How to Calculate Stopping Sight Distance – Mathematical Example

Stopping Sight Distance Problem And Solution

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

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.

Answer: 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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