Centrifugal ratio limit for comfort on highways: For comfortable travel on a horizontal curve, the centrifugal ratio (lateral force to weight) should not exceed which value?

Introduction / Context:
Vehicle lateral comfort and safety on curves depend on the balance between centripetal demand and the resisting effects of roadway superelevation and tire-road friction. Designers control the allowable “centrifugal ratio” to avoid uncomfortable side-thrust and skidding.

Given Data / Assumptions:

• Centrifugal ratio = lateral force / weight.
• Standard passenger vehicles on paved roads.
• Normal design climates and speeds.

Concept / Approach:
Conventional highway design limits the lateral acceleration felt by occupants to maintain comfort and safety. A widely used comfort criterion is to limit the centrifugal ratio to about 0.10, with the remaining requirement met by superelevation and friction within safe bounds.

Step-by-Step Solution:
Recognize centrifugal ratio as a comfort proxy.Adopt the standard comfort limit ~0.10 for routine design.Use this limit with permissible superelevation and friction to size curve radius.

Verification / Alternative check:
Empirical relationships used in design (e + f = V^2 / (225 * R) in km/h units) align with keeping experienced lateral acceleration within comfort limits near 0.10 for typical facilities.

Why Other Options Are Wrong:

• 0.15–0.30: represent stronger lateral acceleration; can be uncomfortable/unsafe under normal road conditions.

Common Pitfalls:

• Confusing centrifugal ratio with side-friction factor; both are related but not identical in interpretation.
• Not reducing limits in icy/snowy climates where friction is lower.

Final Answer:
0.10