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Spine degeneration can lower injury tolerance and influence injury outcomes in vehicle crashes. To date, limited information exists on the effect of age and sex on thoracic spine 3-dimensional geometry. The purpose of this study is to quantify thoracic spinal column and canal geometry using selected geometrical measurement from a large sample of CT scans. More than 33,488 scans were obtained from the International Center for Automotive Medicine database at the University of Michigan under Institutional Review Board approval (HUM00041441). The sample consisted of CT scans obtained from 31,537 adult and 1,951 pediatric patients between the ages of 0 to 99 years old. Each scan was processed semi-automatically using custom algorithms written in MATLAB (The Math Works, Natick, MA). Five geometrical measurements were collected including: 1) maximum spinal curvature depth (D), 2) T1-to-T12 vertical height (H), 3) Kyphosis Index (KI), 4) kyphosis angle, and 5) spinal canal radius.

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.

This paper summarizes work relating to the assessment of societal benefits of side impact protection. National Crash Severity Study (NCSS) and National Accident Sampling System (NASS) accident data technigues were reviewed with respect to the reliability of output information concerning the distribution of side impact accidents by impact severity and relationships between injury and impact severity. NCSS and NASS are confounded by errors and inadequacies, primarily as a result of improper accident reconstruction based upon the CRASH computer program. Based on review of several sample cases, it is believed that the NCSS/NASS files underestimate Lower severities and overestimate higher severities in side impact, with delta-V errors probably overestimated by 25-30 percent in the case of the more serious accidents. These errors cannot be properly quantified except on a case-by-case basis. They introduce unknown biases into NCSS/NASS.

In 1995, new seat specifications were adopted by GM to provide high retention and improve occupant safety in rear crashes. With more than five years of phase-in of high retention (HR) seats, an analysis of FARS was undertaken to determine the initial field performance of HR seats in preventing fatalities. The 1991-2000 FARS was sorted for fatal rear-impacted vehicles. Using a VIN decoder, GM vehicles with HR front seats were sorted from those with baseline (pre-HR) seats. The fatal rear-impacted vehicle crashes were subdivided into several groups for analysis: 1) single-vehicle rear impacts, 2) two-vehicle rear crashes involving light striking vehicles, and 3) two-vehicle crashes involving heavy trucks and tractor-trailers, and multi-vehicle (3+) rear crashes.

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.

This paper reviews issues relating to seats including design for comfort and restraint, mechanics of discomfort and irritability, older occupants, and low-back pain. It focuses on the interface between seating technology and occupant comfort, and involves a technical review of medical-engineering information. The dramatic increase in the number of features currently available on seats outreaches the technical understanding of occupant accommodation and ride comfort. Thus, the current understanding of seat design parameters may not adequately encompass occupant needs. The review has found many pathways between seating features and riding comfort, each of which requires more specific information on the biomechanics of discomfort by pressure distribution, body support, ride vibration, material breathability, and other factors. These inputs stimulate mechanisms of discomfort that need to be quantified in terms of mechanical requirements for seat design and function.

An engineering analysis of vehicle braking is presented in terms of the utilization of available road friction. Physical relations are derived which allow the determination of optimum brake force distribution on front and rear wheels as a function of axle loading. Ideal braking distribution curves are shown for a typical vehicle in the loaded and unloaded conditions. A technique is suggested for rational design of braking system parameters. It is applied to the case of a two-stage proportioning system, and is validated by experimental data from tests using a specially equipped light truck. It is concluded that a proper design analysis can establish a combination of braking system parameters which results in improved utilization of available friction. A simple, self-adjusting brake proportioning system can be a highly cost-effective safety device for truck use.

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.

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.

Five anesthetized porcine subjects were exposed to blunt thoracic impact using a 21 kg mass with a flat contact surface traveling at 3.0 to 12.2 m/s. The experiments were conducted to assess the appropriateness of studying in vivo mechanical and physiological response to thoracic impact in a porcine animal model. A comprehensive review of comparative anatomy between the pig and man indicates that the cardiovascular, respiratory and thoracic skeletal systems of the pig are anatomically and functionally a good parallel of similar structures in man. Thoracic anthropometry measurements document that the chest of a 50 to 60 kg pig is similar to the 50th percentile adult male human, but is narrower and deeper. Peak applied force and chest deflection are in good agreement between the animal's responses and similar impact severity data on fresh cadavers.

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.

Vehicle fleet downsizing has been discussed in Europe as an aspect to reduce fuel emissions. A recently developed mathematical model was used to study the individual effects of fleet mass distribution, impact speed reductions and inherent vehicle protection on average injury and fatality rates for downsized fleets. A baseline fleet of 700-2000 kg was downsized by a) reducing all vehicle masses by 10% or 20% and b) by removing all cars heavier than 1400 or 1200 kg. The results showed that the safety can be maintained if the vehicle masses are reduced proportionally to their original mass. A higher safety level can be achieved by removing the heavier vehicles. Traffic safety can be further enhanced by impact speed reductions or by improvements of restraint systems and vehicle compatibility.

