Highway Engineering

Subject Code - CE 2255

 Topics

Session Topics to be covered Time Ref Teaching Method

No
Highway Cross-
sectional Elements –
Right of Way,
Carriageway, Camber,
07 50 min 1, 2 PPT
kerbs, Shoulders and
Footpaths (IRC
Standard), C/S of
different class of roads
 Right of Way
Right of Way (RoW) is the area of land acquired for the

road, along its alignment. The width of this acquired

land 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.

 Land Width
A desirable range of land width has also been

suggested for each category. While acquiring land for a

highway it is desirable to acquire more width of land as

the cost of adjoining land invariably increase very

much, soon after the new highway is constructed.

 Land Width (IRC)
Plain and Rolling Terrain Mountainous and Steep terrain
Road
Classificat Open Areas Built-up Areas Open Areas Built-up Areas
ion
Normal Range Normal Range Normal Range Normal Range

NH/SH 45 30-60 30 30-60 24 -- 20 --

MDR 25 25-30 20 15-25 18 -- 15 --

ODR 15 15-25 15 15-20 15 -- 12 --

VR 12 12-18 10 10-15 9 -- 9 --
 Building lines & Control lines
It is desirable to control the building construction

activities on either sides 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 disallow the building

activities up to “building line” with sufficient setbacks

from the road boundary.

 Building lines & Control lines
In addition, it is desirable so exercise control of nature

of building up to further set back distance up to the

“Control lines.” The overall width requirements

between the building line and between the control lines

on either side of the road, recommended by IRC are

given below:
 Building & Control line (IRC)
Plain and Rolling Terrain Mountainous and Steep terrain

Road Distance b/w building line and

Open Areas Built-up Areas
Classificat Road boundary (setback)
ion Overall Overall Distance b/w
width b/w width b/w building line and Open areas Built-up areas
BL CL Road boundary

NH/SH 80 150 3 to 6 3 to 5 3 to 5

MDR 50 100 3 to 5 3 to 5 3 to 5

ODR 25/30 35 3 to 5 3 to 5 3 to 5

VR 25 30 3 to 5 3 to 5 3 to 5
 Short Conclusion
It can be seen that the normal land width required for

NH/SH on open plain terrain is 45 m and the maximum

land width required is 60 m, the corresponding width

b/w the building lines is 80 m and that b/w the control

line is 150m, thus allowing setback distance of 10 to 45

m beyond the road boundary lines with the max.

recommended road width.

 Urban Roads
The recommended land width for different classes of

urban roads are, 50-60 m for arterial roads (high types

of urban roads meant for through traffic, with controlled

access), 30-40 m for sub-arterials, 20-30 m for collector

roads, and 10-20 m for local streets.

 Carriageway
The pavement or carriageway width depends on the

width of traffic lane and number of lanes. The

carriageway intended for one line of traffic movement

may be called a traffic lane. The lane width is

determined on the basis of the width of vehicle and the

minimum side clearance which may be provided for the

safety.
 Carriageway
When the side clearance is increased (upto a certain

limit) there is an increase in operating speed of vehicles

and hence increase in capacity of the traffic lane.

Keeping all these in view a width of 3.75 m is

considered desirable for a road having single lane for

vehicles of maximum width 2.44 m. for pavement

having two or more lanes width of 3.5 m/lane is

considered sufficient.
 Carriageway

The maximum width of vehicle as per IRC

specifications is 2.44 m. If a single lane carriageway of

width 3.8 m is provided, a side clearance of 0.68 m

would be obtained. In the case of two lane road (7.0 m)

clearance between two vehicles is 1.06 m.

 0.65 m
0.65 m

2.5 m

3.8 m

0.5 m
0.5 m 1.0 m

2.5 m 2.5 m

7.0 m
 Carriageway

In some highways, traffic separators or medians are

provided between two sets of traffic lanes intended to

divide the traffic moving in opposite direction. In such

highways, road width depends on the pavement width

and the width of traffic separators.

