Transit bus injuries Incidence, biomechanics, prevention Allan Tencer, PhD University of Washington Dept of Orthopedics and Sports Medicine Occupant injury rates for different modes of transportation Average no of fatalities per 100 million miles Shaw, Gillispie, J Rehab Res and Dev, Vol. 40, No. 4, 2003, pp 309–320 Bus Collisions Goals of the Presentation Overview of bus injury type and incidence (limited to inside the bus) Explain basic biomechanics approach Describe some current research in: frontal collisions rollovers wheelchair riders non-collision injuries Overall Bus Accident Statistics (National Transit database, US DOT) Yang, Journal of Public Transportation, Vol. 10, No. 3, 2007 Injury and fatality rates/miles travelled (National Transit database, US DOT) Yang, Journal of Public Transportation, Vol. 10, No. 3, 2007 Injury and fatality rate by impact location (National Transit database, US DOT) Yang, Journal of Public Transportation, Vol. 10, No. 3, 2007 Collision factors (National Transit database, US DOT) Yang, Journal of Public Transportation, Vol. 10, No. 3, 2007 Injury and fatality rate by impact location (National Transit database, US DOT) Yang, Journal of Public Transportation, Vol. 10, No. 3, 2007 Summary of overall data A significant number of fatalities (~100 fatalities, ~4300 injuries occur yearly in buses (2002-3 data) The rate stayed constant for the ten year period (1991-2001) Front, rear, and angled collisions produce > injury rates than sideswipes or collisions with objects Most collisions occur in daylight, clear weather, on dry, straight roadways, with traffic signals Studying the detailed biomechanics is a necessary next step to reducing injury rates Definition of biomechanics Biomechanics is the study of the structure and function of biological systems by means of the methods of mechanics.” Herbert Hatze, 1974 Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. Classical mechanics is based on Newton’s three laws of motion (inertia, F=Ma, action/reaction) Seat design and frontal collision protection 1. Roadway and bus deformation analysis Mayrhofer, et al Paper 05-0351, Conf on Enhanced Safety of Vehicles, 2005 2. Modeling of the accident, assessing injuries 3. Crash simulations with dummies 4. Improving occupant safety Mechanics: Torso lifts out of seat, knees hit lower part of seat ahead, head hits upper part of seat , seat ahead bends forward, occupant rebounds back into seat Model shows how restraint use and padding of the back of the seat ahead would reduce forces on the occupant during frontal impact Relevance of the research Effect of restraint systems for highway transit buses in rollovers 1. Structural model of bus Güler, Paper Number 09-0205, Conf on Enhanced Safety of Vehicles, 2009 2. Modeling the occupants Rollover model, unrestrained Wenhui, Shengqin, 2010 Int Conf on Intelligent Computation Technology and Automation Rollover model, lapbelted Rollover 3 point restraints Enhancing occupant safety in rollovers, lap belts and side airbag Wenhui, Shengqin, 2010 Int Conf on Intelligent Computation Technology and Automation US Wheel chair related injuries, 1991-95 WC- Injuries and Deaths Total no of vehicle WC Injuries Involving Buses Involving Buses, Securement Seriously Injured Seriously Injured and Hospitalized Count % of Total 7,121 856 422 29 17 Shaw, Gillispie, J Rehab Res and Dev, Vol. 40, No. 4, 2003, pp 309–320 2.0 0.29 0.14 0.009 0.006 Wheelchair incidents aboard transit buses Count 25 4 4 Bus Mode When Incident Occurred Bus turning Sudden stop Normal operation Count 14 11 5 2 3 Result/Cause Improper securement Passenger fell from wheelchair Tie-down failed (“claw” type) Tie-down failed (“strap” type) Wheelchair failed Wheelchair restraint systems (WTORS) Restrain chair in bus and restrain occupant in chair Non collision injuries in buses Measured accelerations/decelerations of buses (Palacio,Non collision Injuries in urban buses) Accelerating from a stop Constant speed, hard braking Accelerating from a stop, then decelerating for traffic Factors affecting stability during bus motion Grip orientation Hand grip strength Shoe-floor friction coefficient Effect of hard braking on occupant motion Palacio, Non collision Injuries in urban buses Effect of bus accelerating on occupant motion Loss of grip Loss of shoe-floor contact Recommendations Bus Design and Standing Occupant Location Passengers should be discouraged from standing in the aisles. They should stand in a dedicated area opposite the stairwell and be provided with roof mounted vertical handholds. Padding in this area is important. Horizontal metal seat handles should be replaced with vertical ones hung from the roof of the bus. A lower stiffness of the rubber used for the floor should be considered. Recommendations Bus driver training Driver training should include viewing of videos based on occupant simulations of non collision accident scenarios to demonstrate the influence of driving patterns on standing occupant balance loss and subsequent injury risk. Summary Riding the bus is among the safest of transportation alternatives. The rates of occupant injury in buses has remained about the same for many years. External factors such as road and weather conditions, or angle of impact have little influence on injury rate. Detailed biomechanical studies can shed light on the specific mechanisms of injury and suggest methods to reduce injury in buses.