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The purpose of this study was to investigate approaches evaluating the performance of safety systems in crash tests and by analytical simulations. The study was motivated by the need to consider the adequacy of injury criteria and tolerance levels in FMVSS 208 measuring safety performance of restraint systems and supplements. The study also focused on additional biomechanical criteria and performance measures which may augment FMVSS 208 criteria and alternative ways to evaluate dummy responses rather than by comparison to a tolerance level. Additional analysis was conducted of dummy responses from barrier crash and sled tests to gain further information on the performance of restraint systems. The analysis resulted in a new computer program which determined several motion and velocity criteria from measurements made in crash tests.

This paper contains a review of current information on biological structure, material properties and failure characteristics of bone, articular cartilage, ligament and tendon. The load-deformation response of biological tissues is presented with particular reference to the microstructure of the material. Although many of the tissues have been characterized as linear, elastic and isotropic materials, they actually have a more complicated response to load, which includes stiffening with increasing strain, inelastic yield, and strain rate sensitivity. Failure of compact and cancellous bone depends on the rate, type, and direction of loading. Soft biological tissues are vlscoelastie and exhibit a higher load tolerance with an increasing rate of loading. The paper includes a discussion on the basic principles of biomechanics and emphasizes material properties and failure characteristics of biological tissues subjected to impact loading.

Life threatening chest injury can involve partial or full tears of the aorta. Investigations of fatal injuries in automobile accidents indicate that aortic trauma occurs in 10-20% of the cases. The major sites of aortic trauma include the aortic isthmus, the root, and the aortic insertion at the diaphragm - all of which are points of aortic tethering. The biomechanics of the injury process involve stretching of the vessel from points of tethering and hydrodynamic increases in blood pressure, which stretch the tissue to failure at a strain of about 150%. The non-isotropic stretch response of aortic tissue is discussed with reference to the frequent transverse orientation of the laceration. Congenital and pathophysiological conditions also influence the failure characteristics of the tissue. The significant factors associated with traumatic injury of the aorta are discussed in this review paper which is based on published technical information.

Knee bolsters on the lower instrument panel have been designed to control occupant kinematics during sudden deceleration. However, a wide variability in car occupant anthropometry and choice of seating posture indicates that lower-extremity contacts with the impingement bolster could predominantly load the flexed leg through the knee (acting through the femur) or through the tibia (acting through the knee joint). Potential injuries associated with these types of primary loading may vary significantly and an understanding of potential trauma mechanisms is important for proper occupant restraint.

Thoracic impact response and injuries of living and postmortem porcine siblings were investigated to quantify comparative differences. Thirteen male animals, averaging 61.4 kg, from five different porcine litters comprised the two animal samples. Porcine brothers were subjected to similar impact exposures for which at least one brother was tested live, anesthetized and another dead, post rigor with vascular repressurization. Statistically significant differences in biomechanical responses and injuries were observed between live and postmortem siblings. On the average the anesthetized live animals demonstrated a greater thoracic compliance, as measured by increased normalized total deflections (21% Hi), and reduced overall injuries (AIS 14% Lo and rib fractures 26% Lo) at lower peak force levels (13% Lo) than did the postmortem subjects. However, individual comparisons of “match-tested” siblings demonstrated very similar responses in some cases.

A femur fracture injury criterion is presented that assesses the dependence of the permissible human knee load on the duration of the primary force exposure. Currently a constant allowable femur load limit of 7.6 kN (1700 lb) is specified in FMVSS 208, but recently the Federal Government proposed elevating the allowable limit to 10.0 kN (2250 lb), which is in excess of the limited experimental average static femur fracture force of 8.90 kN (2000 lb). A general analysis of all of the available biomechanics data and mathematical models on femoral impact response and fracture indicates a significant load time dependence for primary pulse durations below 20 ms that can elevate the permissible femur load above the Federally proposed allowable limit of 10.0 kN (2250 lb).

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.

Airbags and safety belts are now viewed as complements for occupant protection in a crash. There is also a view that no single solution exists to ensure safety and that a system of protective technologies is needed to maximize safety in the wide variety of real automotive crashes. This paper compares the fatality prevention effectiveness, and biomechanical principles of occupant restraint systems. It focuses on the effectiveness of various systems in preventing fatal injury assuming the restraint is available and used. While lap-shoulder belts provide the greatest safety, airbags protect both belted and unbelted occupants.

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.

This paper covers the development of the General Motors Energy Absorbing Steering System beginning with the work of the early crash injury pioneers Hugh DeHaven and Colonel John P. Stapp through developments and introduction of the General Motors energy absorbing steering system in 1966. evaluations of crash performance of the system, and further improvement in protective function of the steering assembly. The contributions of GM Research Laboratories are highlighted, including its safety research program. Safety Car, Invertube, the biomechanic projects at Wayne State University, and the thoracic and abdominal tolerance studies that lead to the development of the Viscous Injury Criterion and self-aligning steering wheel.

