Hi,
It is observed that pavement width, at the horizontal curves, are somewhat larger than the width on the straight roads. This extra width is the result of extra widening of the pavement at the curves. The reasons behind this are as follows.
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The wheelbase of the vehicles is rigid and therefore while taking the turn, only front wheels are able to change direction. The path travelled by the front wheels will be different and at certain distance outwards from the path traced by the rear wheels. This can be understood with the help of the diagram and image shown below.
Extra widening on horizontal curves - There is a tendency of the driver to take the outer path at the curves to have more sight distance visible ahead.
- While overtaking operations on horizontal curves driver will need more spacing from the other vehicles to feel safer.
Widening of the Pavement on the Horizontal Curves
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| A horizontal curve on a hilly road (At Govind Sagar Lake viewpoint, Himachal Pradesh) |
Widening of the pavement on the horizontal curves is governed by the following factors.
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Length of the wheelbase
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The radius of the curve negotiated, R
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The psychological factor which depends upon the velocity of the vehicle and the Radius of the curve.
In general, extra width is provided on the horizontal curves when the radius is less than 300 m.
Extra widening = mechanical Widening + Psychological Widening
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| IRC recommended values for the Extra widening of pavement on Horizontal curves |
We = Wm + Wps
We = nl^2/ 2R + V/ [9.5R^(1/2)]
Here, n = number of traffic lanes
l = Length of the wheelbase
V= Design speed in kmph
R = Radius of the horizontal curve in m
The figure given above shows the IRC recommended values of the extra width for the curves of different radius.
Thanks for your kind visit!
If no. Of lanes not given and width is given then how to Calculate no.of lanes?
The extra mechanical widening required for 14 m wide pavement on a horizontal curve of radius R is given by…..
what will use if length of wheel base is not given?