How To Calculate Minimum Non-Passing Sight Distance -Mathematical Example

30th March 2019 0 By Malay Sautya

Mathematical Example

Calculate the minimum non-passing or say stopping sight distance on a highway at a descending gradient of 6% with following data:  a) Design speed = 80 Km/h, b) Reaction time of driver = 2.5 Sec, c) Coefficient of friction between tire and road surface = 0.4

Mathematical Solution

Given, 

a) Design speed(V) = 80 Km/h
b) Reaction time of driver(t) = 2.5 Sec
c) Coefficient of friction between tire and road surface(f) = 0.4
d) Gradient (n) = 6%  

We know, for descending gradient,

Stopping sight distance/non passing Sight distance 
= 0.278V.t + V²/254(f-0.01n)
= 0.278 ⨯ 80 ⨯ 2.5 + 80² / 254(0.4 – 0.01⨯6)
= 129.71 m

Answer: Non-Passing sight distance or say stopping sight distance should be 129.71 m