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The NHTSA notices of proposed rulemaking on side impact protection have focused worldwide attention on one of the most difficult and frustrating efforts in automobile crash safety. Traditional vehicle design has evolved obvious structural contrasts between the side of the struck vehicle and the front of the striking vehicle. Protection of near-side occupants from intruding door structure is a most perplexing engineering challenge. Much useful and insightful engineering work has been done in conjunction with NHTSA's proposed rulemaking. However, there are many major engineering issues which demand further definition before reasonable side impact rulemaking test criteria can be finalized. This paper reviews recent findings which characterize the human factors, biomechanics, and occupant position envelope of the typical side impact crash victim.

Thanks to years of research and development by vehicle manufacturers, suppliers, legislation, and the entire safety community, the side airbag has become a critical safety device to reduce injury and save lives. This new collection of technical research highlights the progression of these essential safety features, providing a complete and thorough perspective through the analysis of both early patents and recent side airbag system developments. Advances in Side Airbag Systems begins with an introduction by editor Donald E. Struble, chronicling the progress made since the mid-1980s in offering improved side impact protection to the motoring public. Authored by leading experts in their respective fields, this book features a comprehensive collection of 26 landmark technical papers. Its scope includes not only thorax airbags, but other inflatable devices designed for side impacts and rollovers.

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.

An understanding of fundamental kinematic relationships among the several deforming surfaces of side-impacting bullet and target vehicle, occupant protection system and occupant is fundamental to rational design of crash injury counter-measures. Unfortunately, such understanding is not easy to achieve. Side impacts address the full range of bodily contacts and injuries in a way that challenges analysis. Each bodily area and organ requires individual consideration for adequate injury protection. This paper presents a simplified graphical analysis of occupant kinematics and injury exposure applied specifically to the NHTSA-proposed crabbed moving deformable barrier (MDB) compartment impact, as described in NHTSA's Notice of Proposed Rulemaking (NPRM) for Federal Motor Vehicle Safety Standard (FMVSS) 214, issued in January of 1988 [NHTSA 1988 (1)*]. Projections are offered regarding the potential of thoracic injury counter-measures.

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.

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.

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.

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.

A key aspect of accident reconstruction is the calculation of how much kinetic energy is dissipated as crush. By far the most widely used methods are derivatives of Campbell’s work, in which a linear relationship between residual crush and closing speed is shown to imply an underlying linearity between force and crush. “Consant-stiffness model” is the term used for such a representation of structural behavior. Difficulties arise, however, when significant non-uniformities are present in the crush pattern (as in narrow-object and/or side impacts, for example). The term “residual crush” becomes more ambiguous. Do we mean maximum crush, area-weighted average crush, or some other measure of residual deformation? And is it sufficient to represent the non-uniform crush pattern by a single parameter? Such considerations led to a re-development of the fundamental structural models, with an eye to determining whether the classical constant-stiffness model is the most appropriate.

Vehicle accident reconstruction methods based on deformation energy are argued to be an increasingly valuable tool to the accident reconstructionist, provided reliable data, reasonable analysis techniques, and sound engineering judgement accompany their use. The evolution of the CRASH model of vehicle structural response and its corresponding stiffness coefficients are reviewed. It is concluded that the deformation energy for an accident vehicle can be estimated using the CRASH model provided that test data specific to the accident vehicle is utilized. Published stiffness coefficients for vehicle size categories are generally not appropriate. For the purpose of estimating vehicle deformation energy, a straight-forward methodology is presented which consists of applying the results of staged crash tests. The process of translating crush profiles to estimates of vehicle deformation energies and velocities is also discussed.

This project covers one facet of a program to develop a mechanical model for characterizing the time history of local forces on the zygomatic, maxillary and mandible regions of the human face during a frontal collision. Two mechanical devices to measure the forces on crash dummies during testing were designed, constructed and tested. The devices employed cantilever beams equipped with strain gauges. Both devices were subjected to a series of drop tests onto various materials. Time histories were compared to those obtained from cadaver experiments. While the data obtained from this testing appears to be similar to the cadaver data, further improvements and modifications will make the model much more useful.

