William T. Hollowell

THE AGGRESSIVITY OF LIGHT TRUCKS AND VANS IN TRAFFIC CRASHES

Light trucks and vans (LTVs) currently account for over one-third of registered United States passenger vehicles. Yet, collisions between cars and LTVs account for over one half of all fatalities in light vehicle-to-vehicle crashes. Nearly 60% of all fatalities in light vehicle side impacts occur when the striking vehicle is a LTV. This paper examines this apparent incompatibility between cars and LTVs in traffic crashes. An analysis of U.S. crash statistics is presented: (1) to explore the aggressivity of LTVs in impacts with cars, and (2) to identify those design imbalances between cars and LTVs, for example mass, stiffness, and geometry, which lead to these severe crash incompatibilities. (A) For the covering abstract of the conference see IRRD 492347.

Experiences in reverse-engineering of a finite element automobile crash model

The experiences encountered during the development, modification, and refinement of a finite element model of a four-door sedan are described. A single model is developed that can be successfully used in computational simulations of full frontal, offset frontal, side, and oblique car-to-car impacts. The simulation results are validated with test data of actual vehicles. The validation and computational simulations using the model show it to be computationally stable, reliable, repeatable, and useful as a crash partner for other vehicles.

The crash compatibility of cars and light trucks

This paper investigates the compatibility of cars, light trucks, and vans (LTVs) involved in traffic crashes. An analysis of U.S. crash statistics shows that, although LTVs currently account for approximately one–third of registered U.S. passenger vehicles, collisions between cars and LTVs account for over one–half of all fatalities in light vehicle–to–vehicle crashes. In these crashes, 81 percent of the fatally injured are found to be occupants of the car. These statistics suggest that LTVs and passenger cars are incompatible in traffic crashes, and that LTVs are the more aggressive of the two vehicle classes. The fundamental incompatibility between cars and LTVs is observed even when the analysis is restricted to collisions between vehicles of model year 1990 or later - indicating that, despite the availability of newer safety countermeasures, e.g., airbags, the incompatibility between cars and LTVs will persist in future fleets. Through examination of crash test results, field crash statistics, and vehicle measurements, the paper explores the design imbalances between cars and LTVs, e.g., mass, stiffness, and geometry, which lead to these severe crash incompatibilities.

SIMULATION OPTIMIZATION OF THE CRASHWORTHINESS OF A PASSENGER VEHICLE IN FRONTAL COLLISIONS USING RESPONSE SURFACE METHODOLOGY

Although computer simulation is regarded primarily as a tool for systems analysis, simulation can also be used in the process of systems optimization. This paper describes recent enhancements to a computer program package which enables the use of vehicle and occupant simulation models in determining the design of vehicles and restraints for maximum occupant impact protection. Also described is an application of this program package to determine the optimal design of a passenger vehicle involved in frontal collisions.

NHTSA’s Vehicle Compatibility Research Program

The National Highway Traffic Safety Administration (NHTSA) is conducting a research program to investigate the crash compatibility of passenger cars, light trucks and vans (LTV’s) in vehicle-to-vehicle collisions. NHTSA has conducted a series of eight full-scale vehicle-to-vehicle crash tests to evaluate vehicle compatibility issues. Tests were conducted using four bullet vehicles representing different vehicle classes striking a mid-size sedan in both side and oblique frontal crash configurations. The test results show a good correlation between vehicle aggressivity metrics and injury parameters measured in the struck car for the frontal offset tests, but not for the side impact tests.

NHTSA's Compatibility Research Program Update

This paper provides an update of NHTSA’s research activities in vehicle compatibility and aggressivity. This paper presents newly initiated efforts underway to develop test assessment methodologies intended to evaluate vehicle compatibility. The rigid barrier load cell data collected from 18 years of the agency’s New Car Assessment Program testing are reviewed to evaluate potential test measures that may be used to evaluate a vehicle’s compatibility in vehicle-to-vehicle crashes. These parameters are then evaluated using a series of vehicle-to-vehicle and moving deformable barrier (MDB)to-vehicle tests. In these tests, the face of the MDB has been instrumented with an array of load cells to compute test measures. This study is part of NHTSA’s ongoing compatibility research program and is being coordinated with the IHRA compatibility group.

Design Considerations for a Compatibility Test Procedure

A major focus of the National Highway Traffic Safety Administration’s (NHTSA) vehicle compatibility and aggressivity research program is the development of a laboratory test procedure to evaluate compatibility. This paper is written to explain the associated goals, issues, and design considerations and to review the preliminary results from this ongoing research program. One of NHTSA’s activities supporting the development of a test procedure involves investigating the use of an mobile deformable barrier (MDB) into vehicle test to evaluate both the self-protection (crashworthiness) and the partnerprotection (compatibility) of the subject vehicle. For this development, the MDB is intended to represent the median or expected crash partner. This representiveness includes such vehicle characteristics as weight, size, and frontal stiffness. This paper presents distributions of vehicle measurements based on 1996 fleet registration data. While there is still considerable work to be done to develop meaningful aggressivity metrics that relate to realworld crash performance, this paper summarizes NHTSA’s work to date in this area.

Finite Element Modeling of the Side Impact Dummy (SID)

A new numerical model of the side impact dummy (SID) was developed based on the DYNA3D finite element code. The model includes all of the material and structural details of SID that influence its performance in crash testing and can be run on an engineering work station in a reasonable time. This paper describes the development of the finite element model and compares model predictions of acceleration and displacements with measurements made in SID calibration experiments. Preliminary parameter studies with the model show the influence of material properties and design on the measurements made with the SID instrument.

Applications of NHTSA's Vehicle Parameter Database

This paper desribes the contents, development, and use of the NHTSAs Vehicle Parameter Database in accident data analysis and injury determination. The database also can be used as a source for vehicle information for computer model/simulation programs or in the development of crash avoidance measures. The analysis of damage sustained by vehicles in acidents is based on post-crash information and is somewhat limited since pre-crash measurements are not usually known or readily available. The ability to compare pre-crash and post-crash basic vehicle measurement characteristics provides greater insight into analyzing vehicle damage, degree of intrusion, level of deformation, and injury severity/source. The Vehicle Parameter Database consists of 101 key vehicle dimensions and specifications on more than 2800 vehicles from 1980 to 1994. (A) For the covering abstract of the conference see IRRD 882390.

NHTSA'S IMPROVED FRONTAL PROTECTION RESEARCH PROGRAM

In the United States, within the next few years air bags will be required in all passenger cars and light trucks under Federal Motor Vehicle Safety Standard (FMVSS) No. 208, Occupant Crash Protection. Even after full implementation of driver and passenger air bags as required by FMVSS No. 208, frontal impacts will still account for up to 8,000 fatalities and 120,000 moderate to critical injuries (i.e. injuries of AIS >= 2). The National Highway Traffic Safety Administration (NHTSA) has an ongoing research program to address these fatalities and injuries and provide a basis for the possible future upgrade of FMVSS No. 208. This effort includes developing supplementary test procedures for the evaluation of occupant injury in higher severity crashes, developing improved injury criteria including criteria for assessing injuries to additional body regions, and evaluating the injuries associated with occupant size. More recently, in monitoring the fleet performance of current air bag systems, NHTSA has identified aggressive air bag deployment as a potential cause of injuries and fatalities of occupants in minor severity crashes. Accordingly, the agency has added new activities to investigate this finding in its frontal crash protection research program. This paper presents an overview of the agencys overall research program. Selected results from the testing conducted to date are discussed. Finally, a discussion is presented toward improving occupant protection systems in frontal crashes. [A] For the covering abstract, see IRRD 896528.