Question

What is the minimum length of a transition curve for a design speed of 80 kmph in a horizontal curve of 240 m radius?

• A. 72 m
• B. 42 m
• C. 32 m
• D. 52 m

Answer 1

The correct option is A 72 m

Rate of change of centrifugal acceleration
$C=\frac{80}{75+V}=\frac{80}{75+80}$
$=0.516m/s^3$
Length of transition curve,
$L_s=\frac{v^3}{CR}$
$=\frac{{\left(\frac{80}{3.6}\right)}^3}{0.516\times 240}$
$=88.6\simeq 89m$
For plain and rolling terrain (by default)
$L_s=\frac{2.7V^2}{R}=72m$
Since 72 m is one option so it should be chosen.