base = 6 m
= 166 veh/km()
( )
1000
K veh/km
Sm
= 1000
K
0.2Vl
=
+ ()
1000
Kj
lm
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(c) Time Headway (Ht):Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Itisthetimegapbetweenpassesoftwoconsecutivevehicles.
•Assumethatastreamofvehicleslowsatcloseintervalonbehindtheother.
•Atverylowspeed,timeheadwayishighandnoofvehiclescrossingasectionon
theroadisalsolow.
•Asthespeedofstreamincreases,thetimeheadwaydecreasesuptoalowestvalue
atacertainspeed.
•Thespeedatwhichthevalueoftimeheadwayislowestrepresentstheoptimum
speedcorrespondingtomaximumflowtermedas“CAPACITYFLOW”.
•Ifspeedoftrafficstreamisfurtherincreasedthemintimeheadwaystarts
increasingresultingindecreaseoftrafficflow.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Hence Traffic volume ()
t t
1 hr3600
q veh/hr
H Hsec
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# Relation between Traffic volume (q), Density (K) and speed (v)
•It is difficult to measure traffic density directly in practical situation, hence the
relationship between volume density and speed is used.
Traffic volume = Traffic density speed.
Also,
From above two equation,( )
(veh/hr)q
Kveh/km
(Km/hr)v
= qKv= S
S(m)1000
(veh/hr)q V
V(Kmph)H
→
=
→ t
3600
q
H
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NOTE:
1) Max value of traffic volume, which a road can accomodateis called traffic
capacity.
2) This traffic capacity under most ideal condition is ternedas BASIC capacity/
Theoretical capacity.
(iv) TRAFFIC FLOW MODELS
•To figure out the exact relationship between the traffic parameters a number of
research is being carried out.
•The result of these researches yielded may mathematical models broadly classified
into followingSt
1000V3600
HH
= S
t
(m) (Kmph)H V
(S)H3.6
→
=
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a) MACROSCOPIC MODEL
(b) MICROSCOPIC MODEL
(a) MACROSCOPICMODEL
•Itrepresentshowthebehaviourofoneparameterstrafficflowchangeswrtanother.
•Followingtypesofmacroscopicmodelsareavailable.
(i) GREENSHIELD’SMODEL
•Green shield assumed a linear speed density relationship to derive this model.
V
f→Free speed @ K = 0
K
j→Jam density @ V = 0
Eqn, y = mx+ C
V = mK+ V
fJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

2 1 f f
2 1 j j
yy0VV
m
xxK0K
−−−
===
−− f
f
j
V
VV
K
−
=+ f
j
This is known as "Gree ShieldsK
VV1
model". very old theory.K
 →
=−

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Now, q = KV
Using the above relation, density can be found at which max flow occurs.f
j
K
qK V1
K

=−

 2
f
f
j
VK
qV K
K
−
= f
f
j
2VKdq
V0
dkK
=−= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Density at which max flow occurs is denoted as j
2K
1
K
= j
K
K
2
= j
oo
K
K Koptimum density
2
== 2
fo
max fo
j
V K
qV K
K
=− 2
j fj fj fj
max f
j
KV KV KV K
qV
24K24
=−== Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Sincefj
max
V K As per Green shield
q
Model.4
→
= 2
f f
j
qVK V K
K
=− q
qKVK
V
== 2
f
f 2
j
V qq
qV
VV K
=− ff
2
j
VV q
1
VV K
=− 2
j fj f
KVVKKVq=− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

To find the speed at which flow is max.
At optimum speed j 2
j
f
K
qK V - V
V

= 

 j
o
K
KK
2
== f
j
K
VV1
K

=−

 j
o
K
VV , K =
2
= of
1
VV1
2

=−

 f
o
V
V
2
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NOTE : In this model linear relationship b/w speed and density is assumed, which is
rarely found in actual, hence several other models are developed to overcome this
drawback.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii) GREENBERG’SLOG-MODEL
•Greenberg used a fluid flow analogy concept and proposed a logarithmic speed
density relationship.
•The greatest advantage of this method is that it can be derived analytically.
•This method shows better fit as compared to green shield model but the drawback
of this model is its inability to predict the speed at lower density as speed
approached infinity at lower density.
•It cannot be used where K is low and speed is high.
As per this model,
Now, q = KVj
oo
j
Vspeed
K
VV lnVoptimum speed
K
KJam density
=

== 


= ( )
j
o o j
K
qK V lnK Vln klnK
K

= = −

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dq
0 maximum
dk
= ( )
o j o
dq 1
VlnKlnKKV
dk K

=−+−

 ()
j
o o o
K
KK Koptimum density
e
=→ jj
max o j
KK
qVln kln
ee

=− 

 ( )
j
o j j
K
Vln klnk1
e
= −+ oj
max max o o
VK
q At q, V = V, K = K
e
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) UNDERWOOD EXPONENTIAL MODEL
•ItisthemodificationofGreenberg’smodelwhichwasunabletorepresentvelocity
ofstreamatlowerdensity.
•Underwoodhenceproposedexponentialmodelfortrafficflowasfollowsf
f
o
o
Vfree mean speen (Kmph)
K
VV e KDensity
K
KOptimum density i-e density
corresponding to max flow
=
−
==
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Underwoodmodeltendstounderestimatespeedatfreeflowphasebut
overestimatethecongestedportion.(Thisisjustoppositeofanalysisingreenberg
model).
•Themaindrawbackofthismodeliswhenspeedbecomezero,densityapproaches
infinity.
•Hence,itcannotbeusedforpredictingspeedathighdensity.
•Howeveritshowsbetterfitthangreenshieldandgreenfieldforuncongested
traffic.
Also,
Foro
K
K
f
qKVK V e
−
== max
dq
q,0
dk
= oo
KK
KK
ff
o
dq 1
K V e Ve
dk K
−−
−
=+ 
 o
K
1
K
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(iv) PIPE’S GENERALIZED MODEL
•In order to generalize the modellingapproach pipe introduced a new
parameter “n”.
•He proposed a model represented by following equation
NOTE: For n=1, This becomes GREENSHIELD MODEL.
Thus by varying “n”, families of model can be developed.n
f
j
K
VV1
K



