Question

The ruling design speed on a National Highway in plain terrain as per IRC recommendations is ____

• A. \(60\ \mathrm{kmph}\)
• B. \(80\ \mathrm{kmph}\)
• C. \(100\ \mathrm{kmph}\)
• D. \(120\ \mathrm{kmph}\)

Hint:

IRC ruling design speeds: \[ \boxed{ \begin{aligned} \text{Plain terrain} &\rightarrow 100\ \mathrm{km/h}\\ \text{Rolling terrain} &\rightarrow 80\ \mathrm{km/h}\\ \text{Mountainous terrain} &\rightarrow 50\ \mathrm{km/h}\\ \text{Steep terrain} &\rightarrow 40\ \mathrm{km/h} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Recall what ruling design speed decides.
Ruling design speed sets the geometric design elements of a highway, things like minimum curve radius and sight distance, and it depends heavily on the terrain the road passes through.
Step 2: Compare plain terrain to hilly terrain.
Plain terrain imposes almost no restriction from gradients or sharp curvature, so vehicles can safely be designed for higher speeds than on rolling or mountainous terrain.
Step 3: Recall the fixed IRC value.
For National Highways and State Highways running through plain terrain, IRC guidelines fix the ruling design speed at this higher value.
\[ \boxed{100\ \mathrm{kmph}} \]