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.
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