=− 


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(v) MULTI REGIME MODEL
•All the above models are based on the assumption that the same speed density
relation is valid for the entire range of densities in traffic stream.
•Hence, these models are termed as single regime model.
•However human behaviourwill be different at different densities.
•Hence, speed density relationship will also be different in different zones of
densities.
•Based on this many models were proposed, termed as multi regime models.
Eg: Two regime model.
Zone-I q = KV →const
Relation b/w q and v is linear
Zone-II q = KV
= K (KC)2
KCParabolic=→ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(II) MICROSCOPICMODEL
•Inthesemodeloftrafficflow,analysisofflowoftrafficisdonebymodelling
driveranddrivertoroadinteractionwithinatrafficstreamwhichrespectively
analyzetheinteractionbetweenadriverandanotherdriverontheroad.
#LEVEL OF SERVICE (LOS)Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•LOSisquantitativemeasureusedtorelatethequalityofmotorvehicletraffic
service.
•LOSisusedtoanalyzeroadwaysandintersectionbycategorizingtrafficflowand
assigningqualitylevelsoftrafficbasedonperformancemeasurelikespeed,density,
congestionetc.
NOTE: Here quantitative measure of flow is given by traffic capacity.
•Factors to be considered for the evaluation of a roadway includes
(a)Operating Speed
(b)Travel time
(c)Traffic interruptions
(d)Freedom of movement
(e)Driving comfort
(f)Safety
(g)Economy.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•As per HCM (Highway Capacity manual) following are considered to evaluate
LOS.
(a)Operating speed
(b)Ratio of volume to capacity
•TheHCMandIRCsuggestsixLOS(levelofservices)ofroadwayrangingfromA
toFhavingfollowingproperties.()
c
qq
(i) LOS-A : (ii)LOS B :
•Free flow operation
•No restriction in manuvering
•low traffic
•High speed
•Reasonablyfree flow
•Ability to manuvoredis slightly
restricted.
•Effect of minor incidents still easily
absorbed.
•Stable flow and noticeable traffic.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) LOS-C : (iv) LOS-D :
•Speed is reduced in this case
•Freedom to manuveris noticeably
restricted
•ques may be may formed behind
any significant blockage.
•Significant traffic interaction takes
place.
•Unstable flow condition
•Highdensity
•Movement restriction
•Speed decline significantly.
•Minor incident create queue
NOTE : As per IRC for design of
rural roads LOS-B is adopted and for
design of urban roads LOS-C is
adopted.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(v) LOS-E : (vi) LOS-F :
•Unstable flow.
•lower speed
•volume = capacity.
•very little freedom of movement.
•Any disruption causes of quecing.
•Breakdown in flow.
•Queues from behind breakdown points.
•Here demand > capacity.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# DELAY AND QUEUE ANALYSIS AT SIGNALISED INTERSECTION
For green and Amber both arrival RED →Arrival but no departure
departure are possible Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

1.STOPTIMEDELAY(D):Itisdefinedasthetimeavehicleisstoppedin
queuewhilewaitingtopassthroughsignalizedintersection.
•Itbeginswhenthevehicleisfullystoppedandendswhenthevehiclebeginsto
accelerate
•Averagestoppedtimedelayistheavgforallvehiclesduringthespecifiedtime
period.
•Itismathematicallydifferenceofdeparturetimeandarrivaltime.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

2.QUEUE(Q):Itisthedifferenceoftotalnumberofvehiclearrivalandtotal
numberofvehicledepartureatanyinstantoftime.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE:
Assumptions made in previous analysis:
(i) Vehicles arrive and depart at uniform rate. (Hence cum arrival and departure
curve is linear with time)
(ii) No pre-existing queue is there at intersection.
(iii) Arriving vehicle departs instantaneously when the section light turns green.
(iv) The departure of the vehicles takes place at it max rate termed as
SATURATION FLOW RATE/ SERVICE RATE.
(v) The departure curve catches up with the arrival curve before the next red interval
begins.Area b/w cum. arrival and cum
departure curve for one cycle
time
Here avg. stop time delay =
Cum. no. of vehicle Arrival
per cycle time








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•Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE : Queue length v/s time graph can be converted into cum arrival and
departure v/s time graph.
Case (i) : cum departure matches cum arrival exactly at the end of one cycle.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case(ii)Cumulativedeparturematchescumulativearrivalbeforethecompletionof
cycletime.
•Cumdeparturecurvemeetsarrivalbeforecyclelength.
•Hence,nodelaytimeisthere.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case(iii):Cumulativedeparturedoesn’tmatchescumarrivalevenattheendofone
cycletime.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Thetrafficvolumeofaroadwayisdefinesasthemultiplicationof:
a)Speed and time headway
b)Speed and distance way
c)Traffic density and speed
d)Time head way and distance headway
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Q.Relationshipbetweentrafficspeedanddensityisdescribedusinganegatively
slopedstraightline.If??????
??????isthefree-flowspeedthenthespeedatwhichthe
maximumflowoccursis:
a)??????
??????/4
b)??????
??????/2
c)0
d)??????
??????
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Q.Itwasnotedthatonasectionofroad,thefreespeedwas80kmphandthejam
densitywas70v/km.Themaximumflowinv/hrthatcouldbeexpectedonthisroad
is:
a)800
b)1400
c)2800
d)5600
[IES: 1998]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Onaroadthefreespeedwas65kmphandthespaceheadwayatjamdensitywas
6.25m.Whatisthemaximumflowwhichcouldbeexpectedonthisroad?
a)2600 vph
b)1625 vph
c)1300 vph
d)406 vph
[IES: 2006]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# PROBABILITY OF VEHICLE ARRIVAL
•Arrival of vehicle at a particular section of road is considered to follow “ Poisson’s
distribution”.
•Probability that “N” no of vehicles will arrive within “t” sec time interval.
Case (i) : Probability that vehicle will arrive after time “t”()
()
n
t vehicle arrival rate
te
Pn,t ttime interval or time headway
n!
nno. of vehicle
− =

