Question

The extra widening required for a National highway curve in a plain terrain with a radius of 220 m and 7 m wheel base is:

• A. 0.62 m
• B. 0.72 m
• C. 0.82 m
• D. 0.92 m

Hint:

Mechanical widening ($n l^2 / 2R$) depends only on vehicle and road geometry, while psychological widening ($V / 9.5\sqrt{R}$) depends on the driver's comfort at high speeds.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:

• Find the extra widening of a curve of radius \( R = 220 \text{ m} \) with wheel base \( l = 7 \text{ m} \) on a National highway in plain terrain.

Step 2: Detailed Explanation:

• Extra widening \( W_e = \dfrac{n l^2}{2R} + \dfrac{V}{9.5\sqrt{R}} \), taking a two-lane road (\( n = 2 \)) and a design speed \( V \approx 100 \text{ km/h} \).

• Mechanical widening \( = \dfrac{2 \times 7^2}{2 \times 220} \approx 0.22 \text{ m} \).

• Psychological widening \( = \dfrac{100}{9.5 \times \sqrt{220}} \approx 0.71 \text{ m} \).

• \( W_e \approx 0.93 \text{ m} \), closest to 0.92 m.

Step 3: Final Answer:
The correct option is (D) 0.92 m.