CE 368 Highway Engineering Lecture 1.ppt

Engineering

1. CE 368 HIGHWAY
ENGINEERING
Lecture 1
Dr. M. Salifu
Department of Civil Engineering
KNUST
Lecture 1 on 01/02/07 1

2. Lecture 1 on 01/02/07 2
OUTLINE OF COURSE
•PRINCIPLES OF HIGHWAY LOCATION
–Conventional Ground Techniques
–Remote sensing Techniques

•GEOMETRIC DESIGN
–Design Controls and Criteria
–Alignment design (vertical, horizontal)
–Cross-section elements
–Intersection Design and Control, Grade separated intersections
•PAVEMENT DESIGN
–Pavement types and structure,
–Structural design of pavements, stresses and strains in pavements
–Pavement maintenance and management

3. Lecture 1 on 01/02/07 3
Principles of Highway Location
Highway Location:
In relocation or establishment of new roads, surveys are required to
determine the most feasible location (route) of the highway that
will link predetermined locations. It is on the basis of this that
project plans are developed and costs estimated.
Highway location surveys may be accomplished in one of two ways;
using Conventional Ground Survey techniques or by Remote
Sensing.
Regardless of the specific approach adopted, the survey has to be
taken through four stages, namely:
–Desk study
–Reconnaissance survey
–Preliminary location survey
–Final location survey

4. Lecture 1 on 01/02/07 4
Principles of Highway Location
Conventional Ground Survey Technique
This is the more traditional and older approach. It is applied
generally, on projects of small to medium scale; but more
especially, in circumstances where the use of aerial
photographs is unsuitable or impossible.
Such instances are becoming less common with the rapid
developments in aerial photographic equipment and
photogrammetry.
The import of this technique is that the bulk of the location
party’s time and effort goes into measurement and observation
‘on the ground’. Otherwise it also goes through Desk studies,
Reconnaissance survey, Preliminary location survey and Final
location survey.

5. Lecture 1 on 01/02/07 5
Highway Location Surveys
Remote Sensing
Photogrammetry, often called ‘remote sensing’ is defined as the
science of obtaining measurements by means of photography. It
encompasses procedures for photo interpretation and converting
single photographs into composite ones and into maps.
Photogrammetry based on aerial photographs is an indispensable
working tool with application, not only in highway location but
also in:
–planning,
–geometric design,
–location of materials, and
–earthwork measurement, etc.

6. Lecture 1 on 01/02/07 6
Highway Location Surveys
•What is done at each stage?
–Desk Study
At this stage all possible sources of data in the form of maps, charts,
and aerial photographs must be explored and the data so obtained
evaluated.
Under Conventional Ground surveys, this will be a brief stage, as the
information to be examined is either non-existent, limited or may
not be very reliable.
The type and amount of data collected during desk studies will vary
according to the functional classification of the road and the nature
and size of the project.
Detailed analysis of all the available pertinent data can provide
valuable information to the engineer to enable him determine the
advisability of selecting a route.
The output of this stage is a series of proposed locations (in terms of
corridors) which may then be subjected to field or photogrammetric
investigations.

7. Lecture 1 on 01/02/07 7
Highway Location Surveys
Desk Study (cont’d)
Possible Data to look at during the Desk Study are:
–Engineering data
•Topographical and geological maps,
•Climatic records,
•Stream and drainage basin records
–Environmental data (e.g. Agric soil surveys on soil erode ability,
fish and wildlife inventories, water quality, wetlands, etc)
–Social data (e.g. demographic and land use information, zoning plans
and trends)
–Economic data (e.g. unit cost of construction, economic activities,
property values)

8. Lecture 1 on 01/02/07 8
Highway Location Surveys
(Area) Reconnaissance Study
This is usually the first significant step in the process of Ground Location Survey.
It consists of a field investigation to verify the conditions as determined from the
desk study. Generally, the engineer’s task at this stage is to obtain sufficient
information on the topography and nature of the area to determine which routes
deserve further study by ‘cut and try’.
A study is made of the profiles and grades of all alternative routes when using
Ground Location Techniques, and estimates made for grading, surfacing,
structures, and right-of-way. A comparison of alternative routes in this way will
aid the final selection of the most likely location.
When using photogrammetric techniques, at this stage control points between the
two terminal points are determined and flight lines between these control points
established. It is customary for the width of coverage to be about 0.4-0.6 the
distance between the control points.

9. Lecture 1 on 01/02/07 9
Highway Location Surveys
Reconnaissance Study (cont’d)
At this stage the location team should assess potential routes on the
basis of the following requirements:
–Directness of route
–Traffic service for population and industrial area
–Suitability of terrain encountered
–Adequacy and economy of crossings at watercourses and at
other transportation routes
–Extent of adverse social, environmental, and ecological
effects
During this phase of the location process, the range of alternative routes is
narrowed and a small number of routes are carried forward for further study.
The use of photogrammetric base maps often enables an objective study of all
possible routes with greater ease than field reconnaissance.