Objective: This study analyzes rear sled tests with a 95th% male and 5th% female Hybrid III dummy in various seating positions on ABTS (All Belt to Seat) seats in severe rear impact tests. Dummy interactions with the deforming seatback and upper body extension around the seat frame are considered. Methods: The 1st series involved an open sled fixture with a Sebring ABTS seat at 30 mph rear delta V. A 95th% Hybrid III dummy was placed in four different seating positions: 1) normal, 2) leaning inboard, 3) leaning forward and inboard, and 4) leaning forward and outboard. The 2nd series used a 5th% female Hybrid III dummy in a Grand Voyager body buck at 25 mph rear delta V. The dummy was leaned forward and inboard on a LeSabre ABTS or Voyager seat. The 3rd series used a 5th% female Hybrid III dummy in an Explorer body buck at 26 mph rear delta V. The dummy was leaned forward and inboard on a Sebring ABTS or Explorer seat.

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.

Biomechanical surrogates are used in various forms to study head impact response in automotive applications and for assessing helmet performance. Surrogate headforms include those from the National Operating Committee on Standards for Athletic Equipment (NOCSAE) and the many variants of the Hybrid III. However, the response of these surrogates to loading at the chin and how that response may affect the loads transferred from the jaw to the rest of the head are unknown. To address part of that question, the current study compares the chin impact response performance of select human surrogates to that of the cadaver. A selection of Hybrid III and NOCSAE based surrogates with fixed and articulating jaws were tested under drop mass impact conditions that were used to describe post mortem human subject (PMHS) response to impacts at the chin (Craig et al., 2008). Results were compared to the PMHS response with cumulative variance technique (Rhule et al., 2002).

Active head restraints are being used to reduce the risk of whiplash in rear crashes. However, their evaluation in laboratory tests can vary depending on the injury criteria and test dummy. The objective of this study was to conduct barrier tests with BioRID and sled tests with Hybrid III to determine the most meaningful responses related to whiplash risks in real-world crashes. This study involved: (1) twenty-four rear barrier tests of the Saab 9000, 900, 9-3 and 9-5 with two fully instrumented BioRID dummies placed in the front or rear seats and exposed to 24 and 48.3 km/h barrier impacts, and (2) twenty rear sled tests at 5-38 km/h delta V in three series with conventional, modified and SAHR seats using the Hybrid III dummy. A new target superposition method was used to track head displacement and rotation with respect to T1. Insurance data on whiplash claims was compared to the dummy responses.

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.

During the past decade, there has been a steady increase in studies addressing rollover crashes and injuries. Though rollovers are not the most frequent crash type, they are significant with respect to serious injury and interest in rollovers has grown with the introduction of SUVs, vans, and light trucks. A review of Occupant and Vehicle Responses in Rollovers examines relevant conditions for field roll overs, vehicle responses, and occupant kinetics in the vehicle. This book edited by Dr. David C. Viano and Dr. Chantal S. Parenteau includes 62 technical documents covering 15 years of rollover crash safety, including field crash statistics, pre- and rollover dynamics, test procedures and dummy responses.

The problem of occupant impact severity reduction by effective use of available space was studied using a two-degree-of-freedom linear mathematical model implemented on a digital computer. An optimum-search method was employed to find the best values of stiffness and damping terms for linear lap and shoulder “belts” corresponding to specific vehicle pulseforms and geometry at speeds 10 to 60 mph. System performance was evaluated on the basis of a severity index comparing occupant deceleration data, and upon penalties imposed for occupant contact with vehicle interior structures. Comparison to biomechanical data indicates that the optimal linear system for 60 mph could produce serious injuries. Comparison to theoretical optimum values indicates considerable room for improvement, using active or nonlinear passive systems.

Objective: This study analyzed available rear impact sled tests with Starcraft-type seats that use a diagonal belt behind the seatback. The study focused on neck responses for out-of-position (OOP) and in-position seated dummies. Methods: Thirteen rear sled tests were identified with out-of-position and in-position 5 th , 50 th and 95 th Hybrid III dummies in up to 47.6 mph rear delta Vs involving Starcraft-type seats. The tests were conducted at Ford, Exponent and CSE. Seven KARCO rear sled tests were found with in-position 5 th and 50 th Hybrid III dummies in 21.1-29.5 mph rear delta Vs involving Starcraft-type seats. In all of the in-position and one of the out-of-position series, comparable tests were run with production seats. Biomechanical responses of the dummies and test videos were analyzed.