Width of formation or Roadway , Right of way and land width, Typical cross sections of road

Width of formation or Roadway , Right of way and land width, Typical cross sections of road

1. DEPARTMENT OF CIVIL ENGINERRING Width of Formation or Roadway Right of Way and Land Width Typical Cross Sections of Roads Er . Ramprasad Kumawat M.Tech

2. Width of Formation or Roadway Width of formation or roadway is the sum of widths of pavement or carriageway including separators, if any and the shoulders. Formation or roadway width is the top width of the highway embankment or the bottom width of highway cutting excluding the side drains . Refer in Fig.

3. The width of roadway standardized by the Indian Road Congress is given table 4.3

4. Notes: (a) In multilane highways, roadway width should be adequate for the requisite number of traffic lanes besides shoulders and central median. (b) The minimum roadway width on single lane bridge is 4.25 m.

5. Right of Way and Land Width Right of way is the area of land acquired for the road, along its alignment. The width of the acquired land for right of way is known as 'land width' and it depends on the importance of the road and possible future development . A minimum land width has been prescribed for each category of road. A desirable range of land width has also been suggested for each category of road.

6. While acquiring land for a highway it is desirable to acquire more width of land as the cost of adjoining land invariably increases very much, soon after the new highway is constructed. Also road side developments start taking place making it difficult later on to acquire more land required for future widening or for other improvements . In some cases the lower width within the suggested range may have to be adopted in view of high cost of land and other existing features. This is particularly true in urban and industrial areas

7. The land width is governed by the following factors: ( a) Width of formation which depends on the category of highway, width of roadway and road margins (b) Height of embankment or depth of cutting which is governed by the topography and the vertical alignment (c) Side slopes of embankment or cutting which depend on the height of the slope, soil type and several other considerations including aesthetics

8. (d) Drainage systems and their size, which depends on the rainfall, topography, and run off (e) Sight distance considerations on horizontal curves, as there is restriction to the visibility on the inner side of the curve due to obstruction such as building structures etc. At sharp curves it is desirable to acquire a wider strip of land, particularly on the inner side of the horizontal curve in order to avoid obstructions to visibility . Refer Fig 4.5

9. (f) Reserve land for future widening is to be planned in advance based on anticipated future development and increase in the traffic. The values of normal and range of land width standardized by the IRC for various categories of roads in rural areas and in different terrains a re given in table 4.4

10. It is desirable to control the building construction activities on either side of the road boundary, beyond the land width acquired for the road in order to reserve sufficient space for future improvement of roads. Therefore , it is necessary to prohibit the building activities up to 'building line' with sufficient setback from the road boundary. In addition it is desirable to exercise control of the nature of building up to f urther set back distance up to the 'control lines'.

11. The overall width requirements between the building lines and the control lines on either side of the road, recommended by the IRC for different road classifications and different terrain conditions in rural areas are given in Table 4.5.

12. It may be seen from Tables 4.4 and 4.5 that the normal land width required for the National and State Highways on open plain terrain is 45 m and the maximum land width required is 60 m, the corresponding width between the building lines is 80 m and that between the control lines is 150 rn , thus allowing set back distances of 10 and 45 m beyond the road boundary lines with the maximum recommended road width.

13. *Split levels The recommended land widths for different classes of urban roads are, 50 to 60 m for arterial roads (high types of urban roads meant for through traffic, with controlled access), 30 to 40 m for sub-arterial roads, 20 to 30 m for collector streets (urban roads and streets meant for collecting traffic from local streets and feed to the arterial and sub-arterial roads) and 10 to 20 m for local streets.

14. Typical Cross Sections of Roads Some of the typical cross sections of different categories of highways in rural areas and a typical urban arterial road are shown in Fig. 4.6 to 4.10.

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