A recently released study, funded by the U.S. Access Board, examines how the roughness of pathway surfaces impacts wheelchair travel.  The research, conducted by the Human Engineering Research Laboratories at the University of Pittsburgh, assesses the impacts of bumpy and uneven surfaces on people who use wheelchairs, including power chairs, by measuring the resulting body vibrations.

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.  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).