Break-Over Angle and Ramp Transitions

Break-over angle is the steepest crest a vehicle can drive over without its underside touching the ground between the front and rear wheels.

Where two slopes meet at a crest, a low car can high-center. The break-over angle sets how abrupt that transition may be, which is why ramps blend grade changes rather than kinking sharply.

It depends on wheelbase and ground clearance: long, low vehicles have small break-over angles. In a parking structure it matters wherever a ramp meets a flat floor at the top. If the change in slope is too abrupt, cars scrape. Designers solve this with transition sections, short lengths of ramp at an intermediate slope, and check them against a design vehicle.

Related angles

Approach angle: the steepest slope a vehicle can climb onto without the front bumper hitting.
Departure angle: the same at the rear.
At the bottom of a ramp, the approach and departure angles govern; at the top, the break-over angle does.

Design practice

Provide transition slopes, often about half the main ramp slope, where slope changes sharply. See ramp slope.
Check low sports cars and long-wheelbase vans and pickups.
Use swept-path and profile software to check transitions. See AutoTURN.

The Parkonomics view

A scraped bumper is a design flaw the customer hears. Transitions take a little extra length, and they are worth it.