 Class of Road Width of Carriageway

Single lane 3.75 m

Two lane without raised kerb 7.0 m

Two lane with raised kerb 7.5 m

Intermediate carriageway (except on important 5.5 m
roads)
Multi-lane pavements 3.5 m per lane

Note
1. The width of single lane or village roads may be decreased to 3 m
2. On urban roads without kerbs the single lane width may be decreased to
3.5 m and in access road to residential areas to 3.0 m
3. The minimum width recommended for kerbed urban road is 5.5 m to make
allowance for a stalled vehicle
 Cross Slopes or Camber

Cross slope or camber is the slope provided to the road

surface in the transverse direction to drain off the rain

water from the road surface. Drainage and quick

disposal of water from the pavement surface by

providing cross slope is considered important because

of two reasons:
 Cross Slopes or Camber

• To prevent the entry of surface water into the sub-

grade soil through pavement; the stability, surface

condition and the life of the pavement get adversely

affected if the water enters into the sub-grade and the

soil gets soaked.

 Cross Slopes or Camber

• To prevent entry of water into the bituminous

pavement layers, as continued contact with water

causes stripping of bitumen from the aggregates and

results in deterioration of the pavement layer.

 Cross Slopes or Camber

• To remove the rain water from the pavement surface

as quickly as possible and to allow the pavement to

get dry soon after the rain; the skid resistance of the

pavement gets considerably decreased under wet

condition, rendering it slippery and unsafe for vehicle

operation at high speeds.

 Cross Slopes or Camber

Usually the camber is provided on the straight roads by

raising the centre of the carriageway with respect to the

edges, forming a crown or highest point on the centre

line. The rate of camber usually designated by 1 in n or

X% of cross slope. Recommended values of camber

values are given below:

Sl. No. Type of Road Surface Range of camber in areas of
rainfall range
Heavy Light
1 Cement Concrete or High type 1 in 50 (2.0%) 1 in 60 (1.7%)
bituminous surface

2 The bituminous surface 1 in 40 (2.5%) 1 in 50 (2.0%)

3 Water bound macadam or gravel 1 in 33 (3.0%) 1 in 40 (2.5%)

pavement

4 Earth 1 in 25 (4.0%) 1 in 33 (3.0%)

 Kerb

Kerb indicates the boundary between the pavement and

shoulder; or sometimes island or footpath or kerb

parking space.
 Kerb

It is desirable to provide kerbs on urban roads. Kerbs

may be divided into three groups based on their

function.

•Low or mountable type kerb

•Semi-barrier type kerb

•Barrier type kerb

 Low/ Mountable Kerb
Encourage traffic to remain in the through traffic lanes,

yet allow the driver to enter the shoulder area with little

difficulty. This type is provided at

median/channelization/longitudinal drainage.

Max. height – 10 cm
 Semi-mountable Kerb
Provided on the perifery of a roadway where the

pedestrian traffic is high. It prevents encroachment of

parking vehicles.

Max. height – 15 cm
above pavement edge
 Barrier Kerb
Provided in built-up areas adjacent to footpath with

considerable pedestrian traffic.

Max. height – 20 cm
above pavement edge
No Comments
 Shoulder
Shoulders are provided along the road edge to serve as

an emergency lane for vehicle compelled to be taken

out of the pavement or roadway. Shoulders also act as

service lanes for vehicles have broken down. The width

of shoulder should be adequate to accommodate

stationary vehicle fairly away from the edge of adjacent

lane.
 Shoulder
The minimum shoulder width recommended by the IRC

is 2.5 m. the shoulder should have sufficient load

bearing capacity to support loaded truck even in wet

weather. The surface of the shoulder should be rougher

than the traffic lanes so that vehicles are discouraged

to use the shoulder as regular traffic lane.

 Footpath or Sidewalk
Footpaths are provided in urban areas when the

vehicular as well as pedestrian traffic are heavy, to

provide protection to pedestrians and to decrease

accidents. Side walks are generally provided on either

sides of the road and the minimum width should be 1.5

m and the width may be increased based on the

pedestrian traffic volume.