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Blunt impacts to the back of the torso can occur in vehicle crashes due to interaction with unrestrained occupants, or cargo in frontal crashes, or intrusion in rear crashes, for example. Six pendulum tests were conducted on the back of an instrumented 50th percentile male Hybrid III ATD (Anthropomorphic Test Device) to determine kinematic and biomechanical responses. The impact locations were centered with the top of a 15-cm diameter impactor at the T1 or at T6 level of the thoracic spine. The impact speed varied from 16 to 24 km/h. Two 24 km/h tests were conducted at the T1 level and showed repeatability of setup and ATD responses. The 16 and 24 km/h tests at T1 and T6 were compared. Results indicated greater head rotation, neck extension moments and neck shear forces at T1 level impacts. For example, lower neck extension was 2.6 times and 3.8 times greater at T1 versus T6 impacts at 16 and 24 km/h, respectively.

Objective: A friction rollover test was conducted as part of a rollover sensing project. This study evaluates vehicle and occupant responses in the test. Methods: A flat dolly carried a Saab 9-3 sedan laterally, passenger-side leading to a release point at 42 km/h (26 mph) onto a high-friction surface. The vehicle was equipped with roll, pitch and yaw gyros near the center of gravity. Accelerometers were placed at the vehicle center tunnel, A-pillar near the roof, B-pillar near the sill, suspension sub-frame and wheels. Five off-board and two on-board cameras recorded kinematics. Hybrid III dummies were instrumented for head and chest acceleration and upper neck force and moment. Belt loads were measured. Results: The vehicle release caused the tires and then wheel rims to skid on the high-friction surface. The trip involved roll angular velocities >300 deg/s at 0.5 s and a far-side impact on the driver’s side roof at 0.94 s. The driver was inverted in the far-side, ground impact.

Purpose: A better understanding of rear occupant fatality risks is needed to guide the development of safety improvements for 2nd and 3rd row occupants. This study investigates fatal accidents of 1st, 2nd and 3rd row occupants by principal direction of force (PDOF), irrespective of restraint use. It determined the number of fatalities, exposure and fatality risk. Methods: 1996-2005 FARS was analyzed for occupant fatalities by seating position (1st, 2nd and 3rd row) and principal direction of force (1-12 o'clock PDOF, rollover and other/unknown). Light vehicles were included with model year 1990+. 1996-2005 NASS-CDS was similarly analyzed for occupant exposure. Fatality risk was defined as the number of fatalities in FARS for a given category divided by the exposure from NASS-CDS. Results: Ten percent (9.6%) of fatalities were to 2nd row occupants in FARS. About 2,080 deaths occur to 2nd row occupants annually. 38.4% died in rollovers and 26.8% in frontal crashes.

Child safety is an important issue. The objective of this study was to analyze field accident data for 0-7 year old children in the 2nd row by vehicle and crash type, irrespective of restraint use. The data was obtained from NASS-CDS for calendar years 1991-2005. Accidents were selected based on 2nd row occupancy in towaway light vehicles with model year 1990 or newer. Side impacts caused 30.9% of serious-to-fatal injury (MAIS 3+F) to 2nd row children followed by frontal impacts (29.8%), rollovers (24.4%) and rear crashes (15.0%). The highest risk for MAIS 3+F was in rollovers (2.8 ± 0.7%) followed by rear (1.4 ± 0.4%), side (1.0 ± 0.2%) and frontal (0.46 ± 0.10%) crashes. The differences are statistically significant (p <0.01). Individual rear and frontal impact cases were also reviewed to better understand injury mechanisms of children in the 2nd row. The cases were obtained from the 1997-2005 NASS-CDS electronic database.

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.

Based upon a review of the literature and new test data, the human and vehicle factors leading to head-to-roof contact in rollovers are quantified and illustrated. Vehicle design countermeasures and suggested areas of research are presented. Higher and stronger roofs and improved restraints must be analyzed as a system to evaluate the potential benefits in rollovers.

This paper provides an overview of rollover crash safety, including field crash statistics, pre- and rollover dynamics, test procedures and dummy responses as well as a bibliography of pertinent literature. Based on the 2001 Traffic Safety Facts published by NHTSA, rollovers account for 10.5% of the first harmful events in fatal crashes; but, 19.5% of vehicles in fatal crashes had a rollover in the impact sequence. Based on an analysis of the 1993-2001 NASS for non-ejected occupants, 10.5% of occupants are exposed to rollovers, but these occupants experience a high proportion of AIS 3-6 injury (16.1% for belted and 23.9% for unbelted occupants). The head and thorax are the most seriously injured body regions in rollovers. This paper also describes a research program aimed at defining rollover sensing requirements to activate belt pretensioners, roof-rail airbags and convertible pop-up rollbars.

In this study, U.S. crash data was analyzed to better understand bounce-over rollovers. Crash data was reviewed to evaluate the distribution of bounce-over crashes and injuries, initiation objects and impact locations. In passenger cars, bounce-over crashes account for 8.4% of rollovers but involve 36.2% of the seriously injured belted drivers. Most bounce-overs are initiated by contact with narrow objects such as a pole, tree or barrier, or large objects such as a ditch or embankment. Contact often occurs in the front of the vehicle. After contact, the vehicle yaws and rolls, and serious injuries are often sustained to the head. Based on field data, a laboratory test was developed to simulate a narrow object bounce-over. The test consists of towing a vehicle laterally on a fixture towards a stationary, angled barrier resting in gravel. The moving fixture is decelerated and the vehicle is released. The vehicle front impacts the edge of the barrier, simulating a narrow object impact.

This study compares the effect of US and European airbag deployments on injury outcomes for belted drivers in frontal crashes. Driver weight, height and seat track position was also examined in relation to those outcomes. This information may help to prioritize and guide the logic for “Smart” airbags. For the study, only airbag-equipped cars were considered. Two accident databases were used: 1) the weighted and unweighted National Accident Sampling System (NASS-CDS) from the US, calendar years 1995 to 1996, and 2) the unweighted Co-operative Crash Injury Study (CCIS) from the UK, calendar years 1992 to 1998. The parameters investigated were Injury Severity Score (ISS), Equivalent Test Speed (ETS), occupant weight, occupant height and seat location. For US drivers, the injury rate and occurrence were calculated using weighted data, while for UK drivers, the rate and occurrence were obtained using unweighted data.

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.

Rollover accidents are responsible for a significant percentage of crash injuries. Increasing seat belt restraint use is the most effective way to reduce rollover injuries. Injuries to restrained occupants are also of interest. It has been suggested that head/neck injuries are caused by roof crush, and that modification to roof structures and seat belt systems would lead to a substantial reduction in severe rollover injuries. Field accident data and rollover testing are used to evaluate the relationship between roof crush, seat belt design, and severe rollover injuries.

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.

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.

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.

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.

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.

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.

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.

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.