935 JRRD JRRD Volume 49, Number 6, 2012 Pages 935–948 Investigation of wheelchair instability during transport in large accessible transit vehicles Zdravko Salipur, MEng; Karen Frost, PhD; Gina Bertocci, PhD, PE * Injury Risk Assessment and Prevention (iRAP) Laboratory, Mechanical Engineering Department, J. B. Speed School of Engineering, University of Louisville, Louisville, KY Abstract—Large accessible transit vehicles (LATVs, fixed- route intracity buses), generally considered safe, may not be as safe for wheelchair-seated passengers. Transit provider prac- tices vary regarding use of wheelchair tiedown and occupant restraint systems (WTORSs), while recent research suggests high levels of WTORS disuse and misuse. We sought to better understand wheelchair and wheelchair passenger instabilities related to WTORS disuse and misuse on LATVs. This article presents a retrospective review of 295 video surveillance records of wheelchair passenger trips on LATVs. Wheelchair trips involving disuse and misuse of WTORS were quantified and categorized based on WTORS configurations. Cases of wheelchair and wheelchair passenger instability were catego- rized based on severity, type, and direction. Three adverse events involving severe wheelchair and/or passenger instability were examined in greater detail. Results showed 20.3% of records involved wheelchair-related adverse events (95% minor instabilities, 5% severe instabilities). Scooters were most likely to be unstable, followed by manual and power wheelchairs. In most instability cases, no tiedowns were used to secure the wheelchair and no lap belt was used to restrain the wheelchair passenger properly. In many instances, the lap belt was misused in an attempt to secure the wheelchair, whereas the shoulder belt was never used. Key words: Americans with Disabilities Act, fixed-route intra- city bus, instability, large accessible transit vehicle, public tran- sit, wheelchair instability, wheelchair safety, wheelchair securement, wheelchair tiedown and occupant restraint system, wheelchair transportation. INTRODUCTION Large accessible transit vehicles (LATVs), commonly known as fixed-route intracity buses, are generally consid- ered a safe mode of transportation with a low fatality inci- dence of all passengers [1]. This is in part because of overall LATV mass and the slow speed of travel associated with intracity routes. Despite this relatively safe environ- ment, Shaw and Gillispie found that wheelchair passen- gers have an accident rate over 350 times greater than that of non-wheelchair-using passengers [2]. Shaw estimated that the ratio of wheelchair passenger injury claims rela- tive to the wheelchair passenger population is much higher than the claims ratio for the general population, indicating a higher likelihood for wheelchair passengers to incur inju- ries [3]. The U.S. National Highway Transportation Safety Administration reported that 35 percent of injuries and deaths that occurred between 1990 and 1995 involving Abbreviations: ADA = Americans with Disabilities Act, CG = center of gravity, ISO = International Organization for Stan- dardization, LATV = large accessible transit vehicle, NIDRR = National Institute on Disability and Rehabilitation Research, ORS = occupant restraint system, WoFT = Wheelchairs on Fixed-Route Transit, WTORS = wheelchair tiedown and occu- pant restraint system. * Address all correspondence to Gina Bertocci, PhD, PE; University of Louisville, Research Tower, Room 204, 500 S. Preston St, Louisville, KY 40202; 502-852-0296; fax: 502- 852-6053. Email: g.bertocci@louisville.edu http://dx.doi.org/10.1682/JRRD.2011.06.0098