Jonathan Duvall

Development of Surface Roughness Standards for Pathways Used by Wheelchairs

More than 2 million people in the United States use a wheelchair for mobility. These Americans not only rely on their assistive technology to complete simple, daily tasks, but they also depend on functional and accessible sidewalks to do so. Although the Americans with Disabilities Act Accessibility Guidelines established by the Access Board provide suggestions for pathways, they are subjective and not measurable. This ambiguity results in public pathways with many bumps and cracks, which can lead to harmful whole body vibrations (WBVs) for wheelchair users. WBVs with a root mean squared (RMS) value greater than 1.6 m/s2 for more than a 1-h period may result in back and neck pain or muscle fatigue. For the development of a standard for surface roughness, subjective and objective information needs to be gathered and analyzed. Sixty-one subjects were recruited to travel over nine simulated wooden surfaces with varying roughnesses that were modeled after outdoor surfaces. A subset of the subjects also traveled over six outdoor surfaces. With the use of their own chairs, subjects traveled over each surface while accelerometers recorded vibrations at the seat, footrest, and backrest. After they traveled over each surface, subjects were asked to fill out a short questionnaire on the acceptability of each surface. The vibrations were converted to RMS accelerations. Both RMS accelerations and subject surface ratings were compared with surface roughness. As surface roughness increased, RMS accelerations increased, and subject surface ratings decreased. Some surfaces generated RMS accelerations above the 1.6 m/s2 threshold; this result suggested that some sidewalks caused harmful vibrations to wheelchair users.

Pedestrian Pathway Characteristics and Their Implications on Wheelchair Users

Individuals who use wheelchairs (WCs) frequently navigate over pathways with obstacles (e.g., bumps or curb descents) or terrain that is extremely rough. Surface characteristics such as roughness can have an effect on comfort and variables associated with bodily injury. Understanding these relationships can be helpful to ensure safe and comfortable access to all public and private pathways. This article reviews existing research related to the topics of surface roughness effects on WC users bodies, surface roughness measurement techniques, and design guidelines and exposure limits that attempt to ensure pathways are safe and passable. These findings are discussed along with opportunities to improve them. Using a broad literature search, it was found that several measurement and analysis techniques exist to characterize surface roughness related to automobile roadways, but they have not been systematically applied to WC use over pedestrian pathways. The roughness measurement approach that appears most relevant and adaptable for sidewalks are rolling profilers. Commercially available devices could be recalibrated or adapted to measure pedestrian pathways. IRI and ride-quality analysis techniques appear most relevant and could also be adapted. Any analysis technique that uses profiles of surfaces should focus on frequencies and wavelengths that are most applicable to WC riders.

Development of Route Accessibility Index to Support Wayfinding for People with Disabilities

Wayfinding is a common task routinely performed by people traveling between unfamiliar locations, but can be a challenge for people with disabilities. In order to be able to travel safely and comfortably, people with physical disabilities depend on the accessibility of the built environment. It is through these accessibility elements that people who use wheelchairs can find their ways in unfamiliar environments. When used by people with disabilities, wayfinding and navigation services must contain accessibility data and support functions to utilize this data. However, while there are standards, such as the Americans with Disabilities Act Accessibility Guidelines, upon which accessibility data can be based or derived, currently there is no automated metric for evaluating the level of accessibility for pathways. To fill this gap, this paper proposes a Route Accessibility Index as a metric for evaluating a pathway’s accessibility and discusses its value in a wayfinding case study.

Design and focus group evaluation of a bed-integrated weight measurement system for wheelchair users

ABSTRACT Regular weight monitoring is known to help with weight management, which is an important part of maintaining a healthy, active lifestyle. Unfortunately, weight monitoring is challenging for wheelchair users because the few scales that are available are expensive and very large. Consequently, wheelchair users typically learn their weight at infrequent visits to their healthcare providers, which likely contributes to higher prevalence of obesity-related health risks among this population. In this article, we describe the design and development of the Embedded Scale, or E-Scale, which is a bed-integrated bodyweight measuring system that allows a user to measure and track their weight. The E-Scale team followed a standard product development approach to build the E-Scale prototype. Bench testing results indicate that the performance of the prototype is on par with commercially available wheelchair scales (capacity = 1,200 lbs, accuracy = 1.73 lbs, and precision = ± 0.35 lbs over one-fourth rated capacity). Institutional Review Board (IRB)-approved focus groups with 20 Veterans who use wheelchairs for mobility were conducted to gather feedback about the design, which was very positive. Development and testing results suggests the E-Scale technology is feasible and may provide a valuable tool to help wheelchair users manage their weight.

Proposed pedestrian pathway roughness thresholds to ensure safety and comfort for wheelchair users

ABSTRACT In the United States, over three million people use a wheelchair for their primary means of mobility and they rely on functional and accessible pathways to participate in their communities. The Americans with Disabilities Act Accessibility Guidelines related to pathway roughness are currently ambiguous, subjective and therefore unable to be measured. Consequently, many public pathways are sufficiently rough to result in harmful vibrations and discomfort for wheelchair users. In previous research, subjective ratings and root-mean-square accelerations were reported from subjects traveling over surfaces with various roughnesses in their own wheelchairs. The purpose of the current study is to use previous data to propose roughness thresholds by correlating the roughness of surfaces to vibration data and subjective ratings from wheelchair users. The results suggest a pathway roughness index threshold of ≤50 mm/m (1.2 in./ft) for a surface segment of 100 m (328 ft) in length, and ≤100 mm/m (1.2 in./ft) for a surface segment of 3 m (9.8 ft) in length would protect wheelchair users against discomfort and possible health risks due to vibration exposure. For surfaces of different lengths, a 3 m (9.8 ft) and 100 m (328 ft) moving window should be used.