Pilot analysis of forces that can destabilise occupied manual wheelchairs on low-floor public transit buses.

PURPOSE: Prior to identifying optimal restraint or containment systems to prevent people using manual wheelchairs sliding or tipping on large public transit buses, the forces that destabilise them must be understood. This pilot study documented the (1) forces that wheelchairs experience on buses, (2) movement of wheelchairs on buses, and (3) differences between normal operating forces and the forces that lead to a wheelchair sliding or tipping. Methods: Data on the forces that acted on three manual wheelchairs were gathered using accelerometers across six bus routes with varied terrain. Data ranges were summarised using MATLAB, and Rainflow analysis generated graphs for visual inspection. The points at which wheelchairs began to slide, and tip were modelled and simulated in 3D in SOLIDWORKS and MSC Adams software respectively. Direct comparisons were then made between normal operating forces and the forces that lead to slide or tip. RESULTS: Real-world driving forces that act on wheelchairs under typical driving conditions ranged from -0.62 g to 0.44 g. The points at which wheelchairs began to slide or tip were documented. A table showing normal operating forces and the forces that lead to slide or tip was prepared confirming slide and tip can occur across regular manoeuvres, although such forces are rarely generated. Conclusion: These pilot data inform bus designers, operators, and transport policymakers of the forces that act on manual wheelchairs that produce slide or tip so that driver behaviour can be monitored and restraint or containment systems can be continually improved, thereby promoting safety for all passengers.