Question: A short video you once showed on high-vibration vs. smooth ground surfaces has stayed with me in all my sidewalk, patio, and outdoor assembly area design projects. I heard the U.S. Access Board has researched the effects of ground surfaces on wheelchair users. If so, can you tell us more about it and where to get the report? – Edward, Chicago

Answer: Thank you for remembering my video! Others have often commented on its value in their design projects.

Yes, in December 2014 the University of Pittsburgh’s Human Engineering Resource Laboratories released “Development of Surface Roughness Standards for Pathways Used by Wheelchair Users: Final Report.” (Download the 67-page document for free).

Researchers wanted to recommend a standard that meets ISO standard 2631-1 for mechanical vibration and shock. They gathered objective and subjective data from almost 70 wheelchair users who traveled nine engineered wooden pathways and 18 outdoor, real-world pathways. The team used accelerometers to record vibration at the seat, footrest, and backrest; then asked study subjects to rate each pathway.

The results “confirmed a high correlation between surface roughness and the whole-body vibrations (WBV) wheelchair users are exposed to, as well as the perceived comfort level of traversing the surfaces.” In some instances, vibration exceeded ISO safe levels.

Key findings shown on the report’s second page include:

There are ways to measure roadway surface roughness but none for pedestrian pathways

  • Wheelchair users are exposed to potentially harmful vibrations, the magnitude of which depends on surface characteristics
  • As surface roughness increases, vibration magnitude increases
  • As surface roughness increases, comfort ratings decrease
  • To calculate roughness, a surface profile with a resolution of 1 mm should be used
  • The profile should be filtered with a “wheelpath” algorithm with a 2.5-inch-diameter wheel
  • The roughness limit for areas less than 10 feet (such as a curb cut with low vision bubbles) should be 1.2 inches/foot
  • For areas of more than 100 feet, roughness of 0.60 inches/foot should be adopted.

The group’s future goals are to:

Work with ASTM Committee E17 to develop and approve a roughness measuring standard

  • Develop and validate a tool to measure pathway accessibility including roughness and other right-of-way features.

For more information, feel free to contact Scott Windley at (202) 272-0025 (v), (202) 272-0028 (TTY), or

I have endless horror stories of the devastating effect of cracked and broken sidewalks on the nation’s two million wheelchair users. As a wheelchair user myself, I’m making a personal plea to all of you to download this report and take it recommendations to heart. Thank you.