Laws regarding wheelchair ramp accessibility vary by area, but the standard guidelines state that all government buildings and places of business constructed after 1992 must have an accessible wheelchair ramp. The Americans With Disabilities Act defines a ramp as at minimum 1 inch of incline per 20 inches of length.
Ideally, wheelchair ramps are built at a ratio of 1 inch of incline per 12 inches of length. Ramps must have no more than 30 inches of rise and must feature the lowest practical amount of slope. Ramps over 6 inches high or 72 inches long must feature handrails that are between 34 and 38 inches in height. Ramps can be no less than 36 inches wide with a landing of no less than 60 inches, and there must be an additional 60 inches of landing for every section where the ramp changes direction.
There must also be landings at both the top and bottom of the ramp. Ramps that are located outdoors must be slip-resistant and designed in a manner that prevents rainfall from accumulating on the surface of the ramp. Ramps with drop-offs must include curbs or other projection surfaces to prevent users from slipping off the ramp.