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A decade ago, James, et.al. published a detailed study of the available NASS data on severe rear impacts, with findings that “… stiffened or rigid seat backs will not substantially mitigate severe and fatal injuries in rear impacts.” No field accident study has since been advanced which refutes this finding. Advocates of rigidized seat backs often point to specific cases of severe rear impacts in which MAIS 4+ injuries are associated with seat back deformation, coupled with arguments supporting stiffer seatback designs. These arguments are generally based upon laboratory experiments with dummies in normal seating positions. Recent field accident data shows that generally, in collisions where the majority of societal harm is created, yielding seats continue to provide benefits, including those associated with whiplash associated disorders (WAD).

The BSAN crash pulse model has been shown to provide useful information for restraint sensing evaluation and for structural force-displacement studies in flat fixed rigid barrier (FFRB) crashes. This paper demonstrates a procedure by which the model may be extended for use with central and offset vehicle to vehicle (VTV) crashes through appropriate combinations of vehicle parameters.

The original Malibu II study, conducted by Bahling et al, found that neck compression loading in rollover crashes is caused by the occupant moving toward the ground and therefore, roof crush was not causally related to the loading. Some have disputed this finding claiming that the occupant does not “dive toward the roof,” but rather, the roof “moves in” toward the occupant, and that roof deformation is the primary cause of cervical spine injuries in rollover crashes. The original study included a detailed analysis of film and force transducer data for 10 Potentially Injurious Impacts (PII's). This paper presents an independent analysis of these 10 PII's and one additional PII. This analysis uses the film and transducer data to evaluate the timing of roof deformation and neck loading, the magnitude of roof deformation at the time of peak neck load, and the motion of the vehicle and occupants in the inertial reference system.

Understanding of events within the history of a crash, and estimation of the severity of occupant interior collisions depend upon an accurate assessment of crash duration. Since this time duration is not measured independently in most crash test reports, it must usually be inferred from interpretations of acceleration data or from displacement data in high-speed film analysis. The significant physical effects related to the crash pulse are often essential in reconstruction analyses wherein the estimation of occupant interior “second collision” or airbag sensing issues are at issue. A simple relation is presented and examined which allows approximation of the approach phase and separation phase kinematics, including restitution and pulse width. Building upon previous work, this relation allows straightforward interpretation of test data from related publicly available test reports.

Field experience has consistently indicated that lap-only belts and lap-shoulder belts perform well and about equally in prevention of fatalities and serious injuries in the rear seating positions. Analyses based on overall usage and injury figures from the Fatal Analysis Reporting System (FARS), double-pair analysis of FARS data, and still older data bases have shown that, in the rear outboard seating positions, injury rates are about the same for lap-only and lap-shoulder belted crash occupants. Although sparse, recently available field data from the 1988-2001 National Analysis Sampling System / Crashworthiness Data System (NASS/CDS) files confirm the finding that, when used by rear seat occupants, lap-only belts perform about equally with lap-shoulder belts as countermeasures for serious and fatal injury in severe frontal crashes.

Occupant simulation models have been used to study trends or specific design changes in “typical” accident modes such as frontal, side, rear, and rollover. This paper explores the usage of the Articulated Total Body Program (ATB) as an accident reconstruction tool. The importance of model validation is discussed. Specific areas of concern such as the contact model, force-deflection data, occupant parameters, restraint system models, head/neck loadings, padding, and intrusion are discussed in the context of accident reconstruction.

This study is an extension of previous work on driver air bag deployment loads which used the mid-size male Hybrid Ill dummy. Both small female and mid-size male Hybrid Ill dummies were tested with a range of near-positions relative to the air bag module. These alignments ranged from the head centered on the module to the chest centered on the module and with various separations and lateral shifts from the module. For both sized dummies the severity of the loading from the air bag depended on alignment and separation of the dummy with respect to the air bag module. No single alignment provided high responses for all body regions, indicating that one test at a typical alignment cannot simultaneously determine the potential for injury risk for the head, neck, and torso. Based on comparisons with their respective injury assessment reference values, the risk of chest injury appeared similar for both sized dummies.

