Superelevation is the banking of a curved roadway or ramp, tilting the surface toward the inside of the curve so a vehicle’s weight helps counter the outward force of turning.
In parking structures, superelevation applies mainly to speed ramps and helixes, where vehicles climb or descend in a continuous curve. A modest bank makes the turn feel stable at low speed, reduces tire scrub and helps drainage. Too much bank, combined with the ramp’s slope, creates an uncomfortable twist and can affect stopped vehicles.
Design considerations
- Combine superelevation and ramp slope carefully, since the resulting grade along the steepest line is greater than either alone.
- Provide smooth transitions where the bank starts and ends.
- Coordinate with drainage, so water flows to drains rather than across the travel lane.
- Account for break-over and clearance of low vehicles where slopes change.
- Follow local design standards and AASHTO principles adapted to parking speeds.
The Parkonomics view
On a helix, a little banking makes a long curve feel effortless. It is one of the details drivers never notice when it is right.
Related terms: Single Helix, Double Helix, Speed Ramp, Express Ramp, Ramp Slope