Civil Engineering

# Find The Stopping Sight Distance To Avoid Head on Collision

Here, a mathematical problem is taken to determine the value of minimum stopping sight distance to avoid head-on collision of two cars, when the value of the braking efficiency is given.

## Mathematical Problem

Find minimum stopping sight distance to avoid head-on collision of two cars approaching at 90 Km/h and 60Km/h. Use reaction time 2.5 sec, coefficient of longitudinal friction is 0.7 and brake efficiency of 50 percent in either case.

## Mathematic Solution

Given,
• V1 = 90 Km/h
• V2 = 60 Km/h
• t = 2.5 sec
• f = 0.7
• Braking efficiency (η) =50% =0.5( note: brake efficiency reduces the coefficient of friction by 50%)

now,

Stopping Sight Distance of first car (SSD1
(0.278V.t + V²/254fη)
= 0.278⨯90⨯2.5 + 90²/254⨯0.7⨯0.5
= 153.6m
Stopping Sight Distance of second car(SSD2)
(0.278V.t + V²/254fη)
0.278⨯60⨯2.5 + 60²/254⨯0.7⨯0.5
= 82.19m
so, stopping sight distance to avoid head-on collision of the two approaching cars (SSD) = SSD1SSD2 = (153.6+82.19) =235.79m