# 6 Stopping Sight Distance Formula

## 6 Stopping Sight Distance Formula

The stopping sight distance formula, based on the road surface condition and speed of the vehicle units(m/sec or km/h) is divided into 6 types:

### A. Level Surface With Friction Coefficient

Stopping Sight distance formula(SSD) for the level surface with a coefficient of friction:

1. SSD = Vt + V2/2gf  (when V in m/sec).

2. SSD = 0.278 Vt + V2/254f (when V in km/h).

### B. Inclined Surface with Coefficient of Friction

Stopping Sight distance formula(SSD) for the inclined surface with a coefficient of friction. Where ‘n’ % gradient.

1. SSD = Vt + V2/2g(f ± 0.01n)  when V in m/sec.

2. SSD = 0.278Vt + V2/254(f ± 0.01n)  when V in km/h

Where ‘n’ % gradient and + sign for ascending gradient, – sign for descending gradient.

### C. Level Surface With Braking Efficiency

Stopping Sight distance formula(SSD) for the level surface with braking efficiency η.

1. SSD = Vt + V2/2gfη  where V in m/sec.

2. SSD = Vt + V2/254fη   where V in km/h.