Camber shape effect: On a pavement with a parabolic camber, how does the angle of inclination (cross slope) of vehicles vary from the crown to the edges?
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AMore at the crown
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BLess at the edges
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CMore at the edges
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DSame at the edges as well as at the crown
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ENone of these
Answer
Correct Answer: More at the edges
Explanation
Introduction / Context:Camber (cross fall) shapes the transverse slope of a road to drain water. A popular shape is a true (quadratic) parabolic camber, which avoids abrupt slope changes and improves riding comfort compared to a straight-line (plane) camber.
Given Data / Assumptions:
- Parabolic camber profile across the carriageway.
- Angle of inclination refers to the local cross slope at a given offset from the crown.
Concept / Approach:
In a parabolic camber, the slope is zero at the crown and increases with distance from the centerline, reaching its maximum at the pavement edges. This yields gentle near-crown slopes to enhance comfort and larger edge slopes to provide drainage capacity.
Step-by-Step Reasoning:
Parabolic profile y = kx^2 (measured from crown).Local slope dy/dx = 2kx → increases linearly with x.Hence, slope is smallest near crown and largest at edges → vehicles are more inclined at edges.Verification / Alternative check:
Camber tables show edge slopes equal to the specified camber percentage, while slope at the crown is effectively zero for a parabolic form.
Why Other Options Are Wrong:
- “More at the crown” or “Less at the edges” contradict the mathematics of a parabola.
- “Same at edges and crown” applies to plane camber, not parabolic.
Common Pitfalls:
- Assuming a uniform cross slope for all camber shapes; only straight-line camber has constant slope.
Final Answer:
More at the edges.