Multiple choice

A horizontal circular curve with a centre line radius of 200 m is provided on a 2-lane, 2-way SH section. The width of the 2-lane road is 7.0 m. Design speed for this section is 80 km per hour. The brake reaction time is 2.4s, and the coefficients of friction in longitudinal and lateral directions are 0.355 and 0.15, respectively.

The safe stopping sight distance on the section is

  1. 221 m

  2. 195 m

  3. 125 m

  4. 65 m
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C Correct answer
Explanation

Stopping Sight Distance (SSD) is calculated as SSD = v*t + v^2 / (2*g*(f +/- G)). Given v = 80 km/h = 22.22 m/s, t = 2.4 s, and f = 0.355, SSD = 22.22*2.4 + (22.22^2) / (2*9.81*0.355) = 53.33 + 71.07 = 124.4 m, which rounds to 125 m.

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