==
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case (ii) : Probability that vehicle arrive within time “t”
P of vehicles arriving within time t + P of vehicle arriving after time t = 1
P of vehicle arriving within time t = 1 –P of vehicles arriving after time “t”.
(iv) TRAFFIC SPEED STUDIES
•Thespeedofthedifferentvehiclesoveraparticularroutedependsonseveral
factorssuchas
(i) Geometric design of road.
(ii) Driver characteristics
(iii) Climate and environmental factorst
P1e
−
=− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iv) Time of travel
(v) Traffic volume
(vi) Purpose of travel
NOTE:
(1)SpotSpeed:Itistheinstantaneousspeedofavehicleataspecifiedcrosssection
orlocation.
•Thespotspeedofavehiclefluctuatesfromplacetoplaceallalongtheroutes
dependingupontheabovefactors.
(2)AverageSpeed:Itistheaverageofspotspeedofallthevehiclespassingagiven
pointonhighway.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(3)RunningSpeed:Itisaveragespeedmaintainedbyavehicleoveraparticular
stretchofroadwhilethevehicleisinmotion.
Running time = Journey time –Delay
(4) Travel Speed : It is average speed of travel for a vehicle over particular stretch of
road, for entire travel time.
•Traffic speed studies are generally of following typesJourney length
Running speed =
Running time Journey length
Travel speed =
Journey time Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a) SPOT SPEED STUDIES
(b) SPEED AND DELAY STUDIES
(a) SPOT SPEED STUDIES:
•Itisreferredasinstantaneousspeedofthevehicleatapoint/crosssectiononroad.
•Measurementofspotspeedcanbedonebyanyoffollowingmethods.
(i)Bynotingthetimetakenbyvehicletotravelaknowndistanceof15or30m
eithermanuallyormechanicallyorautomatically.
Hence speed is given by v = d/t (m/sec).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii) Spot speed can also be measured with the help of several equipments. like
-Graphic recorder.
-Electronic meter
-Photo electronic meter.
-Photographic meter.
-Radar speed meter.
-Enoscope.
•Spot speed studies are being carried out for following purpose
(i) For planning of traffic regulations.
(ii) Design or redesign of geometric elements.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) In accident studies and preventive measures.
(iv) To find the speed trend over the period of time.
•Dependinguponthemethodofmeasurementofspotspeedi.e,overaparticular
stretchofroadorbyequipmentdifferenttypesofaveragespeedincalculated.
(i) SPACE -MEAN SPEED : It represents the average speed over length at any
time.
•This is obtained from the observed travel time of the vehicles over a stretch of
road.
It is harmonic mean of diff. spot speedS
1 2 3 n
n
V
1111
..
VVVV

=
++++ i
fixed (15-30)md
V
ti
→
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE : The average travel time of all the vehicles is obtained from reciprocal of
space mean speed. S
1 2 n 1 2 n
n dn
V
ttt tt... t
...
ddd
==
++
+++ S
(m/s)dn
V
sec ti
=
→ S
S
i
V or Vspace mean speed
m dlength of roaddn
V3.6 (Km/hr.)
sec nno. of individual veh. observation.ti
tobserved time
=
→=
=
→=
= S
1ti
ta
Vdn

== Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii) TIME MEAN SPEED :
•Itrepresentsthespeeddistributionofvehiclesatapointontheroadwayanditis
averageofinstantspeedofobservedvehiclesataspot.1 2 3 n
t
VVV....V
V Airthmetic mean of spot speed.
n
++++
=→ i
t
m/sV
(m/s)V
n
→
= tt
ii
t
V , VTime mean speed.
(m/s) Vobserved inst. speed of ith vehicle. V
(Kmph)V3.6
nno. of vehicle observed.n
→
→=
=
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# Presentation of spot speed data
It can be done by following.
(i) Speed distribution Table
•From spot speed data Frequency distribution table of spot speed can be prepared,
by arranging the speed groups covering desired speed range and the number of
vehicles in each speed range.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Speed range (Kmph) No. of vehicle
observed/frequency
% Frequency
0 –10
10 –20
20 –30
30 –40
40 –50
50 –60
60 –70
70 –80
80 –90
2
5
10
15
30
55
200 →max m
63
40
1.25
2.5
3.75
7.5
13.75
50
1.75
5
4002
1000.5
400
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii) Frequency distribution curve:
•A graph is plotted with the average values of each speed group of vehicles on the
x-axis and the % of vehicles in that group on y-axis.
•This curve is termed as Frequency distribution curve.
•This curve has a definite peak of travel speed across the section and this speed is
denoted as “model speed”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) Cum. Freq. distribution curve:
•It is the curve plotted with avg values of each speed group on x-axis
•With the help of this curve following significant speed are noted.
(a)98
th
Percentile speed:
•Itisthespeedatorbelowwhich98%ofthevehiclesaremovingandonly2%
vehiclesexceedsthislimit.
•AsperIRC,thisspeedisconsideredasdesignspeedforGeometricelements.
(b) 85
th
Percentile speed:
•Itisthespeedatorbelowwhich85%vehiclesaremovingandonly15%of
vehiclesexceedsthislimit.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thevehiclesexceedingthislimitareconsideredtobedrivingfasterthansafe
speed.
•Henceitisconsideredasuppersafelimit.
(c) 15
th
Percentile speed:
•Forthepurposeofavoidingcongestion/Jamoveraparticularroadthisspeedis
determinedasitisconsideredaslowersafelimit.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iv)SPEED DISPERSION:
•Thespeeddistributionofvehiclesgenerallyfollownormaldistributioncurve.
•Theamountofspreadofspeedfromavgspeedistermedasdispersion,whichcan
bereportedintermsoffollowing.
(a) 85
th
–15
th
percentile speed.
(b) Standard deviation of spot speed.
(c) Coeffof variation of spot speed.
(b) SPEED AND DELAY STUDIES:
•Thisstudygivestheideaofrunningspeedorthefluctuationsinspeed,the
locationanddurationofdelaysorstoppageandtheoveralltravelspeedb/wtwo
desiredlocationalongtheroad.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Theresultofthisstudycanfurtherbeusedinidentifyingthelocationof
congestion,causesofdelayhencehelpsinimprovementofexistingroadorin
designofnewroad.
•Thedelayisfurtherclassifiedintotwo.
(a)Fixeddelay:Theseoccurparticularlyatintersectionduetotrafficsignals.
(b)Operationaldelay:Theseoccursduetointerferenceoftrafficmovementssuch
asturningofvehicles,parkingandun-parkingofvehiclesorpedestrainetc.
•These studies are being carried out by several methods:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a) FLOATING CAR OR RIDING CHECK METHOD:
NOTE : This method is applicable for two lane two way road.
•Inthefloatingcarmethod,atestvehicleisdrivenoveragivenroutetotravelat
approxtheaveragespeedofthestream,thustryingto“FLOAT”withthetraffic
stream.
•Theno.oftestrunaremadealongthestudystretch.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Agroupof4–observerareseatedinthetestvehicletorecordvariousobservation
duringthetestineachrunasfollows:
OBSERVER1:Itisprovidedwithtwostopwatchesfromwhich.
ONEisusedtorecordthetotaljourneytime
OTHERisusedtorecordthedelaytimeatdifferentlocations.
OBSERVER2:Itnotesthetime,locationandcauseofthedelaysduringeachtest
run
OBSERVER3:Itnotesno.ofvehiclesovertakingthetestvehicleandnoof
vehiclesovertakenbytestvehicle.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

OBSERVER 4 : It notes the number of vehicles travelling in the opposite direction
in each test run.
According to this method following results are obtained
tw= avgjourney time of test vehicle when running / moving with the flow.
ta= avgjourney time of test vehicle when running against the flow.a
Traffic flow : q
twta

+
=
+ y
Journey time of flow : ttw
q

=− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.


a= avgno. of vehicles on study (L km) in the direction of flow.can be avg no. of vehiclesavg no. of vehi cles
ve , -ve overtaking the testovertaken by
or even zero vehicle test vehicle



+ = −


 This data is recorded by 4th observer while
traveling in opposite direction.


