New Research Examines Effects of Cross Slope on Wheelchair Travel

From the US Access Board:

Various factors affect the accessibility of outdoor surfaces, among them firmness, stability, smoothness, slope, and weather conditions.  Surface slopes that run perpendicular to the direction of travel, often referred to as the cross slope, have been identified as a key factor in usability according to several human factor studies involving people who use manual wheelchairs.  The Board has initiated further investigation into the impact of cross slope on wheelchair travel through a project undertaken by the Human Engineering Research Laboratory (HERL) at the University of Pittsburgh. 

Under this project, investigators reviewed existing research and surveyed people who use wheelchairs to gain insight into this issue, including the interaction of slope, surface, and weather conditions on wheelchair travel.  Based on the information collected, researchers developed a protocol for a follow-on human factors study to be undertaken at HERL facilities with additional support from the Veterans Administration and Paralyzed Veterans of America.

In the Board's preliminary project, researchers found that while studies show that cross slopes make wheelchair travel more difficult, there was little consensus on methods or protocols for measuring these effects.  Further, they determined that the measures used in most studies, such as energy consumption and perceived effort, cannot fully assess the complex effects of cross slope.  Few studies were found that investigated wheelchair propulsion in outdoor environments over a range of surfaces.  Results from the project survey confirmed that terrain features interact in complex ways and that the effects are more pronounced among certain populations.  Findings suggest that older adults, women, and people with progressive conditions, such as multiple sclerosis, or upper extremity impairment are most likely to experience difficulty negotiating cross slopes.  This can be further aggravated by wheelchair design, such as configurations enhancing rearward stability.    

Based on the results of the Board study, the project team developed a protocol to measure the effects of cross slope using a cross sectional group of test subjects.  Testing is currently underway on a range of cross slopes, running slopes, and surface conditions, including those that are smooth, irregular, and slippery.  Devices developed by HERL to measure work, energy, distance-per-stroke, and pushrim forces are being used to capture data.  Results of this research, including the preliminary study, will be posted on the Board's website once published.  For further information, contact Lois Thibault, the Board's Research Coordinator, at thibault@access-board.gov.