Highway design (IRC): For a national highway on plain terrain with ruling design speed 100 km/h, maximum superelevation e = 0.07 and lateral friction f = 0.15, the ruling minimum radius of the horizontal curve is closest to what value?

Question

Solve this multiple-choice question and choose the correct option.

Accepted Answer

Introduction / Context:Horizontal curve radius ensures that lateral acceleration is balanced by superelevation and side friction at the chosen design speed. IRC practice provides a simple formula relating speed, superelevation, and friction to the minimum safe radius. Given Data / Assumptions: Design speed V = 100 km/h. Maximum superelevation e = 0.07. Coefficient of lateral friction f = 0.15. Use standard IRC formula for R (with V in km/h). Concept / Approach:The IRC relation is R = V^2 / [225 * (e + f)], where R is in metres. This assumes small-angle approximations and combines gravitational component on the bank with frictional resistance against centripetal demand. Step-by-Step Solution: Compute e + f = 0.07 + 0.15 = 0.22.Compute denominator: 225 * 0.22 = 49.5.Compute R: 100^2 / 49.5 = 10,000 / 49.5 ≈ 202 m.Select the closest option provided: 250 m (closest to ≈ 200 m among choices). Verification / Alternative check: A sensitivity check with modest rounding of f or e (field practicability) still yields a radius near 200–230 m, supporting selection of 250 m as the nearest listed value. Why Other Options Are Wrong: 360 m and 300 m: materially larger than the computed ruling minimum.36 m: orders of magnitude too small for 100 km/h. Common Pitfalls: Using V in m/s without converting the formula constant; forgetting to include both e and f. Final Answer: 250 m

Highway design (IRC): For a national highway on plain terrain with ruling design speed 100 km/h, maximum superelevation e = 0.07 and lateral friction f = 0.15, the ruling minimum radius of the horizontal curve is closest to what value?

More Questions from GATE Exam Questions

Discussion & Comments