 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b) LICENCE PLATE METHOD:
•Inthismethod,observersarestationedattheentranceandentryoftheteststretch.
Wheretheinformationoftraveltimeisrequired.
•Thetimingofvehicleenteringandleavingtheteststretchisnotedtocomputethe
vehiclespeed
(c)INTERVIEWTECHNIQUE:
•Interviewofrider.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(d) ELEVATED OBSERVATION AND PHOTOGRAPHIC TECHNIQUE :
# ORIGIN AND DESTINATION STUDIES
•OandDstudiesgivestheinformationontheactuallocationorzoneoforiginof
travelofvehiclesandtheirdestinations.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thesestudiesprovidedetailssuchasdirectionoftravelsectionofrouter,trip
length,frequencyandnumberofsuchtripandno.ofindividualstravellingin
particulartrip.
•Thesestudiesfindtheirapplicationin.
(a) To judge the adequacy of existing routes.
(b) To establish design standards.
(c) To locate expressway and major roads.
(d) To locate new bridge as per traffic demand.
(e) To identity potential congestion points.
•O and D studies can be carried out by any of the following methods:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a)RoadSideInterviewMethod:interviewattheroad.Congestion,wrong
information.
(b)LicensePlateMethod:sameas
(c)ReturnPostCardMethod:questionswillbepresentinpostcard.Inaccurate
information.
(d)TagonCardMethod:Fastag,originanddestinationcanbeanalysed.Costly.
(e)HomeInterviewMethod:interviewsathome.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Originanddestinationstudiescanbepresentinanyoffollowingforms.
(a)OandDTables:arepreparedshowingno.oftripsb/wdifferentzones.
(b)Desireline:ThisareplottedwhichisagraphicalrepresentationpreparedinO
andDstudies.
•Thesearest.linesconnectingtheoriginpointswithdestination.
•Thewidthofsuchdesirelineisdrawnpropotionaltonumberoftripsinboth
directions.
•Thedesirelinedensitymaphelpstodecidetheactualdesireoftheroaduserwrt
thepathtobefollowedb/wtwopoints.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(c) O and D studies data can also be represented in the bottom of “PIE chart” and
“contour lines”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Anobservertravellingataconstantspeedof70kmphwiththetrafficstreamover
5kmstretchispassedby17vehiclesmorethanwhathepasses.Whentheobserver
travelsagainstthestreamatthesamespeed,thenumbervehicleshemeetsis303.
theflowofthetrafficstreamis:
a)4480 vph
b)4160 vph
c)2240 vph
d)2002 vph
[IES: 2001]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Whichsetoftrafficstudiesisneededforfunctionaldesignaswellasfor
‘highwaycapacity’design?
a)Origin and destination studies
b)Parking and accident studies
c)Speed and volume studies
d)Axle load studies
[IES: 2009]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Thedurationofgreentimeinatrafficsignaldependson:
a)Traffic density
b)Traffic volume
c)Traffic speed
d)All of the above
[IES: 2015]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vi)PARKINGSTUDIES:
•Allthevehiclesdonotkeepmovingalongtheroadwayduringtheentire24hrsof
day,theyhavetostoporparkatdesiredlocationfordifferentdurations,Hence
parkingstudiesarebeingcarriedouttoCatertheneedofparking.
•Parkingfacilitiesmaybebroadlydividedintotwotypes.
(a) OFF street parking
(b) ON street parking / KERB parking
(a)OFFSTREETParking:Atlocationswhereparkingdemandisveryhighand
kerbparkingcannotbepermittedinviewoftrafficcongestion,offstreetparking
isprovided,dependinguponavailabilityofspace.
•Inthistypeofparkingvehiclesarenotallowedtostandinkerbbutsomedistance
isfromit.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thesearefurtherclassifiedintotwo
(1)SurfaceParking (2)MultiFloorParkingGarage
(b)ONSTREETParking:Inthistypevehiclesareparkedalongthekerb,which
maybedesignedforparking.
•Inisconvinientforthosewhocouldfindasuitablespacetoparkthevehicleat
desiredlocation.
•Differentpatternsofkerbparkingare:
(1)ParallelParking (2)AngleParking
(1)ParallelParking:
•Itrequireslesssroadwidthbutthenumberofvehiclesthatcanbeparkedper
unitlengthofroadisleastinthiscase.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Itispreferredwhenthewidthofkerbparkingspaceandwidthofstreetsare
limited.
•Inthiscaseparkingandunparkingaremoredifficultandtimetaking.
(2)AngleParking:
•Inthiscasevehiclesarebeingparkedatananglerangingfrom30
o
,45
o
,60
o
and
90
o
.Llength of the KerbL
N
NNo. of parking spaces6.6
=
=
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thewidthofroadwayrequiredforparkingandunparkingincreasesinthiscase
withincreaseinangleandbecomesmaxat90
o
.
•Itcanaccommodatemorevehiclesperunitlengthofkerb,withmaxnoofvehicles
beingparkedat90
o
.
•Thistypeofparkingisconvinent,butcreatesmoreobstructiontothetraffic.
•Outofvariousanglesforparking,45
o
angleparkingisconsideredtobebest
accountingalltheparameters.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vii) ACCIDENT STUDIES:
•Theproblemofaccidentsisverysignificantduetocomplexflowpatternsand
presenceofmixedtypeofvehicleovertheroadway.
•Theseaccidentsmayinvolvepropertydamage,personalinjuriesandmayeven
deathalso.
•Theaccidentstudiesarebeingcarriedoutforfollowingobjectives.
(a)Tostudythecauseofaccident.
(b)Toevaluateexistingdesignandcontrolmeasures
(c)Toevaluatethetotallossduetoaccidents.
(d)Toanalysethechangesrequiredinexistingdesign.
•Theaccidentsmaybecausedduetoanyoneormoreofthereasons:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a) Drivers negligence (d) vehicle defect
(b) Pedestrian (e) Road condition
(c) Passengers (f) Road design
(h) Weather (Fog,rain) (g) Traffic condition
•Accident data can be reported in any of the following forms.
(a)LOCATIONFILES:Inthisfiles,locationoftheaccidentisbeingmarkedwhich
isfurtherusedtoidentitythelocationsofhighaccidentrate.
(b)SPOTMAPS:Thismapsshowsaccidentbyspotspinsorsymbolsontheroad
mapofthelocality.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The common symbol used are.
•Type of accident FATAL NON-FATAL
Motor vehicle-pedestrain
other motor vehicle Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(c)Collisiondiagram:Thisdiagramdepicttheaccidentlocationandshowthe
approxpathofvehiclesandpedestriansinvolvedinaccidentandalsootherobjects
•Analysisofindividualtrafficaccidentscanbedoneonthebasisoffollowing
assumptions.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a)Whenskidmarksarepresenttheskiddistancearemeasuredtofindactual
brakingdistanceandisassumed100%skidhasoccurredduetobraking.
(b)
As per momentum conservation.
Total momentum before impact = Total momentum after collision. AB
11
BA
vel. of approach = VV
vel. of separation = VV
−
− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE:Herevel.ofseperationcanbelinkedwithvel.ofapproachwiththehelpof
coefficientofrestitution.
Forelasticcollision,e=1
(c)Theimpactofvehiclemaybedirect/obliqueatknownangle.
(d)Coeff.offriction(t)ofpavementsurfaceundertheexistingconditionmayeither
bedeterminefrombraketestorisassumed.''
AA BB AA BB
MVMVMVMV+=+ ''
BA
AB
VVvelo. of separation
c
velo. of approachVV
−
==
− ''
B A A B
VVVVvel. of sep = vel. of approach.−=− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Analysis of initial speed from skid distance is done as follows.
KE = work done.
•If the vehicle stops after skidding the distance “S”
Hence, V
2= 022
21
11
m Vm VFrictiondistance
22
−=− ( )
22
12
m
VVf mg S
2
−=− 2
12
VV2fgs=+ 1
V2fgs= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

