What does the term superelevation refer to in highway design?

Superelevation refers specifically to the banking of a roadway at a curve designed to counteract the effects of centrifugal force acting on vehicles traversing that curve. As vehicles navigate the curve, they experience a lateral force that can cause them to slide outward if not properly balanced. By introducing a superelevated cross-section to the curve—where the outer edge of the road is raised higher than the inner edge—engineers help to balance these forces, allowing vehicles to maintain their path without skidding. This design feature is crucial for ensuring safety and enhancing the performance of the road, especially at higher speeds.

The other options do not accurately represent the concept of superelevation. The increase in a road's elevation above sea level refers to a general measure of elevation that is unrelated to the geometric design of curves. Measuring surface roughness pertains to different aspects of pavement quality, and adjusting road alignment focuses more broadly on alignment corrections that improve safety, rather than specifically addressing the forces experienced in a curve. Superelevation is unique in its direct relation to vehicle dynamics on curved segments of highways.