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What is the mechanical extra widening required for a two-lane pavement of width 7 m on a horizontal curve of radius 250 m, if the longest wheelbase of a vehicle expected on the road is 5 m with a design speed of 70 km/h ?

If the number of traffic lanes are n, then total extra width (Wm) required for pavement is given by

\({W_m} = \frac{{n{l^2}}}{{2R}}\)

This is called mechanical widening and takes into account only the first factor listed above.

Calculation:

Given,

Width of road = 7 m
l = 5 m
R = 250 m
V = 70 kmph

For pavements having two or more lanes, width of 3.5 m per lane

Number of lanes n = 7/3.5 = 2

\({W_m} = \frac{{2 \times {5^2}}}{{2 \times 250}}\)

= 0.1 m