ACCIDENTTYPE 1 : Collision of moving vehicle with parked vehicle.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Step 1 : Before collision
KE = WD
Properties VehAVehB
(i)InitialSpeed V
1 0
(ii)Speed just before collision V
2 0
(iii)Speed just after collision V
3 V
3
(iv)Skid before collision S
1 0
(v)Skid after collision S
2 S
2
(vi)Mass Ma Mb22
2 1 1
11
m Vm Vfmags
22

− =−

 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Step 2 : At collision
Momentum before collision = Momentum after collision
From (1) and (2)22
1 2 1
VV2fgs - (1)=+ A2 B A3 B3
mVmomVmV+=+ ( )
AB
23
A
mm
V V - (2)
m
+
= 2
22 AB
1 3 1
A
mm
V V2fgs - (3)
m
+
=+
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Step 3 : After collision
KE = WD
From equation (3) and (4)( ) ( ) ( )
22
A B A B3 A B 2
11
mmommVmmgfs
22
+−+=−+ 2
32
V2gfs - (4)= ( )
2
2 aB
1 2 1
A
mm
V 2gfs2gfs
m
+
=+
 2
AB
1 2 1
A
mm
V ss2gf
m

+
=+


 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Considerthefollowingstatements:
Collisiondiagramisusedto
a)Studyaccidentpattern
b)Eliminateaccidents
c)Determineremedialmeasures
d)Makestatisticalanalysisofaccidents
[IES: 1996]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# TRAFFIC CONTROL DEVICES AND REGULATION
(i) INTERSECTION:
•Anintersectioniswheretwoormoreroadsjoinsorcross.
•Attheintersection,therearethrough,turningandcrossingtrafficmovements.
•Thismovementsoftrafficarehandleddependinguponthetypeofintersection.
•Intersectionsarebroadlyclassifiedintotwo.
(a)INTERSECTIONAT GRADE
•Whenalltheroadsmeetsataboutthesamelevelallowingthetrafficmovements
likecrossing,weaving,merginganddivergingarecalledintersectionatgrade.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thebasicrequirementsofintersectionatgradeare
(a)Attheintersectiontheareaofconflictshouldbeminimum
(b)Therelativespeedofvehicleandangleofapproachshouldbeminimum
(c)Adequatevisibilityshouldbeavailableforallthevehicles.
(d)Sufficientlightingatnightisdesired.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(e) Proper sign should be installed
(a)Thepointwherethepossiblepathoftwovehiclesintersectiscalled“conflict
point”
The area containing all possible conflict points is termed as “conflict area”.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Iftherelativespeedandangleofapproachoftwovehiclesismoreitincreasesthe
possibilityofcollisionb/wthevehiclesandtheseconflictpointaretermedas
majorconflictpoints.
Eg:Crossingandweavingconflict.
•IfRel.velocityandandofapproachoftwovehiclesisless,possibilityofcollision
decreasesandthesearetermedasminorconflictpoints.
Eg:MergingandDivergingconflict.
•IRCdo-notconsiderdivergingconflict.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case(1):Conflictoncrossroadswithtwowaytrafficonbothroads.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case (2) : Conflict on cross roads with one-ray regulation on one road.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Case (3) : Conflicts on cross roads with one way regulation on roads.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Conflict Area
NOTE : Number of conflict point for diff road comb. Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•At grade intersections are further of following types.
Number of lanes Number of potential conflicts
Road 1 Road 2 Both road
two way
1 : One way
2 : Twoway
Both road
one way
2 2 24 11 6
2 4 32 17 10
4 4 44 25 18Ma:16
Mi:8


 Ma7
Mi4
=

=
 Ma4
Mi2
=

=
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a) UNCHANELISEDINTERSECTION:
•Inthisentireintersectionispavedandthereisnorestrictiontothevehiclestouse
anypartofthisintersectionarea.
•Itisveryeasytoconstructbuthasmostcomplextrafficoperationsoverit
resultinginlargeconflictarea.
•Itissuitabletobeprovidedwheretrafficvolumeislow.
(b) CHANNELISEDINTERSECTION:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Itisachievedbyintroducingislandsintotheintersectingorintersectionareain
ordertochannelizethetrafficflowintodifferentstreams.
•Itreducesthetotalconflictareaavailable.
•Itdoesnotreduceconflictpoints.
•Itiscomparativelydifftoconstruct.
•Channelizingislandsprovidedinthiscaseservesthefollowingpurpose.
(a)Reducesrelativespeed
(b)Reducesrelativeangle
(c)Reducesconflictarea
(c)ROTARYINTERSECTION:
ItisanenlargedroadintersectionwherealltheconvergingvehiclesareforcedtoJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

