Abstract:

An adequately high static coefficient of friction between shoe and floor is necessary for pedestrian safety. In this paper, a theoretical analysis of static conditions indicates the minimum static coefficient of friction needed for prevention of pedestrian slipping on ramps while manually controlling a load. The load might be, for instance, a person on a wheelchair or gurney; freight on a trolley or pallet jack; or construction material being dragged across a sloped roof. The minimum safe coefficient is a function of ramp angle and of a weight ratio; the gross weight of the load that is being controlled, divided by the weight of the walking person (or persons) doing the controlling. The minimum static coefficient decreases with an increase in the angle (with respect to horizontal) through which force is exerted on the load, although more strength is required to control the load when the angle increases. In graphical examples provided here, the friction of the wheelchair, gurney or pallet jack is assumed to be negligible. However, the terms for non-negligible floor friction for these objects are included in the analysis. The results can aid in selecting and specifying safe flooring and footwear for use on ramps. Even when friction from the load is negligible, the analysis indicates that the present Americans with Disabilities Act-related minimum static coefficient of friction of 0.80 for ramps is not always adequate to prevent slipping accidents.