firmness and stability testing
why ASTM F1951
The Americans with Disabilities Act Accessibility Guidelines (ADAAG) specify that accessible routes must have ground and floor surfaces that are firm and stable. Surfaces that are not firm and stable limit accessibility for wheelchair, cane, crutch, and walker users, parents with strollers, and other individuals with mobility limitations.
Firm and stable definitions are subjective, however, and require a more objective standard by which to measure a surface. A consistent and objective testing method is required in order to adequately assess the quality of a surface.
The ASTM F1951 Wheelchair Work Measurement Method was originally designed to provide a systematic and consistent means of measuring the characteristics of a surface and its capability of providing access to playgrounds.
A test rehabilitation wheelchair with pneumatic rear tires and front wheels is used to measure the average work per foot (work per meter) values for straight propulsion and for turning on a test surface. Forces applied to the pushrims are measured and used to calculate the work per foot (per meter) value for each trial. These values are then compared to the average work per foot (work per meter) values for straight propulsion and for turning on a hard, smooth surface with a grade of 7.1%. Surfaces with work per foot (per meter) values at or below the measures taken for a surface at 7.1% are classified as accessible. Other test specifications are also established in the ASTM F1951 standard.
Starting from a stationary position with the wheelchair casters in the trailing position, the test wheelchair rider propels the wheelchair in a straight path across the test surface a distance of 6.56 ft (2 m) using four uniform pushes within 7 seconds.
If the force required to push the wheelchair straight across the test surface is less than or equal to the force required to push the same wheelchair straight across an uphill 7.1% ramp, the surface is accessible.
Starting from a stationary position with the wheelchair casters in the trailing position, the test wheelchair rider propels the wheelchair on the test surface around a turn guide using four uniform pushes on the pushrim of the outside wheel until the wheelchair is oriented within 90° from the starting position. The test is performed within 7 seconds.
If the force required to push the wheelchair around the turn guide on the test surface is less than or equal to the force required to push the same wheelchair around the same turn on an uphill 7.1% ramp, the surface is accessible.