Recommended camber for earth roads to ensure drainage For road surfaces constructed in earth (earthen roads), which range of camber is generally preferred to quickly drain rainwater while limiting erosion?

Introduction / Context:
Camber provides the necessary transverse slope for water to run off the road surface. Earth roads are more permeable and susceptible to rutting and erosion, so the camber must be sufficient to shed water without causing discomfort or instability.

Given Data / Assumptions:

• Surface type: earth (unsealed) road.
• Objective: adequate drainage with reasonable riding comfort.

Concept / Approach:
Typical practice recommends higher camber for earth roads than for bituminous or concrete pavements. A range of 1 in 20 to 1 in 24 (about 5% to 4.2%) offers a sound balance: swift drainage yet not so steep as to cause lateral instability or edge erosion.

Step-by-Step Solution:
Identify surface type → earth requires higher camber.Select the commonly recommended range → 1 in 20 to 1 in 24.Confirm that steeper alternatives (e.g., 1 in 10) are excessive for ordinary traffic comfort.

Verification / Alternative check:
Design guides generally assign maximum camber to earth roads, intermediate to water-bound macadam, and lower to bituminous/concrete.

Why Other Options Are Wrong:
Steeper ranges (1 in 10–1 in 15) risk rilling/erosion and discomfort; flatter ranges (1 in 30–1 in 48) may drain too slowly on unsealed surfaces.

Common Pitfalls:
Applying urban paved-road camber values to earth roads; ignoring rainfall intensity and soil erodibility in local adjustments.

Final Answer:
1 in 20 to 1 in 24