Americans with Disabilities Act Accessibility Guidelines (ADAAG) suggests certain guidelines for ramps. Basically for a 1 inch height, 1 feet (12 inches) long slop is recommended.
This makes it safe for the wheelchair user to propel oneself up or down the slope. But any slope steep than the one recommended, the user should get assistance from some one to propel him / her up or down the slope. A single ramp can be used for height upto 2 ½ feet (30 inches). If the height is more than 30 inches multiple ramps separated by flat platforms are recommended.
Basically ramps are divided into different two types:
2) Portable Ramps
The name suggests their nature. They are built using RCc or steel. Mostly, hospitals, public places, rehabilitation centers and individuals permanent residences go for permanent ramps. They are built to withstand heavy loads.
Can be transported along with the user. Detachable and / or foldable. Built using steel, fibre glass or aluminium. Portable ramps are used to eliminate heights in buildings as well as vehicles. Two basic models here are one foldable like bellows in an accordion the other come as small tracts fixed together with bolts and nuts to form the ramp. Weight is an important factor before choosing a portable ramp. Lesser the weight, the load they can withstand will also be less. Portable ramps are less expensive than permanent ramps.
Ramps can be fixed in most of the vehicles. Even trucks and public transport busses can be fixed with ramps. Basically two types are available. One that Extends from the vehicles exit and can be folded in just like bellows in an accordion and the other is fixed to the exit during the use and then can be removed and stored.
Should withstand the weight of the user along with the wheelchair and a helpmate.
Ramp should be wide enough to fit the wheelchairs width.
Using Side railings increases safety.
Wheel guards will also help in safe transition.