Transit bus injuriesIncidence, biomechanics, prevention

Allan Tencer, PhDUniversity of Washington

Dept of Orthopedics and Sports Medicine

Occupant injury rates for different modes of transportation

Shaw, Gillispie, J Rehab Res and Dev, Vol. 40, No. 4, 2003, pp 309–320

Average no of fatalities per 100 million miles

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 protection1. 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

WC- Injuries and Deaths Count % of Total

Total no of vehicle WC Injuries 7,121 2.0 Involving Buses 856 0.29Involving Buses, Securement 422 0.14Seriously Injured 29 0.009Seriously Injured and Hospitalized 17 0.006

Shaw, Gillispie, J Rehab Res and Dev, Vol. 40, No. 4, 2003, pp 309–320

US Wheel chair related injuries, 1991-95

Wheelchair incidents aboard transit buses

Count Bus Mode When Incident Occurred25 Bus turning4 Sudden stop4 Normal operation

Count Result/Cause14 Improper securement11 Passenger fell from wheelchair5 Tie-down failed (“claw” type)2 Tie-down failed (“strap” type)3 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)

Constant speed, hard braking

Accelerating from a stop

Accelerating from a stop, then decelerating for traffic

Factors affecting stability during bus motion

Grip orientationHand grip strengthShoe-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 gripLoss of shoe-floor contact

RecommendationsBus 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.

RecommendationsBus 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.

SummaryRiding 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.