Q1: While aligning a hill road with a ruling gradient of 1 in 20, horizontal curve of radius 80 m is encountered. The compensated gradient on the curve will be

ANS:C - 1 in 25

Since 1 in 20 is higher than 4% as per IRC Compensation is required.

Grade Compensation is (30+R)/R % where R is Horizontal curve.
But Maximum Compensation is limit to 75/R %.

Hence 75/80=0.9375%.
1 in 20 = 5 %.
Compensation = 5-0.9375= 4.0625 % ~ 4%.

Hence Compensated gradient on the curve is 4% = 1 in 25.