10. Lecture 1 on 01/02/07 10
Highway Location Surveys
•Preliminary Location Survey (selection of ‘P’
centerline)
After the preferred location has been established within a reasonably narrow band,
location on the ground (the traditional method) calls for a preliminary or ‘P’
line which will follow as closely as possible to the apparent position of the
final center line.
Using Ground Survey Techniques, at this stage the survey is made to gather
information about all physical features that affect the tentatively selected route.
In general the work is carried out by a regular survey party consisting of
–Party chief,
–Instrument man,
–Chainmen, and
–Rodmen.
A primary traverse or baseline is established. This is an open traverse consisting
of tangent distances and deflection angles following approximately the line
recommended in the reconnaissance report.

11. Lecture 1 on 01/02/07 11
Highway Location Surveys
Preliminary Survey (cont’d)
After establishing the P line, the topographic features are recorded. The extent
to the right and left of the traverse line to which the topography should be
determined will vary, and it is usually left to the judgment of the party chief.
In any case it should not be less than the proposed width of the right-of-way.
The amount of level work on preliminary survey should be minimal.
–No centerline profiles are needed in FLAT areas;
–In ROLLING terrain a profile of the traverse centerline would be
sufficient.
–In RUGGED terrain, a few cross sections are usually required in addition
to the centerline profiles.

The output from this stage is a preliminary survey map showing tangents with
bearings and distances, all deflection angles, ties to property corners or state
control monuments. Key topographic features are also included.

12. Lecture 1 on 01/02/07 12
Highway Location Surveys
Preliminary Survey (cont’d)
The preliminary survey based on photogrammetric (remote
sensing) methods is almost entirely an office operation.
Here, possible alternative alignments are plotted on the base map,
and from these alignments, with preliminary grade lines, the
alternatives are compared for suitability.
Key features examined and which form the basis of comparison
include:
–Design capacity,
–Safety,
–Road user costs,
–Construction costs, and
–Possible adverse environmental impacts.

13. Lecture 1 on 01/02/07 13
Highway Location Surveys
•Final Location Survey
The final location survey serves the dual purpose of permanently establishing the centerline
and collecting the information necessary for the preparation of plans for construction.
Conventionally, the method of establishing the final location in the field is by direct
chaining along tangents, I.e.
–First setting the points of intersection of tangent lines (PIs)
–Then closing out the horizontal curves between the tangents, using deflection angles
–Chaining to set the curve stations.
This method is still in use, although electronic distance-measuring (EDMs) have to a large
extent replaced chaining procedures.
Modifications of the final location may be made in the field when preliminary information
has been found to be inaccurate or incomplete. Level work is of utmost importance,
because the grade line, earthwork, and drainage are designed from level notes.
It is very important to keep good field note books on alignment and level surveys. Notes
taken in the field during the final location survey usually become part of the permanent
record of the project.

14. Lecture 1 on 01/02/07 14
Highway Location Surveys
Problems of Highway Location in Urban Areas
In rural areas, the location of a highway is dictated mainly by the
the desired end-points of travel, topography, geology, and
environmental impact. In urban areas the location process is
more involved, reflecting the complexities of urban conditions.
Among conditions that control urban locations are:
–Traffic Service: As a result of extensive investigations of travel desires
and existing travel patterns in an urban area, the traffic planner can predict
the effect on travel patterns of alternative locations of proposed highways.
Thus the location engineer can determine how well alternative locations
will fit with existing network and identify desirable locations that conform
to travel desire lines.
–Land-use: The link between land-use and traffic generation is well
known. Constraints in this respect may be, e.g. for health and safety
reasons, do not locate heavily trafficked routes through residential areas.

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Highway Location Surveys
Problems of Highway Location in Urban Areas
–Off-street Parking: Parking is a crucial need in urban
areas.Ideally, the location of new routes should be close to
existing and potential parking facilities for the vehicles
attracted onto the new facility.
–Inter-modality: Location of a new facility should not disrupt
existing transportation service, since the aim is to increase
the overall level of service of transportation in the urban
area. Coordination with other modes of transport is essential
to ensure a balanced development
–Relocation of utilities
–Social effects: New road should not lead to community
severance, nor should they take up open public land

16. Lecture 1 on 01/02/07 16
GEOMETRIC DESIGN OF HIGHWAYS
Definition:
Geometric design is the process whereby the layout of the road in the terrain is
designed to meet the needs of the road users. In other words, it is concerned
with relating the physical elements of the highway to the requirements of the
driver and the vehicle. Geometric design does not include structural design
of pavements.
Features which need to be considered in geometric design are:
–Horizontal and vertical alignment,
–The cross-section elements (including noise barriers),
–Highway grades, and
–Layout of intersections
The design of these features is considerably influenced by driver behaviour and
psychology, vehicle characteristics and trends, and traffic speeds and
volumes.
While proper geometric design should provide for safety and efficiency of
operation, it is important that the highway designed presents an aesthetically
satisfying picture. The design must blend harmoniously with the topography
as much as possible.