# How to Calculate Stopping Sight Distance – Mathematical Example

2nd April 2019Contents

## 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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