Objective: This study involved a number of different tests addressing theories for recliner and track release of front seats in rear impacts. It addresses the validity of the theories. Method: Several separate test series were conducted to address claims made about recliner and track release of front seats in rear impacts. The following theories were evaluated to see the validity of the issues: 1 Recliner teeth slipping with minimal damage to the teeth 2 Recliner teeth bypass by disengaging and re-engaging under load without damaging the teeth 3 Recliner shaft bending and torque releasing the recliners 4 Track release by heel loading 5 Track release with occupant load on the seat 6 Recliner handle rotation causing recliner release 7 Double pull body block tests Results: Many of the theories were found to be uncorroborated once actual test data was available to judge the merits of the issue raised. The laboratory tests were set-up to specifically address particular issues.

Seats have become stronger over the past two decades and remain more upright in rear impacts. While head restraints are higher and more forward providing support for the head and neck, serious-to-fatal injuries to the thoracic and cervical spine have been seen in occupants with spinal disorders, such as DISH (diffuse idiopathic skeletal hyperostosis), ankylosis, spondylosis and/or osteophytes that ossify the joints in the spine. This case study addresses the influence of spinal disorders on fracture-dislocation and spinal cord injury in rear impacts with relatively upright seats. Nineteen field accidents were investigated where serious-to-fatal injuries of the thoracic and cervical spine occurred with the seat remaining upright or slightly reclined. The occupants were lap-shoulder belted, some with belt pretensioning and cinching latch plate.

Objective: Sled test video and data were independently analyzed to assess the validity of statements and conclusions reported in Bidez et al. SAE paper 2005-01-1708 [7]. Method: An independent review and analysis of the test data and video was conducted for 9 sled tests at 35 km/h (21.5 mph). The 5th female Hybrid III was lap-shoulder belted in the 2nd or 3rd row seat of a SUV buck. For one series, the angle was varied from 0, 15, 30, 45 and 60 deg PDOF. The second series involved shoulder belt pretensioning and other belt modifications. Results: Bidez et al. [7] claimed “The lap belts moved up and over the pelvis of the small female dummy for all impact angles tested.” We found that there was no submarining in any of the tests with the production lap-shoulder belts. Bidez et al. [7] claimed “H3-5F dummies began to roll out of their shoulder belt at… 30 degrees. Complete loss of torso support was seen at 45 degrees without significant kinetic energy dissipation.”

Crash safety researchers have an increased concern regarding the decreased thoracic deflection and the contributing injury causation factors among the elderly population. Sternum fractures are categorized as moderate severity injuries, but can have long term effects depending on the fragility and frailty of the occupant. Current research has provided detail on rib morphology, but very little information on sternum morphology, sternum fracture locations, and mechanisms of injury. The objective of this study is two-fold (1) quantify sternum morphology and (2) document sternum fracture locations using computed tomography (CT) scans and crash data. Thoracic CT scans from the University of Michigan Hospital database were used to measure thoracic depth, manubriosternal joint, sternum thickness and bone density. The sternum fracture locations and descriptions were extracted from 63 International Center for Automotive Medicine (ICAM) crash cases, of which 22 cases had corresponding CT scans.

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.

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 study assesses vehicle and occupant responses in six vehicle-to-vehicle high-speed rear impact crash tests conducted at the Exponent Test and Engineering Center. The struck vehicle delta Vs ranged from 32 to 76 km/h and the vehicle centerline offsets varied from 5.7 to 114 cm. Five of the six tests were conducted with Hybrid III ATDs (Anthropometric Test Device) with two tests using the 50th male belted in the driver seat, one test with an unbelted 50th male in the driver seat, one test with a 95th male belted in the driver seat, and one with the 5th female lap belted in the left rear seat. All tests included vehicle instrumentation and three tests included ATD instrumentation. The ATD responses were analyzed and compared to corresponding IARVs (injury assessment reference values). Ground-based and onboard vehicle videos were synchronized with the vehicle kinematic data and biomechanical responses.

Seat strength has increased over the past four decades which includes a transition to dual recliners. There are seat collision performance issues with stiff ABTS and very strong seats in rear impacts with different occupant sizes, seating positions and physical conditions. In this study, eight rear sled tests were conducted in four series: 1) ABTS in a 56 km/h (35 mph) test with a 50th Hybrid III ATD at MGA, 2) dual-recliner ABTS and F-150 in a 56 km/h (35 mph) test with a 5th female Hybrid III ATD at Ford, 3) dual-recliner ABTS in a 48 km/h (30 mph) test with a 95th Hybrid III ATD leaning inboard at CAPE and 4) dual-recliner ABTS and Escape in 40 km/h (25 mph) in-position and out-of-position tests with a 50th Hybrid III ATD at Ford. The sled tests showed that single-recliner ABTS seats twist in severe rear impacts with the pivot side deformed more rearward than the stanchion side.