Measurement of chest compression is vital to properly assessing injury risk for restraint systems. It directly relates chest loading to the risk of serious or fatal compression injury for the vital organs protected by the rib cage. Other measures of loading such as spinal acceleration or total restraint load do not separate how much of the force is applied to the rib cage, shoulders, or lumbar and cervical spines. Hybrid III chest compression is biofidelic for blunt impact of the sternum, but is “stiff” for belt loading. In this study, an analysis was conducted of two published crash reconstruction studies involving belted occupants. This provides a basis for comparing occupant injury risks with Hybrid III chest compression in similar exposures. Results from both data sources were similar and indicate that belt loading resulting in 40 mm Hybrid III chest compression represents a 20-25% risk of an AIS≥3 thoracic injury.

Studies conducted in the 1970's suggested that inflatable belt restraints might provide a high level of occupant protection based on experiments with dummies, cadavers and volunteers. Although inflating the belt was one factor which contributed to achieving these experimental results, much of the reported performance was associated with other features in the restraint system. Exploratory experiments with the Hybrid III dummy indicated similar trends to previous studies, belt inflation reducing dummy response amplitudes by pretensioning and energy absorption while reducing displacement. The potential advantage of an increased loaded area by an inflatable belt could not be objectively demonstrated from previous studies or from dummy responses. Clearly, belt inflation can be one component of a belt restraint system which tends to reduce test response amplitudes. However, other belt system configurations have demonstrated similar test response amplitudes.

Recent detailed field accident data are examined with regard to injuries associated with rear impacts. The distribution of “Societal Harm” associated with various injury mechanisms is presented, and used to evaluate the performance of current seat back and restraint system designs. Deformation associated with seat back yield is shown to be beneficial in reducing overall Societal Harm in rear impacts. The Societal Harm associated with ejection and contact with the vehicle rear interior (the two injury mechanisms addressed by a rigid seat approach), is shown to be minimal. The field accident data also confirm that restraint usage in rear impacts has a substantial injury-reducing effect. Laboratory tests and computer simulations were run to investigate the mechanism by which seat belts protect occupants in rear impacts.

Impact tests were conducted on thirty-one unembalmed human cadaver heads. Impacts were delivered to the temporo-parietal region of fixed cadavers by two, different sized, flat-rigid impactors. Yield fracture force and stiffness data for this region of the head are presented. Impactor surfaces consisted of a 5 cm2 circular plate and a 52 cm2 rectangular plate. The average stiffness value observed using the circular impactor was 1800 N/mm, with an average bone-fracture-force level of 5000 N. Skull stiffness for the rectangular impactor was 4200 N/mm, and the average fracture-force level was 12,500 N.

Hyge sled tests were conducted using a rear-seat sled fixture to evaluate submarining responses (the lap belt of a lap-shoulder belt restraint loads the abdominal region instead of the pelvis). Objectives of these tests included: an evaluation of methods to determine the occurrence of submarining; an investigation into the influence of restraint system parameters, test severity, and type of anthropomorphic test device on submarining response; and an exploration of the mechanics of submarining. This investigation determined that: 1. Slippage of the lap belt off the pelvis due to dynamic loading of the dummy and the resulting kinematics can cause abdominal loading to the dummy in laboratory crash testing. 2. The 5th female dummy submarined more easily than did the Hybrid ill in the test environment. 3. Motion of the pelvis was controlled using a “pelvic stop”, which reduced the submarining tendency for both the 5th female and Hybrid III dummies. 4.

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.

Results indicate the need for a redesigned Hybrid III face capable of accurate force and acceleration measurements. New instrumentation and methods for facial fracture detection were developed, including the application of acoustic emissions. Force/ deflection information for the human cadaver head and the Hybrid III ATD were generated for the frontal, zygomatic, and maxillary regions.