movearoundalargecentralislandinonedirectionbeforetheycanweaveoutof
trafficflowintotheirrespectivedirectionradiatingfromcentralisland.
•Themainobjectiveofprovidingarotaryistoeliminatetheneedofstoppingover
forcrossingstreamsofvehicleandtoreducetheareaofconflicts.
•Byprovidingrotarycrossingconflictiseliminatedandconvertedintoweaving
conflictwhichconsistoffollowing.
(i)Mergingmaneuver(movement)fromtheleftanddivergingouttotheright.
(Blackline)
(ii)Mergingfromrightandadivergingouttotheleft(Greenline).Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Design factors for rotary intersection :
(a)DESIGNSPEED:Vehiclesapproachingatgradeintersectionhaveto
considerablyslowdowntheirspeedascomparedtodesignspeedofthatparticular
road,howeverthereisnoneedforvehiclestostopsatrotary.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•For rural areas design speed = 40 Kmph.
urban areas design speed = 30 Kmph.
NOTE:SinceinIndiawefollows“Keeptoleft”notations,flowofvehiclearound
centralislandisinclockwisedirection.
(b) SHAPE OF ISLAND:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Theshapeofcentralislanddependsonthenumberandlayoutofintersecting
roads.
•Whentwoequallyimp.Roadscrossatroughlyrightanglesi.e.allthefour
radiatingroadsareplacedsymmetrically,circularshapeissuitable.
•Theislandmaybeelongatedtoaccommodateinlayoutwheremorethanfour
intersectingroadsaretheretermedonellipticalshape.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•“TANGENTSHAPE”isnotdesirableasthereistendencyoftrafficinthis
directiontomovemuchfasterthenspecifiedspeed.
•“TURBINESHAPE”forcesreductioninspeedofvehicleenteringtherotary,but
createstheproblemduetoheadlightglare.
(c)RADIUSOFCENTRALISLANDANDROTARY:
Asincaseofnormalhorizontalcurve,centrifugalforceisresistedbyfrictionand
super-elevation.
Similarlyincaseofrotaryroadwaysitisresistedonlybyfrictionassuper-elevation
cannotbeprovidedinthiscase22
vv
ef f =
127 R127 R
+= 2
Kmphv
R
127f
→
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Hence, radius of entry curve is as follows.
•IRC recommends min. radius of central island to be 1.33 times of radius of entry
curve.
•Vehicles leaving the rotary would accelerate to the speed of radiating road and
hence the exit curve should be of larger radius than entry curve.
•IRC recommends radius of exit to be (1.5 –2) timer the radius of entry curve.
Type of Road Design speedv
(Kmph)
Radius (m)
Rural 40 20 –35
Urban 30 15 -25Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(d)WEAVINGAREA:Sincebyprovidingrotarycrossingconflictisconvertedto
weavingmovement,whichtakesplaceinzonetermedasweavingarea.Henceits
designbecomessignificant
•Forsmoothtrafficflow,theweavingangleshouldbesmallbutnotlessthan15
o
as
itwouldincreasediameterofcentralisland.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•The weaving length should be at least four times the width of weaving section.
•The recommended value of weaving length is (45 –90)m for design speed of 40
Kmphand (20 –60)m for 30 Kmph.W
W
Maximum weaving angle
BWeaving width
=
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(e) WIDTH OF CARRIAGEWAY :
•AsperIRCwidthatentryandexitfordifferentlanesofapproachroadareas
follows:Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(f) WIDTH OF ROTARY ROADWAY :
•Thewidthofnon-weavingsection(e
2)oftherotaryshouldbeequaltowidest
singleentrytotherotaryandshouldgenerallybelessthanthewidthofweaving
section(e
2<B
W)
Road (Rural) Roads (Urban)
No. of lanes2 3 4 62 3 4 6
Width of
carriageway at
entry and exit
(m) (e
1)
6.5 7 8 137 7.510 15Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Thewidthofweavingsection(B
W)oftherotaryshouldbeonetrafficlanewider
thanthemeanwidthoftheentryandnonweavingsection.12
W
ee
i.e. B 3.5e3.5
2
+
=+=+
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# CAPACITYOF ROTARY :
Thepracticalcapacityofrotaryisdependentuponmincapacityoftheindividual
weavingsectionandisgivenbyfollowingexpression.
Q
P=practicalcapacityofweavingsectionofrotary(PCU/hr)
B
W=widthofweavingsection(6–18)m
e=Averagewidthofentry(e
1)andwidthofnon-weavingsectione
2W
W
P
W
W
eP
280 B11
B3
Q
B
1
L
 
+− 

=

+
 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE : Here12
ee
e
2
+
= W
e
0.41
B

=−
 ppropotion of weaving traffic
bfc
b = p = (0.4 - 1.0)
abcd
=
+++ aRight turning traffic from extreme left lane.
Not participating in weaving
b = Right turning traffic from extreme right lane.
bweaving traffic turning towards right
Participate in weaving
=


= while entering the rotary.
c = weaving traffic turning left while leaving the rotary


 Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•As per IRC, the following PCU values for diff. types of vehicles are as follows:
PCU
(i) Car, LCV, Three wheeler = 1
(ii) Buses, MCV = 2.8
(iii) Motor cycle, scooter= 0.75
(iv) Pedal cycle = 0.5
(v) Animal drawn vehicle = 4 –6
(g) CHANNELIZINGISLAND:
These are provided at the entry and exit of the rotary for the following purpose.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(i) To reduce the conflict area
(ii) To force the vehicles to reduce their speed
(iii) To provide space for erecting traffic signs.
(iv) To improve the aesthetic.
•The islands are provided with kerbsof 150 –200 mm high.
(d) SIGNALISEDINTERSECTION:
•Intersectionatgradethatarecontrolledbytrafficsignalsarecalledsignalized
intersection.
•Theautomatictrafficcontrolsignalsareoperatedtoalternatelystopandletgothe
trafficenteringtheintersectionfromtheapproachless,thuspreventingthe
conflicts.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b) GRADE SEPARATED INTERSECTION
•It is the highest form of intersection available
•Grade separation is achieved by means of vertical level separation of intersecting
roads by means of providing
(i) An over bridge (fly over)
(ii) By underpassJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Flyover
•No drainage problem
•Lateral expansion is easier
•Vertical profile will be totally
disturbed.
•Construction cost is less
•Limit heavy vehicle
Underpass
•Drainage Problem
•Expansion is diff.
•Not aesthetic
•Cost is less than overpassJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Interchanges can also be classified on the basis ofshape as follows.
(a) DIAMOND (c) Partial clover leaf
(b) Rotary (d) Full cover leaf
DIAMOND INTERCHANGE ROTARY INTERCHANGE Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

