Ramp Fall Prevention

USE OF RAMPS AS WALKING SURFACES

When sloped ground must be utilized as a walking surface, the use of a ramped surface can, under certain circumstances, have advantages over the selection of a stepped surface. However, when a ramp is selected, special attention must be given to providing ramp design features that properly control inherent hazards of ramp use; that is, special attention must be given to providing a safe ramp slope and a ramp surface that is highly slip resistant, especially if such surfaces are subject to moisture or other contaminants.

The design of ramps with gradual slopes, the provision of a high coefficient of ramp surface friction, appropriate use of handrails, and the reduced walking stride intuitively used by ramp users, can combine to make ramps an attractive alternative for the safe transfer of persons from one level to another in architectural settings. Ramps that do not meet safe design criteria, however, can be a source of unacceptable risk to ramp users.

Slip Resistance of Ramp Surfaces. Special attention must be given to providing and maintaining a high surface coefficient of friction on ramp surfaces. A non-skid surface should be provided on all ramps, regardless of slope. The slightest slope in a walking surface will increase the risk of foot slip if there is not a corresponding increase in slip resistance. The reason for this is derived from a recognition of the change in forces exerted on the surface during ramp use compared to the forces present during level surface walking. During ramp ascent, a higher (downramp) horizontal force is exerted by the trailing leg as pressure is exerted against the ramp surface to move the body forward and up the ramp. During ramp descent, a higher (downramp) horizontal force is exerted by the leading foot (shoe heel) as it initially contacts the ramp surface. These factors dictate a high coefficient of ramp surface friction to prevent slipping and the potential falls associated with ramp use. Should a sloped surface have friction characteristics at or near the minimum acceptable level of friction for a level surface, the increased (downward) force exerted on the surface during the walking process can result in a slip and potential fall.

Recommended Ramp Slope. The least possible slope should be used for any ramp. According to the Human Factors Design Handbook (Woodson, 1981), where space allows, a ramp slope of 1:20 or a 5 percent slope (2.86 degrees) is recommended. When the slope becomes greater, it is very taxing for most wheelchair users to "pull the hill." Thus this upper limit is a preferred slope guideline for all ramps. Although healthy, non-handicapped individuals can negotiate fairly steep (high slip resistant surfaced industrial) ramps up to 15 degrees (27 percent slope or a slope of 1:3.7), the main criteria for designing most ramps should be based on the needs of the average user, including the elderly and the disabled. While recommending a maximum ramp slope of 1:20 or 2.86 percent, this reference states that no (public) ramp should exceed about 8 percent slope (1:12 slope or 4.76 degrees) under any circumstances.

ANSI A117.1-1986 recommends that the least possible slope be used for any ramp, limiting the maximum slope of a ramp to 1:12 (1 inch rise for every 12 inches of run), equaling a percent slope of 8.33 (the decimal equivalent of slope times 100 equals percent slope) or an incline of 4.7 degrees (arc-tangent of slope equals degrees).

The Standard Building Code (1988) and the Uniform Building Code (1988) also require that ramps for the physically handicapped not exceed a slope of 1:12 (4.7 degrees), and do not allow any ramp to exceed 1:8 (7.1 degrees).

The Life Safety Code allows some classes of ramps to have a slope as steep as 1:8 (7.1 degrees). Both the Life Safety Code and the National Safety Council recommend that ramp slopes do not exceed 7 degrees.