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:



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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.