A study funded by the Board was recently completed on how the roughness of pathway surfaces impacts wheelchair travel. This research, which was conducted by the Human Engineering Research Laboratories at the University of Pittsburgh, assessed the impacts of bumpy and uneven surfaces on people who use wheelchairs, including power chairs, by measuring the resulting body vibrations. While there are ways to measure and analyze surface roughness for roadways, none are capable of being directly transferred to pedestrian pathways.

A sample of 76 subjects tested nine different wooden surfaces engineered to represent different degrees of roughness to collect quantitative and subjective data. In addition, a subset of 38 subjects tested a dozen existing outdoor pathways composed of brick, concrete, or asphalt. Accelerometers recorded vibrations at the seat, footrest, and backrest, and subjects completed surveys to subjectively rate each surface and to indicate whether or not it was acceptable. The results confirmed a high correlation between surface roughness and the whole body vibrations wheelchair users are exposed to, as well as the perceived comfort level of traversing the surfaces. A portion of test surfaces were rated as unacceptable by over half of the subjects and were considered to cause discomfort. Some of the existing sidewalks included in the study were also shown to cause significant vibration levels.

Based on the test results, researchers recommend sidewalk roughness index thresholds for short and long distances (1.20 inch per foot for distances up to 10 feet and 0.60 inch per foot for distances above 100 feet). They also offer recommendations for a method and protocol to measure surface roughness, including the design of a measurement device. In addition, they provide suggestions for advancing development of an industry consensus standard for sidewalk surface roughness through ASTM International.

These and other recommendations and findings are contained in a report from the study, "Development of Surface Roughness Standards for Pathways Used by Wheelchair Users: Final Report." For further information, contact Scott Windley, (202) 272-0025 (v), (202) 272-0028 (TTY), or windley@access-board.gov.