PARTIAL CLOVER LEAF FULL CLOVER LEAF
. Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Considerthefollowingparametersrelatedtoarotaryintersection:
1.Width of the weaving section.
2.Length of the weaving section.
3.Proportion of weaving traffic.
4.Weaving angle.
5.Width of the carriageway at entry.
Capacity is generally expressed in terms of
a)1, 2, 3 and 4
b)1, 2, 3 and 5
c)1, 2 and 3
d)4 and 5
[IES: 1997]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Whichoneofthefollowingisthepurposeofdivisionalisland?
a)To divert the traffic into definite travel path at the intersection.
b)To reduce the speed of traffic entering the intersection.
c)To divert traffic from obstacles and expenditethe flow of traffic.
d)To segregate opposing flow of traffic in a multi-lane highway
[IES: 2001]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Considerthefollowingstatementsrelatedtointerchanges:
1.In diamond interchange there is the possibility of illegal wrong way turns.
2.Diamond interchange is far superior to cloverleaf design.
Which of the statements given above is/are correct ?
a)1 only
b)2 only
c)Both 1 and 2
d)Neither 1 nor 2
[IES: 2007]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Whichoneofthefollowinggeometricfeaturesrequiresthemagnitudesof
weavingangleandweavingdistanceforitsdesign?
Rotarydesign
Rightangleintersection
Roundabout
Grade-separatedjunction
[IES: 2009]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# (E) TRAFFIC CONTROL DEVICES
•Thedevicesplaceinordertocontrolthetrafficflowistermedastrafficcontrol
devices.
Eg: Traffic signals, signs, pavement marking etc
These devices are classified as follows:
(i) Regulatorydevices:
•Thesegivestheroadusernoticeoftrafficlawsorregulationsthatapplytogiven
•Disregardofsuchdevicesispunishableasanviolation.Eg.STOP,Noturning,No
parkingetc.
(ii) Warningdevices:
•These call attention of the road user to the condition on the roadway, that are
potentially hazardous to traffic operation.
Eg: Narrow road ahead, slippery road etc. Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(iii) Guiding/ Informatory:
•Theseprovidedirectionsandinformationtotheroaduserregardingdistances,
destinations
(I) TRAFFICSIGNAL:
•Thesearecontroldeviceswhichcouldalternatelydirectthetraffictostopand
proceedatintersectionusingredandgreentrafficlightsignals.
•Themainrequirementoftrafficsignalsare:
(a)Itshoulddrawtheattentionofroaduser.
(b)Itshouldprovidetimetorespond.
(c)Itshouldhaveminimumwasteoftime.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Traffic signals are of following types:
(1) TRAFFIC CONTROL SIGNALS:
•Thesesignalsareprovidedtocontrolthetrafficattheintersectionandhavethree
colouredlight,facingeachdirectionoftrafficflow
•Thesearefurtherclassifiedintothree.
(i)Fixedtime/Pretimed:Thesearesaidtorepeatregularlyacycleofred,amber
andgreenlights.Thetimingofeachphaseispre-determined.
•Themaindrawbackofthesesignalsisthatsometimestrafficflowononeroad
maybealmostnilandtrafficoncross-roadmaybequiteheavybuttimeavailable
inbothcasesissame.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ii)Semi-actuated:Thesearesignalswhosetimingisaffectedwhenvehiclesare
detectedbyvideosensorsonsomebutnotalltheapproaches.
(iii)Fullyactuatedsignals:Thesearethesignalstimingsofwhichiscompletely
influencedbythetrafficvolumewhendetectedonalltheapproaches.
(2)PEDESTRAINSIGNALS:Thesesignalsareprovidedtocontrolthemovement
ofpedestrianalongtheapproachestointersection.
(3)SPECIALTRAFFICSIGNALS:Thesesignalsareprovidedtoawaretheroad
userabouttheconditionprevailedaheadonroadway
Eg: BEACONJaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

# ANALYSIS OF TRAFFIC AT SIGNALISED INTERSECTION
(i) CYCLE: A signal cycle is one complete rotation of all the indications provided.
(RED, AMBER, GREEN).
(ii) CYCLELENGTH: It is the time in seconds that it takes a signal to complete
one full cycle of indications i.etime interval between starting of green for one
approach till the next time the green appears.
(iii) INTERVAL: It represents change from one stage to other. These are of two
types.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a)CHANGEINTERVAL:Itrepresentsyellow/ambertime.
•Itindicatestheintervalb/wgreenandredsignal.
(b)CLEARANCEINTERVAL:Itrepresentsallredtime.Itisincludedaftereach
yellowintervalindicatingaperiodduringwhichallsignalphaseshowredandis
usedforclearingtheintersection.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Hence,
or
•Thus cycle time is ALL RED time or sum of ALL GREEN and ALL AMBER. A A A A A B
B B B B B A
CGAR - (i) GAR - (iii)
or
C = GAR - (ii) GAR
=++ +=
++ += BA
CRRAll re 1=+→ ( )( )
( )( )
A A B B
A B A B
CGAGA
GGAA
All green All Amber
=+++
=+++ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

NOTE:clearancetime/intervalisprovidedafteryellowintervalandisoptional.
Henceifintersectionissmallthenthereisnoneedofclearanceinterval.
(iv)GREENTIME/INTERVAL(Gi):Itisprovidedtoallowtrafficflowthroughthe
intersection.Itisdesignedonthebasisoftrafficvolumeofgivenroad.
•Itisactualtimeforwhichgreensignalistunedon.
(v)REDTIME/INTERVAL:Itisprovidedtostopthetrafficflowonthe
intersection.
•It is designed on the basis of cross road traffic volume
•It is the actual duration the red light is turned on.
(vi)AMBERTIME:Itistheclearancetimeprovidedafterthegreentime,justfor
clearanceoftraffic,sothattrafficonthecross-roadcanbestarted.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(vii)PHASE:Thephaseisdefinedasthesumofdisplayedgreen,yellow,redtimes
foramovementorcombinationofmovementthatreceivetheRIGHTOFWAY
simultaneouslyduringthecycle
•Thesumofphaselengthisthecyclelength.
•Inthetrafficmovementatintersectionfollowingtypeofphasesmaybeobserved.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(viii)LOSSTIME(t
L):Duetotrafficsignal,trafficstreamsarecontinuouslystartedandstoppedhence
everytimethishappensaportionofcyclelengthaslosstimei.etimewhichisnotservingtothetraffic
movement.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

