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Purpose: This study investigates NASS-CDS data on basilar skull fractures by crash type and injury source for various crash scenarios to understand the injury risks, injury mechanisms and contact sources. Methods: 1993-2008 NASS-CDS data was used to study basilar skull fractures in adult front occupants by crash type and injury source. Injury risks were determined using weighted data for occupants with known injury status in 1994+ model year vehicles. In-depth analysis was made of far-side occupants in side impacts and rear crashes using the NASS electronic cases. Results: Basilar skull fractures occur in 0.507 ± 0.059% of rollovers and 0.255 ± 0.025% of side impacts. The lowest risk is in rear impacts at 0.015 ± 0.007%. The most common contact source is the roof, side rails and header (39.0%) in rollovers, the B-pillar (25.8%) in side impacts and head restraint (55.3%) in rear crashes.

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.

Door armrests of different crush properties and placement were evaluated in a series of side impact sled tests. Three armrest designs were fabricated with an identical shape but different crush force. The crush properties covered a range in occupant protection systems based on knowledge of human tolerance in side impacts. With BioSID, the softest armrest produced the lowest compression and Viscous responses, and the probability of AIS 4+ injury was below 1%. The compression-based responses increased significantly in tests with armrests of a higher crush force. The profile of the stiffer armrests clearly protruded into the dummy, and the probability of serious injury was 86%-100% based on compression. With SID, the lowest TTI(d) was with the intermediate stiffness armrest. The SID dummy and TTI(d) criterion indicated a 4%-8% probability of AIS 4+ injury for all test conditions and armrest designs.

Since more occupants are using rear seats of vehicles, a better understanding of priorities for rear occupant protection is needed as future safety initiatives are considered. A two-part study was conducted on occupant injuries in rear seating positions. In Part I, adult and teenage occupants ≥13 years of age are investigated. In Part II, children aged 4-12 years old and toddlers and infants aged 0-3 are studied separately because of the use of infant and child seats and boosters involve different injury mechanisms and tolerances. The objectives of this study on adult and teenager, rear-seated occupants (≥13 years old) are to: 1) review accident data, 2) identify the distribution of rear occupants, and 3) analyze injury risks in various crash modes, including rollovers, frontal, side and rear impacts. Three databases were investigated: NASS-CDS, GES and FARS.

Child safety continues to be an important issue in automotive safety for many reasons, including reported cases of serious injury from airbag deployments. As a result of extensive public education campaigns, most children are now placed in rear seats of vehicles. Accordingly, a more precise understanding of rear-seat occupant protection is developing as the second and third rows have become the primary seating area for children in SUVs, vans and passenger cars. The objective of this study was to review field crash and injury data from rear seats, identify the distribution of children and infants in rear seats, and analyze injury risks in various crash modes. The database used was the 1991-1999 NASS-CDS. When looking at crash configurations for 1st and 2nd row children, rollover crashes involved the highest incidence of MAIS 3+ injury, followed by frontal and side impacts. Lap-shoulder belt usage was similar for 1st and 2nd row children.

Side impact pendulum tests were conducted on Eurosid I and Biosid to assess the biofidelity of the thorax, abdomen and pelvis, and determine injury tolerance levels. Each body region was impacted at 4.5, 6.7, and 9.4 m/s using test conditions which duplicate cadaver impacts with a 15 cm flat-circular 23.4 kg rigid mass. The cadaver database establishes human response and injury risk assessment in side impact. Both dummies showed better biofidelity when compared to the lowest-speed cadaver response corridor. At higher speeds, peak force was substantially higher. The average peak contact force was 1.56 times greater in Biosid and 2.19 times greater in Eurosid 1 than the average cadaver response. The Eurosid I abdomen had the most dissimilar response and lacks biofidelity. Overall, Biosid has better biofidelity than Eurosid I with an average 21% lower peak load and a closer match to the duration of cadaver impact responses for the three body regions.

As the driving population ages, there is a need to understand the accident patterns of older drivers. Previous research has shown that side impact collisions, usually at an intersection, are a serious problem for the older driver in terms of injury outcome. This study compares the frequency of side impact, intersection collisions of different driver age groups using state and national police-reported accident data as well as an in-depth analysis of cases from a fatal accident study. All data reveal that the frequency of intersection crashes increases with driver age. The state and national data show that older drivers have an increase frequency of intersection crashes involving vehicles crossing paths prior to the collision compared to their involvement in all crash types. When taking into account traffic control devices at an intersection, older drivers have the greatest involvement of multiple vehicle crashes at a signed intersection.

