Vehicle mismatch: injury patterns and severity

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Abstract

Light truck vehicles (LTV) are becoming more popular on US highways. This creates greater opportunity for collisions with passenger vehicles (PV). The mismatch in weight, stiffness, and height between LTV and PV has been surmised to result in increased fatalities among PV occupants when their vehicles collide with LTV. We reviewed cases of vehicle mismatch collisions in the Seattle Crash Injury Research and Engineering Network (CIREN) database to establish patterns and source of injury. Of the first 200 Seattle CIREN cases reviewed, 32 collisions with 41 occupant cases were found to involve LTV versus PV. The cases were reviewed by type of collision and vehicle of injured occupant: side impact of PV with LTV, front impact of PV with LTV, and front impact of LTV with PV.

For each type of crash, injury patterns and mechanisms were identified. For side impact to PV, head and upper thorax injuries were frequently encountered due to LTV bumper frame contact above the PV side door reinforcement. For frontal impact to PV, severe multiple extremity fractures along with some head and chest injuries were caused by intrusion of the instrument panel and steering column due to bumper frame override of the LTV. Underriding of the PV when colliding with the LTV resulted in severe lower extremity fractures of the LTV occupant due to intrusion of the toe pan into the vehicle compartment of the LTV.

The injuries and the sources identified in this case series support the need for re-designing both LTV and PV to improve vehicle compatibility. Revising Federal Motor Vehicle Safety Standard 214 to reinforce the entire door, consider adding side airbags, and re-engineering LTV bumpers and/or frame heights and PV front ends are possible ways to reduce these injuries and deaths by making the vehicles more compatible.

Introduction

From 1980 to 1998, there was a steady decrease in the number of fatalities resulting from passenger vehicle (PV) versus PV collisions (Lombardo, 2001). However, since 1980, there has also been an increase in fatalities resulting from the collision of PV and light truck vehicles (LTV). LTV include sport utility vehicles (SUV), pickup trucks, and vans which are constructed on a truck frame. This increase is surmised to be due to the mismatch between the PV and LTV and the increasing representation of LTV in the vehicle fleet.

Vehicle mismatch is defined as design differences between vehicle types which result in disproportionate damage patterns to the vehicles involved in a collision; these design differences include weight, frame height, and stiffness. This is also known as crash incompatibility (IIHS, 1999). The damage patterns can result in a violation of the structural integrity of the passenger compartment resulting in increased risk of serious injury or death to the occupants. Studies by the Insurance Institute of Highway Safety (IIHS) have shown that the relative risk of death for occupants of PV involved in frontal collisions with LTV is 3–4 times greater than those involved in similar collisions with another PV. For side impacts, the relative risk of death can be 27–48 times greater for the occupants of the PV (IIHS, 1999).

LTV are becoming more common on our highways. For the year 2000, Motor vehicle registrations show 77.8 million light trucks in the US, a 63.8% increase from 1990. During the same period, there was a 1% decrease in the number of registered PV. LTV now represent 40% of all registered motor vehicles (Office of Highway Policy Information, 2000) and the LTV market share has increased from 14.2% in 1996 to 21% in 2000 (Polk, 2001). If these trends continue, LTV will soon become the majority of vehicles on the road, resulting in even greater occurrences of vehicle mismatch.

The Crash Injury Research and Engineering Network (CIREN) was developed under the National Highway Traffic Safety Administration (NHTSA) to provide detailed crash site analysis and specific occupant injury data to improve the prevention, treatment, and rehabilitation of motor vehicle crash injuries. The purpose of the current study is to examine crashes with vehicle mismatch to determine the kinematic mechanisms of occupant injury and identify possible design improvements to reduce fatalities and prevent severe injury.

Section snippets

CIREN database and case selection

The Harborview Injury Prevention and Research Center (HIPRC) is one of 10 CIREN centers. Inclusion criteria for the CIREN database include: (1) the vehicle can not roll nor can the occupant have been ejected from the vehicle, (2) the case occupants must have been restrained or have an airbag deploy, have sustained at least one injury with abbreviated injury severity score (AIS)≥3, and have been in a vehicle manufactured within the last 6 years. For each enrolled crash the following data were

Side impact collisions

Table 1 displays the crash data for PV involved in side impact collisions with LTV. Fourteen collisions with 16 near sided occupants were identified. The intrusions listed are those closest to the occupant in question. Table 2 displays the injury data for each target vehicle occupant, as well as the on-scene estimation of injury in the impacting vehicle as reported by the police. Two case reports followed by a summary of the findings for the cases reviewed are presented.

Discussion

For each grouping of vehicle mismatch, definite patterns of injury and related sources are evident. Our results are similar to death risk results reported by the IIHS, who reported PV occupants were 3–4 times more likely to die than LTV occupants in frontal crashes between PV and LTV (5 deaths versus 0 in our series) (IIHS, 1999). For side impacts, they reported a 27–48-fold greater risk of death for PV occupants (5 versus 0 in our series). Of note, there were no LTV occupants who struck the

Acknowledgements

This project was supported by the National Highway Traffic Safety Administration (NHTSA)/Crash Injury Research and Engineering Network (CIREN) and the Robert Wood Johnson Clinical Scholars Program. The views expressed in this article are those of the authors and do not necessarily represent the views of the Robert Wood Johnson Foundation.

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