For hill roads with a thin bituminous surfacing, what is the minimum camber (cross slope) that should be provided to ensure adequate drainage and skid resistance?

Introduction / Context:
Camber is the transverse slope given to road surfaces to quickly drain rainwater, thereby minimizing water film thickness, improving skid resistance, and protecting the pavement layers. Hill roads often experience higher rainfall and steeper grades, necessitating slightly higher cambers than in plains, especially for thin bituminous surfaces.

Given Data / Assumptions:

• Terrain: hilly region.
• Surface type: thin bituminous treatment (e.g., surface dressing).
• Objective: choose the minimum recommended camber to ensure drainage.

Concept / Approach:
IRC practice recommends camber ranges by surface type and terrain. For thin bituminous surfaces on hill roads, a minimum around 3.0% is commonly adopted to provide reliable drainage without causing discomfort or excessive crossfall on narrow hill carriageways.

Step-by-Step Solution:
Identify surface and terrain from the question.Refer to recommended camber ranges for thin bituminous layers in hills.Select the minimum value meeting drainage and safety: 3.0%.

Verification / Alternative check:
Higher cambers (e.g., 3.5%) may be used in heavy rainfall zones, but 3.0% is a widely cited minimum for thin bituminous hill roads in exam-type references.

Why Other Options Are Wrong:

• 2.2% and 2.5%: typical for bituminous surfaces in plains; may be inadequate for hills.
• 3.5%: acceptable but not the minimum requested by the question.

Common Pitfalls:

• Applying plain-terrain cambers to hill roads.
• Ignoring wheel rutting risks when cambers are too low on thin surfacings.

Final Answer:
3.0%