Wheelchair ramps and all other accessible threshold regulations are defined by the Americans with Disabilities Act (ADA), with a full listing of building accessibility guidelines laid out by the United States Access Board. Regulations address the physical properties of ramps, safety features and the definition of what counts as a wheelchair ramp in the first place.
According to the ADA, a ramp is defined as any part of an accessible route with a slope greater than 1:20. This not only applies to stair alternatives, but also to curbs and paved inclines. A ramp is also defined according to measurements of slope and rise. Slope is the angle at which the ramp is set from bottom to top, and rise is the height one achieves by going up the ramp.
Wheelchair ramps that fit the ADA regulations should have a slope of at least 1:12 ratio, meaning that for every 12 inches travelled, the wheelchair user gains 1 inch of height. The only exception to this is that a wheelchair ramp can have a slope between 1:8 and 1:10 ratio, but only if the rise is less than 3 inches. The ramp should also have a width of at least 36 inches to provide wheelchair clearance. For every 30 feet in a ramp, there must be a landing 60 inches square to provide proper turning clearance.
Any wheelchair ramp achieving anything higher than a 6-inch rise or 6 feet in length must have a handrail on either side. These handrails must be within 34 to 38 inches high from the ramp floor. To avoid water accumulation that could lead to wheelchair slippage, proper drainage must be provided or water protection such as canopies or heating units to remove snow and ice.
Types of Ramps
A portable ramp is a modular, telescoping or folding ramp designed for use in multiple entryways and access areas. Modular ramps are defined as those allowing customised orientation and placement, often fitted together with bolts and clamps. Vehicle ramps allow wheelchair access to buses, vans and trucks for transportation purposes. All ramps must have stable platforms and a flush transition from the ramp to the threshold.