Nhtsa's Recent Compatibility Test Program

NHTSA has developed and conducted a vehicleto-vehicle crash test program to evaluate the statistical correlation between vehicle performance measures and the probability of driver fatality in a crash partner vehicle. The test program uncovered some concerns regarding NHTSA’s rigid barrier data collection and review methods. The vehicle-tovehicle tests did not provide clear insight into the mechanism behind the fleet correlation, but did emphasize the complexity of vehicle compatibility and the changing safety priorities related to improved occupant restraints. INTRODUCTION In September 2002, the National Highway Traffic Safety Administration (NHTSA) formed an Integrated Project Team (IPT) to conduct an indepth review of vehicle compatibility [1]. This team was chartered to identify innovative solutions and recommend effective strategies to improve vehicle compatibility. One of the strategies developed by this team was to initiate a test matrix to investigate opportunities for vehicle crash partner protection. This paper documents the development, analysis, and results from this test program. In recent years, NHTSA has conducted several crash test and statistical studies to evaluate vehicle compatibility. These studies attempted to correlate the results from staged crash testing with the fatality and injury consequences observed from the accident databases. The IPT recommended a vehicle-tovehicle test program to explore the results published in the report, “Vehicle Weight, Fatality Risk, and Crash Compatibility [2].” In this report, Kahane evaluated the fatality risk to the driver of a passenger car when struck by another passenger car or an LTV. The fatality risk for vehicle models were compared against compatibility measures derived from U.S. New Car Assessment Program (NCAP) testing. The average height of force (AHOF) and initial stiffness were evaluated as predictors of real world crash outcomes [3]. Kahane found that the difference in the AHOF between the struck and the striking vehicles had a statistically significant negative effect on the fatality risk to a car driver struck on the left side. A passenger car driver struck by a vehicle with a relatively higher AHOF would have a greater risk of fatality. No correlation was found by Kahane for front-to-front crashes, but subsequent research indicated that a correlation exists only for belted drivers struck front-to-front by a vehicle with a higher relative AHOF [4]. In addition to the geometric aspects of AHOF, Kahane evaluated the energy absorption or front-end stiffness of the striking vehicle. NHTSA had previously developed a methodology to compute a front-end stiffness measure from a linear fit to the force-deflection profile in NCAP testing [3]. Kahane found that the stiffness of an LTV had a statistically significant positive effect on the fatality risk for a passenger car driver struck in the front. The study also found that the stiffness of a striking car in a left side impact had a statistically significant positive effect on the fatality risk of the struck car’s driver. In order to evaluate these statistical results, it was desired to implement a vehicle-to-vehicle test program to evaluate how the striking vehicle characteristics affect the safety performance [5]. It was decided to use three classes of bullet vehicles: minvans, SUVs, and pickups. Two vehicles from each category were selected to have similar size and weight, but with different compatibility measures. These six bullet vehicles were tested in a series of vehicle-to-vehicle crashes against a single target vehicle. The occupant injury measures in the target vehicle were used to assess the compatibility of the striking vehicle.