Nineteen sled impact tests were conducted simulating a frontal collision exposure for an unrestrained driver. The deceleration sled buck configuration utilized the passenger compartment of a late model compact passenger vehicle, a rigid driver's seat, and a custom fabricated energy-absorbing steering column and wheel assembly. Sled impact velocities ranged from 24.1 to 42.6 km/hr. The purpose of the study was to investigate the kinematic and kinetic interaction of the driver and the energy-absorbing steering assembly and their relationship to the thoracic/abdominal injuries produced. The similarities and differences between human cadaver and anthropomorphic dummy subjects were quantified.

Injury and disability associated with head (brain), neck (spinal cord) and facial injury account for 61.7% of the total societal Harm in the most recent estimate of motor-vehicle related crash injuries. This paper discusses the need for accurate information on translational and rotational acceleration of the head as the first step in critiquing the Head Injury Criterion (HIC) and other injury predictive methods, and developing a fuller understanding of brain and spinal cord injury mechanisms. A measurement system has been developed using linear accelerometers to accurately determine the 3D translational and rotational acceleration of the Hybrid III dummy head. Our concept has been to use the conventional triaxial accelerometer in the dummy's head to assess translational acceleration, and three rows of in-line linear accelerometers and a least squares analysis to compute statistical best-fits for the rotational acceleration about three orthogonal axes.

An economical alternative technique is presented for obtaining vehicle frontal crush characteristics from a series of repeated low speed barrier crashes. Results were analyzed using a technique of linear correlation of residual crush depth with a defined crush energy parameter. The data compared closely with crashes reported in the literature, and suggested that the structure exhibits only a slight strain rate sensitivity. Crush energy is shown to correlate well with dynamic crush depth. Relations among dynamic and residual crush and recovery distance are reported, Velocity restitution is shown to be about constant at 15% over the impact velocity range employed. A force-deflection relation based on the offset force linear harmonic oscillator theory is suggested, shown to agree quite well with data. Repeated crash testing can be an effective method to obtain information needed for development of analytical and predictive tools useful in design and reconstruction.

This paper summarizes the development of an Instrumented faceform which can record time histories of impact-related pressures at fifty-two locations over the entire face of a Hybrid 2 crash dummy skull. Pressures are measured by using piezo-electric, thin-plastic films; a high-speed, multiplex data acquisition system; signal conditioning; a software-controlled computerized data reduction and recording scheme; and a submergence calibration technique. The construction of the modified dummy face and the calibration gear are discussed. Examples of preliminary laboratory impact test results are presented. Theory and techniques relating to signal processing software, microprocessor controlled random-access-memory data-retrieval system and system calibration are also discussed. It is hoped that this tool, now undergoing final development and verification testing, will find extensive use in the evaluation and safety-related design of vehicle interiors and occupant restraints.

The relatively rare occurrence of injury or fatality in fuel-fed fires has received considerable attention in automotive safety rulemaking and products liability litigation. The literature related to fatalities associated with fire is confirmed by recent FARS data, and there are no reliable field data which confirm a need for further injury-reducing effect related to FMVSS 301. NHTSA has acknowledged this by removing crash fire rulemaking from its priorities plan. The police-reported crash fire data now available must be supplemented with in-depth investigation by trained teams before informed judgements can be made regarding further safety improvements with respect to crash fire injury.

The CRASH3 computer program, a well known and useful tool in accident reconstruction, is shown to be innaccurate by comparison with car-to-car crash test data. Claims for accuracy of about 10 percent cannot be validated. Both the impact model and the damage only model yield results which are in error. Cases involving error well in excess of 20 percent are demonstrated. These inaccuracies are due primarily to the omission of terms in the formulation of the energy equation and to the sensitivity of the solution to the input estimate of principle-direction-of-force.