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Since air bags emerged as an occupant protection concept in the early '70s, their development into a widely-available product has been lengthy, arduous, and the subject of an intense national debate. That debate is well documented and will not be repeated here. Rather, operating principles and design considerations are discussed, using systems and components from the developmental history of airbags as examples. Design alternatives, crash test requirements, and performance limits are discussed. Sources of restraint system forces, and their connection with occupant size and position, are identified. Various types of inflators, and some of the considerations involved in “smart” systems, are presented. Sensor designs, and issues that influence the architecture of the sensor system, are discussed.

It is well known that occupant protection in side impacts involves technical complexities, and the development of effective countermeasures has become more urgent due to recent US Government rulemaking. The additional difficulties of experimental measurement and observation have caused an increased emphasis to be placed on simulation models for side impacts. There are several complex three-dimensional occupant models which provide representations of occupant kinetics, but simulations of the occupant's interaction with the vehicle are not well developed. In contrast, the simpler lumped-mass models are good at simulating vehicle structural dynamics, including door intrusion, but may not model the occupant well (head movements, for example). The present simulation is a lumped-mass model that seeks a middle ground.

In frontal crashes, lateral deformations can occur as a result of various mechanisms. Unfortunately, the crush energy associated with such deformations cannot be assessed as long as the structural properties are unknown. That has been the situation to date, due to the lack of appropriate crash test data. The present research attempts to address this deficit. A passenger car was crash-tested in a mode designed to induce lateral deformations that are significant compared to longitudinal crush. This was done via a series of three repeated impacts on the same vehicle so as to obtain, in a cost-effective manner, structural characterization data at increasing crash severities. Various cause-and-effect relationships (structural characterization models) were considered with an eye to selecting the one that best predicts the crush energy. Insights obtained from analyzing the behavior of the front structure are presented.

Collision Safety Engineering, Inc. (CSE), has developed a test prototype system to protect occupants during lateral impacts. It is an inflatable system that offers the potential of improved protection from thoracic, abdominal and pelvic injury by moving an impact pad into the occupant early in the crash. Further, it shows promise for head and neck protection by deployment of a headbag that covers the major target areas of B-pillar, window space, and roofrail before head impact. Preliminary static and full-scale crash tests suggest the possibility of injury reduction in many real-world crashes, although much development work remains before the production viability of this concept can be established. A description of the system and its preliminary testing is preceded by an overview of side impact injury and comments on the recent NHTSA Rule Making notices dealing with side-impact injury.

CRASH3 plays an important role in the development of accident data files, and in addition it is often used for reconstructing specific accidents. Had it been intended from the outset for this latter purpose, its development may have progressed along slightly different lines. It is now appropriate to examine the use of CRASH3 in specific accidents, the use of available crash test data, and the nature of the likely CRASH3 user. Suitably accounted for, all these factors would have a significant influence on the design of accident reconstruction algorithms, including any contemplated revisions of CRASH3. Such considerations are the subject of this paper.

Crush energy assessment methods rely on the characterization of a vehicle’s structure, through a comparison with crash tests of a similar vehicle. For frontal impacts, the vast majority of these tests involve a flat rigid barrier. When the reconstructionist is presented with a frontal underride/override crash, however, the structural load pattern and the deformation mode suggest that the comparison with flat barrier tests may not be valid. This has been confirmed by prior studies. With few exceptions, for any given vehicle, there are no crash data in an underride/override mode that are useful for analysis purposes. The purpose of this research was to bridge the gap so that flat barrier data, specific to the vehicle in question, could be applied to underride/override cases. This entailed the development of a measurement protocol, a structural model for such crashes, and a procedure for analyzing the load cell data that exist for many barrier crash tests.

Crash tests of vehicles by striking deformable barriers are specified by Government programs such as FMVSS 214, FMVSS 301 and the Side Impact New Car Assessment Program (SINCAP). Such tests result in both crash partners absorbing crush energy and moving after separation. Compared with studying fixed rigid barrier crash tests, the analysis of the energy-absorbing behavior of the vehicle side (or rear) structure is much more involved. Described in this paper is a methodology by which analysts can use such crash tests to determine the side structure stiffness characteristics for the specific struck vehicle. Such vehicle-specific information allows the calculation of the crush energy for the particular side-struck vehicle during an actual collision – a key step in the reconstruction of that crash.

This research examines the effects of impactor characteristics on the calculated structural stiffness parameters A and B for the struck sides of late-model vehicles. This study was made possible by crash testing performed by the National Highway Traffic Safety Administration involving side impacts of the same vehicle line with both a rigid pole and with a moving deformable barrier. Twenty-nine crash test pairs were identified for 2018 model-year vehicles. Of 60 total tests, 49 were analyzed. Test data for 19 vehicles impacted in both modes resulted in A and B values considered to be valid. Classifying these 19 vehicles according to the categories defined by Siddall and Day, only Class 2 multipurpose vehicles were represented by enough vehicles (10) to search for trends within a given vehicle category. For these vehicles, more scatter in the results was observed in both A and B values for the MDB impacts compared to the pole impacts.

Crash tests of vehicles by striking deformable barriers are specified by Government programs such as FMVSS 214, FMVSS 301 and the Side Impact New Car Assessment Program (SINCAP). Such tests result in both crash partners absorbing crush energy and moving after separation. Compared with studying fixed rigid barrier crash tests, the analysis of the energy-absorbing behavior of the vehicle side (or rear) structure is much more involved. Described in this paper is a methodology by which analysts can use such crash tests to determine the side structure stiffness characteristics for the specific struck vehicle. Such vehicle-specific information allows the calculation of the crush energy for the particular side-struck vehicle during an actual collision – a key step in the reconstruction of that crash.

Due to the upgrade of FMVSS 214 and the emergence of side NCAP tests, there is a growing body of crash test data on vehicle side structures. Such data would be very useful to reconstructionists, except that the struck vehicle behavior is masked, in part, by the use of a deformable moving barrier in the test. The post-impact dynamics and the energy absorption by the barrier itself must be accounted for if the desired vehicle structural characterization is to be extracted. Attempts prior to this paper to achieve a side structure characterization have dealt with these issues by invoking various simplifying assumptions. Unfortunately, these have not been supported by a foundation in either physics or measurement. Questions have also been raised whether prior characterizations of the barrier face are appropriate, in view of the prior crash modes being so unlike the FMVSS 214 test. To address these issues, crash tests of the barrier itself, in an appropriate crash mode, have been conducted.