These are the A.D.A. Accessibility
Guidelines Pertaining to Ground and Floor Surfaces (Appendix 4.5.1)
People who have difficulty walking or maintaining
balance or who use crutches, canes, or walkers, and those with restricted
gaits are particularly sensitive to slipping and tripping hazards.
For such people, a stable and regular surface is necessary for safe walking,
particularly on stairs. Wheelchairs can be propelled most easily
on surfaces that are hard, stable, and regular. Soft loose surfaces
such as shag carpet, loose sand or gravel, wet clay, and irregular surfaces
such as cobblestones can significantly impede wheelchair movement.
Slip resistance is based on the frictional
force necessary to keep a shoe heel or crutch tip from slipping on a walking
surface under conditions likely to be found on the surface. While
the dynamic coefficient of friction during walking varies in a complex
and non-uniform way, the static coefficient of friction, which can be measured
in several ways, provides a close approximation of the slip resistance
of a surface. Contrary to popular belief, some slippage is necessary
to walking, especially for persons with restricted gaits; a truly "non-slip"
surface could not be negotiated.
The Occupational Safety and Health Administration
recommends that walking surfaces have a static coefficient of friction
of "0.5". A research project sponsored by the Architectural and Transportation
Barriers Compliance Board (Access Board) conducted tests with persons with
disabilities and concluded that a higher coefficient of friction was needed
by such persons. A static coefficient of friction of "0.6" is recommended
for accessible routes and "0.8" for ramps.
It is recognized that the coefficient of
friction varies considerably due to the presence of contaminants, water,
floor finishes, and other factors not under the control of the designer
or builder and not subject to design and construction guidelines and that
compliance would be difficult to measure on the building site. Nevertheless,
many common building materials suitable for flooring are now labeled with
information on the static coefficient of friction. While it may not
be possible to compare one product directly with another, or to guarantee
a constant measure, builders and designers are encouraged to specify materials
with appropriate values. As more products include information on
slip resistance, improved uniformity in measurement and specification is
likely. The Access Board's advisory guidelines on Slip Resistant
Surfaces provides additional information on this subject.