Correct Answer - Option 3 : 4.75%
Given:
Ruling gradient of hilly road = 6%
Radius of curve (R) = 60 m
Calculation:
Grade compensation = \(\frac{{30\; + \;R}}{R}\% \)
= \(\frac{{30\; + \;60}}{{60}}\% \) = 1.5%
This should not be more than
= \(\frac{{75}}{R}\% \) = \(\frac{{75}}{{60}}\% \) = 1.25%
Compensated gradient = Ruling gradient – Grade compensation
= 6% – 1.25% = 4.75%