•Total loss time is combination of
(a)Startuplosstime(t
SL):Itoccurswhenasignalindicationturnsgreenfromred.
Driversinthequeuedonotinstantlystartmovingandthereisaninitiallosdueto
reactiontothechangeofsignalindication.
•Thisstartupdelayresultsinaportionofgreentimenotutilised.SL 1 2 3 n
n
SL i
i1
teee........e
te
=
=++++
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

i= phase number.
•Asthesignalisinitiated,thetimeintervalb/wthetwovehiclesreferredas
headwayisnoted.
•Thefirstheadwayisthetimeintervalb/wtheinitiationofgreensignalandthe
instantvehiclecrossesthekerbline.
•Successiveheadwaysarenownotedandareobservedtobecomparativelylower,
becausetheseconddrivercanoverlaphisreactiontimewiththatoffistdriver.t
SLis
generally2sec
•Afterfewvehiclestheheadwaywillbecomeconstant.( )
i
3600
Saturation flow rate of intersection (S) veh/hr
h
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(b)Clearancelosstime(t
cl):Whenthesignalturnsyellowaportionoftimeduring
yellowintervalisnotutilizedbythetrafficgenerally.
•Additionallyifthereisallredinterval,thistimeperiodisalsogenerallynot
utilizedbythetraffic.
•Thisperiodoftimeduringthechangeandclearanceintervalthatarenot
effectivelyutilizedistermedasclearancelosstime.
Hence, L SL CL
Ttt=+ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(ix)EFFECTIVEGREENTIME:Duetotheabovelosstime,timeavailableforthe
movementofvehicleinactualisreducedtocrosstheintersectionandistermedas
“effectivegreentime”.L
Effective gree timegiGiTTotal hrs

Total green time
=−→
 ( )
SL a
giGiAitt=+−+ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(x) CAPACITY: if C = cycle length (sec)
•Effective green time of each cycle = gi
•Total eff. Green time
•If time headway b/w the vehicles is “h” sec
•Total number of vehicles crossing the intersection in hr. ( )
3600
No. of cycle in hrs = cycle/hr
c 3600
= gi
c 36001
= gi
ch
 ( )
3600 gi
capacity of lane = veh/hr
ch Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(xi) CRITICALLANE VOLUME :
•Duringanygreensignalphase,severallaneononeormoreapproachesare
permittedtomove
•Oneofthesewillhavemoretrafficvolumethentheotherandwillrequiremore
time,thananyotherlanemovingatsametime.
•Ifsufficienttimeisallocatedforthislane,thenalltheotherlaneswillalsobe
accommodated.Thevolumeofthislaneistermedas“CRITICALLANE
VOLUME”.i
capacity of lane = Sgreen ratio 3600
Si Saturation flow rate
h
== gi
green ratio
c
= Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Determination of cycle length on the basis of startup loss time
NOTE : If saturation flow for diff phase is different()
SL
c
n t
cycle timeC = sec
V
1
S

− sl
c
tstartup loss time in each phase
n = number of phase
Vcritical volume
S = saturation volume
c = cycle time
=
= th
ciSL
th
ci
Vcirtical vol. for i phasen t
c
V SiSaturation vol. for i phase
1
Si
=
=
=
− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Eg:ci
1 2 3 4
V120010004001600
SiSSSS
=+++ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

SIGNALDESIGN
Designingofsignalcanbedoneasfollowed:
(a)WEBSTERMETHOD:
Inthismethodoptimumcycletimeiscomputedfromleasttotaldelayatsignalized
intersection.
Optimumcycletime,()
o
1.5 L + 5
C sec
1Y
=
− Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Y = less than 1
NOTE : This method is empirical in nature.
Now green time is given by(veh/hr)3600
Si
time headway (sec)h
→
=
→ 1 SL CL
1 2 n
1 2 n
1 2 n
1 2 n
th
i
i
lnLRLoss time
n = no. of phases
ttotal loss time = tt(2sec)
RAll Red time
y = yy........y
q q q
y, y, ......y
S S S
qcritical lane volume for i phase
SSaturation capacity for i
=++=
= +=
=
+++
= = =
=
=
th
phase. ( )
o1
1
1 2 n
CLy
G
yy......y
−
=
++ ( )
o2
2
1 2 n
CLy
G
yy......y
−
=
++ Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(II) ROADMARKING:
•Markingonthecarriagewayandontheobjectswithinandadjacenttotheroad
wayareusedasameansofguidingandcontrollingthetraffic
•Theypromoteroadsafetyandensuresmoothflowoftrafficintotherequiredpath.
•Carriagewaymarkingareoffollowingtypes.
(a)Abrokenlongitudinallineisusedforindicatingthecentrelineontwoorthree
laneroadsandforlanemarkingonmultilaneroads.
•Driversmaycrosstheseattheirdiscretion,iftrafficpermits
(b)Longitudinalsolidslinesareusedasguidingorregulatinglinesandarenot
meanttobecrossedbythedriver,exceptforentryorexitfromapremisesora
sideroadortoavoidastationaryobject.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(c)Doublesolidlineindicatesmaximumrestrictionandarenottobecrossedexcept
inemergency.
(d)Inacombinationofbrokenandsolidlines,asolidlinemaybecrossedwith
discretionofthedrivercloser/nearertoit.Butsolidlinecannotbecrossed.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(III) ROADDELINEATORS:
•The purpose of delineator is to provide visual assistance to driver about the
alignment of the road ahead especially at the night.
•Reflectors are used on delineators for better night visibility.
•These are further classified as :Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(a)Roadwayindicator:Thisareintendedtodelineatetheedgesoftheroadwayso
astoguidealignmentoftheroadahead.
(b)Hazardmarker:Thisaretodefineobstruction,likeguard-rails,abutments,
culvertetcwhicharenarrowerthanroadwaywidthatapproaches.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

(c)Objectmarker:Theseareusedtoindicatethehazardandobstructionwithinthe
vehicleflowpathEg:channelizingislands.Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q. In a three-phase signal system design for a four-leg intersection, the critical flow
ratios for each phase are 0.18, 0.32, and 0.22. The total loss time in each of the
phases is 2s. As per Webster’s formula, the optimal cycle length (ins, round off to
the nearest integer) is -----
[GATE: 2021]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Thenormalflowsontwoapproachroadsatanintersectionarerespectively500
pcu/hand300pcu/h,thecorrespondingsaturationfloware1600pcu/honeachroad.
Thetotallosttimepersignalcycleis16s,thentheoptimumcycletimebywebster’s
methodis
a)72.5 s
b)58 s
c)48 s
d)19.3 s
[IES: 2018]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

Q.Thelosttimeduetostartingdelayonatrafficsignalapproachisnotedtobe3
seconds,theactualgreentimeis25secondsandambertimeis3seconds.How
muchistheeffectivegreentime?
a)19 sec
b)25 sec
c)27 sec
d)31 sec
[IES: 2004]Jaspal Sir Use code "JASPALLIVE" for instant maximum discount on Unacademy Plus subscriptions.

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