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DATE: September 13, 2004

Injuries due to mismatch crashes support need for vehicle redesign

While the number of fatalities resulting from crashes between passenger vehicles decreased steadily between 1980 and 1998, there has been an increase in fatalities resulting from collisions between passenger vehicles and light trucks, a category that includes sport utility vehicles, pickup trucks and vans. The patterns of injuries that occur in these collisions suggest a need to redesign both types of vehicles, according to new research by investigators at the Harborview Injury Prevention & Research Center (HIPRC).

“Vehicle Mismatch: Injury Patterns and Severity” is published in the September issue of Accident Analysis and Prevention.

The researchers reviewed cases of vehicle mismatch collisions in the Seattle Crash Injury Research and Engineering (CIREN) database. Vehicle mismatch is defined as design differences between types of vehicles (e.g., weight, frame height and stiffness) that result in disproportionate damage patterns when different vehicles collide.

Of the cases they reviewed, 32 collisions of mismatched vehicles involved 41 injured vehicle occupants. Crashes were reviewed by type of collision (e.g., front or side impact) and the vehicles of the injured occupants.

For side-impact crashes to passenger vehicles, injuries to the head and upper chest occurred frequently due to contact by light-truck bumpers above the passenger vehicle's side-door reinforcement. In cases of front impact to the passenger vehicle, the light truck's bumper frame overrode the car's bumper frame, causing head and chest injuries, as well as multiple leg fractures due to the occupants' contact with the steering column and instrument panel. When a passenger vehicle collided with a light truck, override resulted in leg fractures to the passenger vehicle's occupants, due to intrusion of the toe pan into the passenger area.

The researchers found definite patterns of injury for each type of vehicle mismatch, with 10 occupants in passenger vehicles dying after collisions with light trucks, compared to no deaths among the light-truck occupants. These findings are similar to death-risk results in a study by the Insurance Institute of Highway Safety (IIHA). The IIHA has reported that passenger vehicle occupants are 3-4 times more likely to die than light-truck occupants in frontal crashes between the two types of vehicles, and at 27-48 times greater risk of death after side-impact crashes.

Design improvements to both types of vehicle can improve the chances of surviving these crashes, the researchers say. A lower, reinforced bumper in light trucks would apply the impact to a passenger vehicle's strong frame, rather than to its weak grill. This would minimize intrusion into the passenger area of the car, as well as reduce toe intrusion into the light truck, lessening the risk of those occupants incurring leg fractures. Side airbags with head and chest protection could protect occupants of passenger vehicles during side-impact crashes. Extending side-panel reinforcement to cover the entire door would reduce intrusion during impact, thus reducing the risk of injury.

“Our research shows that definite injury patterns arise from vehicle mismatch in side-impact and frontal collisions,” says Dr. Stephanie Acierno, a Robert Wood Johnson clinical scholar at the University of Washington (UW) and principal investigator of the study. “With increasing numbers of SUVs and other light trucks on the road, design improvements to these vehicles, as well as to passenger cars, must be considered.”

In addition to Acierno, the study was conducted by Rob Kaufman, CIREN crash reconstructionist based at the Harborview Injury Prevention & Research Center; Dr. Fred Rivara, a UW professor of pediatrics and adjunct professor of epidemiology; Dr. David Grossman, a UW professor health services and adjunct professor pediatrics; and Dr. Charles Mock, a UW associate professor of surgery.