Civil Engineering

Calculate Stopping Sight Distance

Mathematical Example

Calculate stopping sight distance for 

i) Two lane road with two way traffic.
ii) Single lane road with two way traffic.
Design speed is 50 Km/h, Coefficient of friction is 0.4, and the reaction time of the driver is 3 sec. The road is level.

Mathematical Solution of Stopping Sight Distance

Given, design speed (V) = 50 Km/h, reaction time of driver(t) = 3 sec, coefficient of friction between tire and road surface(f) = 0.4

We know, for descending gradient,
Stopping sight distance = (0.278V.t + V²/254f)
= 0.278  50 ⨯ 3 + 50²/254 ⨯ 0.4 
= 66.3 m.
Stopping Sight Distance
i) For two-lane road with two way traffic = 66.3 m
ii) For single lane road with two way traffic = 2⨯66.3 = 132.6 m
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