Fatal crash circumstances for 48 belted female drivers were studied in-depth and compared to those of 83 belted male drivers in a similar population of vehicles. Women had a higher incidence of crashes on slippery roads, during lane changes and passing maneuvers than men who had a higher rate of aggressive driving and speed related crashes (χ2 = 10.47, p < 0.001). Driver-side damage was significantly more frequent in female than male crashes (χ2 = 5.74, p < 0.025) and women had a higher fraction of side impacts (45.9% v 31.4%) and crashes during daylight (87.0% v 72.3%, χ2 = 3.65, p < 0.05) than men. Women also had a higher fraction of potentially avoidable crashes than men (57.5% v 39.0%) and a lower involvement related to aggressive driving (10.6% v 25.6%). These differences were statistically significant (χ2 = 5.41, p < 0.025).

The timing of liver laceration in swine during the course of a blunt impact was investigated. The swine were impacted on the upper abdomen by the lower segment of a steering wheel at 6, 9 and 12 m/s. The degree of compression in each impact was controlled independently from 10 to 50%. By varying when “the punch of an impact was pulled,” we reproduced progressive segments of a longer duration blunt impact. Autopsy of the subjects demonstrated that lacerations were initiated after 8 ms of loading at 9 m/s and 6 ms of loading at 12 m/s. The time of injury was concurrent with the time when the Viscous response exceeded a threshold of 1.2 m/s in our specimens. The Viscous injury criterion, defined as the peak Viscous response, was found to be the best predictor of liver laceration. We conclude that the Viscous response relates to the actual etiology of injury, in addition to being an excellent correlative measure.

The purpose of this study was to replace the axial deforming elements in the current EUROSID dummy with spring steel ribs and attached damping material to provide improved biofidelity in the lateral chest impact response. This report provides a description of the design, construction, and evaluation of the modified EUROSID chest for injury assessment in side impact crashes. Three spring steel ribs were designed to provide stiffness and deflections of 120 mm when attached to the block on the spine of the EUROSID dummy. Damping material was epoxied to the ribs and the system provided biofidelity in the lateral impact response for blunt impact loading at 4.3 m/s and 6.7 m/s. The new design provides significantly reduced inertia of the near side rib cage, elastic and viscous properties that are representative of the lateral human response and the ability to measure the deflection response of the rib cage for injury assessment with the Viscous response.

This paper refines the methodology presented in the companion paper linking reductions in biomechanical responses due to force-limiting material to projections of injury-mitigation in real-world side impact crashes. The revised approach was used to evaluate the potential injury reducing benefit for the chest and abdomen with either constant crush force or constant stiffness, crushable material in the side door and armrest. Using a simulation of the human impact response, a range in crush force or stiffness was determined which reduced the viscous response from that obtained with a rigid impact. NCSS field accident data for car-to-car side impacts provided information on the occupant exposure and injury as a function of the change in velocity (ΔV) of the struck vehicle. Since the velocity of the side door at contact with the occupant's chest is similar to the ΔV of the struck vehicle, the chest impact velocity in the simulation was assumed equal to the observed ΔV in the NCSS data.

The NHTSA's side impact dummy (SID) was evaluated against what is known of the side impact response of the human chest and responses were compared with data on Hybrid III frontal and EURQSID side impact characteristics. The SID dummy lacks a human-like chest deflection response which is crucial to the injury indicating capability of a dummy, it has a 9.8 kg near-side rib mass which is approximately an order of magnitude greater than that of the human, and it develops impact forces that are nearly three times higher than the recommended human chest response. It possesses characteristics primarily of an inertial device. The thoracic trauma index (TTI) was evaluated as an indicator of side impact injury risk, and design trends and optimized padding characteristics identified with the SID and TTI were compared with those from the Hybrid III dummy and viscous or compression injury criteria.

This paper presents a methodology to link reductions in biomechanical responses due to force-limiting material to projections of injury mitigation in real-world side impact crashes, and to use this approach to evaluate the potential injury reducing benefit for the chest and abdomen of constant crush force material in the side door and armrest. Using a simulation of the human impact response, a range in crush force was determined which effectively reduced a peak biomechanical response from that obtained with a rigid impact. The range in constant crush force depended on the velocity of impact. The higher the velocity of impact, the higher the level of crush force to achieve a reduction in the peak response. NCSS field accident data for car-to-car side impacts provided information on the occupant exposure and injury as a function of the change in velocity (ΔV) of the struck vehicle.

Role of the Seat in Rear Crash Safety addresses the historic debate over seatback stiffness, energy absorbing yielding, occupant retention and whiplash prevention; and it provides a scientific foundation for the direction GM pursued in the development and validation of future seat designs. It also describes the multi-year research study into the role of the seat in rear crash safety - first by addressing the need for occupant retention in the more severe rear crashes; and then by addressing the needs for an adequately positioned head restraint and changes in the compliance of the seatback to lower the risks of the whiplash in low-speed crashes.