Question

A vehicle of speed 80 kmph traverses a circular curve of radius 300 m in plain and rolling terrain where pavement width is 7 m. If the rate of introduction of super elevation is 1 in 150, the length of transition curve required considering only rate of introduction of super elevation and the pavement is rotated about inner edge is

• A. 48.75 m
• B. 57.6 m
• C. 36.75m
• D. 73.5m

Answer 1

The correct option is D 73.5m

Super elevation rate
$e=\frac{V^2}{225R}=\frac{{80}^2}{225\times 300}=0.094$

This value is more than the permissible value of 0.07. Hence limit e to 0.07

Lateral friction coefficient = f
$=\frac{V^2}{127R}-e=\frac{{80}^2}{127\times 300}-0.07=0.0979$

Since this value is less than 0.15, it is safe

Length of transition curve required if the pavement is rotated about inner edge,

$=eNB=0.07\times 150\times 7=73.5m$