Question

A constant value of coefficient of lateral friction as recommended by IRC is

• A. 0.15
• B. 0.40
• C. 0.35
• D. 0.30

Hint:

The coefficient of lateral friction is a critical parameter in road design, ensuring vehicles can safely navigate curves. The IRC’s value of 0.15 is a conservative estimate, accounting for varying road conditions like wet surfaces, to prioritize safety.

Answer 1

The Correct Option is A

Step 1: Identify the given data.
The question asks for the constant value of the coefficient of lateral friction as recommended by the Indian Roads Congress (IRC). The options are:
(1) 0.15
(2) 0.40
(3) 0.35
(4) 0.30
We need to determine the IRC-recommended value for the coefficient of lateral friction.
Step 2: Recall the role of the coefficient of lateral friction in road design.
The coefficient of lateral friction (\( f \)) is a key parameter in the design of horizontal curves on roads. It represents the friction between the vehicle’s tires and the road surface, which helps counteract the centrifugal force experienced by a vehicle on a curve. The IRC provides guidelines for this coefficient to ensure safe vehicle operation, particularly when super-elevation alone is insufficient to balance the centrifugal force.
Step 3: Determine the IRC-recommended value.
According to IRC guidelines (e.g., IRC:73 for geometric design of roads), the coefficient of lateral friction is typically set at a conservative value to ensure safety across various road conditions (e.g., wet surfaces). The IRC recommends a constant value of 0.15 for the coefficient of lateral friction for design purposes. This value is used in the design of horizontal curves when calculating the required super-elevation and ensuring vehicle stability:
\[ e + f = \frac{V^2}{gR} \] Where:
\( e \): Super-elevation
\( f \): Coefficient of lateral friction
\( V \): Design speed (m/s)
\( g \): Acceleration due to gravity (9.81 m/s²)
\( R \): Radius of the curve (m)
The value of 0.15 is a standard assumption for most road types, balancing safety and practicality.
Step 4: Compare with the options.
0.15 (Option 1) matches the IRC-recommended value.
0.40 (Option 2) is too high; such a value would imply an unrealistically high friction coefficient, not suitable for safe design.
0.35 (Option 3) is also higher than the IRC standard.
0.30 (Option 4) is closer but still exceeds the recommended value of 0.15.
Step 5: Select the correct option.
The IRC-recommended constant value for the coefficient of lateral friction is 0.15, matching option (1).
\[ \boxed{0.15} \]