Highway camber calculation: A pavement 9 m wide has the crown 15 cm higher than each edge. Compute the camber (slope from crown to edge) and select the correct 1-in-N value.

Introduction / Context:
Camber (also called crossfall) is provided on roads so that rainwater drains quickly from the crown to the edges. This problem checks your ability to compute the camber when the crown-to-edge level difference and pavement width are known.

Given Data / Assumptions:

• Total pavement width = 9 m.
• Height difference between crown and one edge = 15 cm = 0.15 m.
• Camber is defined along half-width (from crown to one edge).
• Uniform straight-line crossfall on each side of the crown.

Concept / Approach:
Camber (slope) = rise / run. For a crowned section, the run is the half-width from crown to edge. Convert the rise to metres and express the final answer as a ratio 1-in-N.

Step-by-Step Solution:

Verification / Alternative check:
Convert to percentage: 0.03333 * 100 ≈ 3.33%. This is a typical camber magnitude for bituminous or WBM surfaces, confirming reasonableness.

Why Other Options Are Wrong:
1 in 60 and 1 in 45 are milder than the computed slope; 1 in 15 and 1 in 7.5 are steeper than required.

Common Pitfalls:
Using the full pavement width (9 m) instead of half-width; forgetting to convert centimetres to metres; confusing percent slope with the 1-in-N form.

Final Answer:
1 in 30