A common question to ask when considering a portable wheelchair ramp is how long must the ramp be to achieve a safe, practical angle? The Americans with Disabilities Act Standards partially answers this question by stating that a ramp's maximum incline should be no greater than a 1:12 gradient, approximately a 5-degree angle (12" of ramp for every 1" of rise). It should be noted that this is a "public" standard that epitomizes safety and function, but may not be realistic in private residences and vehicles where size and economic restrictions apply. It is, however, the ideal standard for those who must propel their own wheelchair up a ramp.
Powerchair users and assisted manual wheelchair users may require a shorter ramp to cover a given rise, as with a van ramp. While safety decreases with increases in angle, a user still may be able to negotiate a steeper ramp than ADA ideals if their abilities and environmental conditions permit. For a 1-foot rise, for example, the ADA standard of 1:12 dictates a 12-feet long ramp. However, if a user assumes a 2:12 slope, building a 6-feet long ramp, approximately a 9.5-degree angle occurs. Now, this is a fairly steep angle, but, again, based on one's abilities, wheelchair performance, and environmental conditions, such an angle still may be usable.
Ramp angles over 10-degrees should be avoided. Stability, traction, and directional control become tremendously reduced. Some powerchairs may climb a greater than a 10-degree angle, but don't confuse capability with safety, as just because a powerchair will climb such extreme angles, doesn't mean it's safe.
Ramp Widths
In conjunction with ramp angles, ramp widths are vital to ramp use and safety. The wider the ramp in comparison to one's wheelchair, the easier and safer the ramp is to negotiate. Attempting to use a 25.5"-wide powerchair on a 26"-wide ramp won't leave enough room for safe steering. However, a 30"-wide ramp would offer enough space on each side of the wheels for a skilled user to negotiate the ramp with a 25.5"-wide wheelchair.
Two-piece "track ramps" (a pair of narrow ramps, one for each side of a wheelchair's wheels), require additional width considerations. Because track ramps require that a wheelchair's wheels fit inside a narrow channel on each side, the combined linear width of the front and rear wheels is vital. If a track ramp's channel width is 8", but
your drive wheels are 4"-wide, with 2"-wide casters, that sit 2" inward of the drive wheels (that is, the casters are narrower on the wheelchair than the drive wheels), your wheelchair may not function well on track ramps. The ideal, then, for track ramps is to have a wheelchair where the front and rear wheels align.
Portable Ramp Folding Styles
The key to portability is whether a ramp can be easily transported, so ramps come in a variety of storable forms.
Single-fold ramps retain their length, but fold in half, resulting in a 6'x30" ramp folding to 6'x15".
Multi-fold ramps, also called suitcase ramps, fold several directions, allowing a 6'x30" ramp to fold to 3'x30".
Telescoping track ramps slide into themselves, often reducing their lengths to one-third for transport.
Roll-up ramps feature rigid side members that can be removed so that the jointed center surface can roll up (though, these ramps can be difficult to assemble and disassemble).
Many users prefer multi-fold ramps above other forms because they allow a strong, compact system that is quickly usable.
Mounting Styles
For regular use in a specific environment, most portable ramps feature mounting points atop the threshold point. Commonly, these points are holes, to which adjoining posts or clips are mounted on a van door's threshold, thereby securing the ramp during use. Additionally, several portable ramp manufacturers offer semi-permanent installation brackets for vans so that the ramp is folded into the doorway, eliminating the need for additional stowage.