GLOSSERY
TERMS
[1] RIGHT OF WAY: - It
is defined as the land width acquired along the alignment of road. The land
width of road will depend on its importance and future development. A minimum
land width for different category of roads and different locations has been
fixed by I.R.C. The land width is governed by the following factors.
(i)
It primarily depends on the category of roads, e.g, national highway, state
highway, district road and village road.
(ii)
Height of embankment or depth of cutting will also matter in deciding the land
width.
(iii)
Side slopes and soil types.
(iv)
Drainage system and catchment areas.
[2] ROAD CAMBER: -The
highest point on the surface is called crown. The word ‘camber’ is defined as
the slope of the line joining the crown and the edge of the road surface. Thus
a camber of 1 in 30 means that for a 30mt wide road the crown of the road will
be 0.5mt above the edge of the road. The recommended camber for different types
of roads are as:
|
SN |
Types Of Road |
Recommended Camber |
|
1 |
Earth
roads and Foothpath |
1
in 20 to 1 in 24 |
|
2 |
Gravel
Road |
1
in 24 to 1 in 30 |
|
3 |
Murum
road or Kankar road |
1
in 24 to 1 in 30 |
|
4 |
Water
Bound Macadum road |
1
in 30 to 1 in 48 |
|
5 |
Bituminous
road |
1
in 48 to 1 in 60 |
|
6 |
Cement
Concrete roads |
1
in 60 to 1 in 72 |
[3] SUPER ELEVATION: - Super
elevation is defined as the inward tilt or transverse inclination given to the
cross section of the road surface, throughout the length of the horizontal
curve to reduce the effect of centrifugal force on the running wheels. It is
also sometimes known as Cant or Banking. OR
It
is expressed as the difference of heights of two edges of the carriageway to
the width of the carriageway. Thus a super elevation of the 1 in 20 means that
for a 20mt wide road the outer edge of the carriageway is 1mt above the inner
edge at the vertex of the horizontal curve. It is denoted by ‘e’.
e
= v2 / 127R
Here, v = speed in kilometers per hour
and R is radius of curvature in metres and s = width of road in metres.
[4] ROAD GRADIENT: - The
rate of rise or fall of the road surface along its length is called gradient.
It is expressed as the ratio of the difference of heights between the two
points and the distance between them.
If
the difference of levels between two points A and B is 1metre and their
distance apart is 50 metre, the gradient is said to be 1 in 50. It is also
expressed as a percentage,
i.e,
(1/50) x 100 = 2%
The
gradient of roads depend upon following factors:
(i)
Nature of Traffic (ii) Nature
of Ground (iii)
Rainfall of the Locality.