The reconstruction of accidental impacts to the side structure of one or more accident vehicles often incorporates estimates of the energy absorbed by laterally struck vehicle(s). Such estimates generally involve considerably more issues than does the assessment of frontal or rear impact deformation energy. The sides of vehicles are, compared to the usual striking object, relatively broad, and they contain zones of varying stiffness supported by collapsible box structures. Side stiffnesses can vary widely, depending upon impact geometry. Most side impact crash tests that can readily be used to make estimates of side stiffness have been conducted by the National Highway Traffic Safety Administration (NHTSA).

The issues of front seat energy absorption and seat belt effectiveness are investigated first through the review of prior experimental and analytical studies of rear impact dynamics. These prior studies indicate that the current energy absorption characteristic of seats is a safety benefit. Prior efforts to construct a rigidized seat indicate that such designs are likely to be impractical due to excessive weight and cost. Additionally, these studies indicate that seat belts provide an important safety function in rear impacts. Static tests of production seats were conducted, added to an existing data base, and analyzed to better understand the strength and energy absorbing characteristics of production seats. Crash test results from the New Car Assessment Program as well as earlier test programs were analyzed to describe the response of occupants and seats in rear impact and the protective function of seat belts in such collisions.

The determination of appropriate friction coefficient values is an important aspect of accident reconstruction. Tire-roadway friction values are highly dependent on a variety of physical factors. Factors such as tire design, side force limitations, road surface wetness, vehicle speed, and load shifting require understanding if useful reconstruction calculations are to be made. Tabulated experimental friction coefficient data are available, and may be improved upon in many situations by simple testing procedures. This paper presents a technical review of basic concepts and principles of friction as they apply to accident reconstruction and automobile safety. A brief review of test measurement methods is also presented, together with simple methods of friction measurement to obtain more precise values in many situations. This paper also recommends coefficient values for reconstruction applications other than tire- roadway forces.

The relationship between occupant crash injury and occupant compartment intrusion is seen in the perspectives of the velocity-time analysis and the NCSS statistical data for two important accident injury modes, lateral and rollover collisions. Restraint system use, interior impacts, and vehicle design features are considered. Side impact intrusion is analyzed from physical principles and further demonstrated by reference to staged collisions and NCSS data. Recent publications regarding findings of the NCSS data for rollovers, as well as the NCSS data itself, are reviewed as a background for kinematic findings regarding occupant injury in rollovers with roof crush.

Heavier, larger pickups and SUVs are bound to encounter lighter, smaller passenger vehicles in many future accidents. As the fleet has evolved to include more and more SUVs, their frontal structures are often indistinguishable from pickup fronts. Improvements in geometric compatibility features are crucial to further injury prevention progress in side impact. In corner crashes where modern bullet passenger car (PC) bumpers make appropriate geometrical overlap with target PC rocker panels, concentrated loads sometimes disrupt foam and plastic bumper corners, creating aggressive edges. In situations where sliding occurs along the structural interface, these sharp edges may slice through doors, panels and pillars. End treatments for such bumper beams should be designed to reduce this aggressive potential.

The National Highway Traffic Safety Administration (NHTSA) has recently opened a rulemaking docket seeking comments on the design of automobile seats and their performance in rear Impacts. There are two philosophies of seat design: one advocates rigid seats, the other advocates seats which yield in a controlled manner. A review of the legislative history of seat back design standards indicates that yielding seats have historically been considered a better approach for passenger cars. The design characteristics of current production automobile seats are evaluated and show no significant changes over the past three decades. Concerns about the performance of rigid seat backs in real world rear impacts are discussed, specifically increased injury exposure due to ramping, rebound and out-of-position occupants.

Rear impacts in the crash test data base compiled by the NHTSA are analyzed and compared to the CRASH3 rear stiffness coefficients. The CRASH3 values do not represent the test data adequately. This is because the values were derived from limited data, and because some of the rear moving barrier test data were miscoded as fixed barrier tests. A review of the larger NHTSA data base does not support the CRASH3 assumption that vehicles of similar size (wheelbase) have similar rear stiffness characteristics. Therefore, it is important when reconstructing individual accidents to use crash test data specific to the vehicles involved. Repeated rear fixed barrier test data on four vehicles are analyzed to study the data trend at speeds below and above the NHTSA test data. Constant stiffness and constant force models are compared and a combination of the two is shown to fit available test data.

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.