Question

The maximum ruling gradient in a rolling terrain according to IRC can be

• A. 1 in 15
• B. 1 in 60
• C. 1 in 90
• D. 1 in 30

Hint:

IRC ruling gradients: \[ \boxed{ \begin{aligned} \text{Plain/Rolling} &\rightarrow 1:30\\ \text{Mountainous} &\rightarrow 1:20\\ \text{Steep} &\rightarrow 1:16.7 \end{aligned} } \]

Answer 1

The Correct Option is D

Step 1: Recall how terrain is classified.
IRC classifies terrain by the average cross slope of the ground, plain, rolling, mountainous, and steep, each getting progressively steeper permissible gradients.
Step 2: Recall the IRC ruling gradient table.
The typical ruling gradients are 1 in 30 for plain and rolling terrain, 1 in 20 for mountainous terrain, and 1 in 16.7 for steep terrain, with somewhat flatter values allowed in exceptional cases.
Step 3: Pick the value for rolling terrain.
Rolling terrain falls in the same category as plain terrain in this table, so its ruling gradient is 1 in 30.
\[ \boxed{1 \text{ in } 30} \]