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The risk of sustaining injury in rear impact collisions is correlated to collision severity as well as other factors such as restraint usage. The most recent National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) data available (1997 to 2011) were analyzed to identify accidents involving passenger vehicles that have experienced an impact with a principal direction of force (PDOF) between 5:00 and 7:00, indicating a rear impact collision. The Abbreviated Injury Scale (AIS) was used as an injury rating system for the involved vehicle occupants who were at least sixteen years old and were seated in the outboard seating positions of the front row. These data were further analyzed to determine injury risk based on resultant delta-V and restraint system use. Each body region (head, spine, thorax, abdomen, upper extremity, and lower extremity) was considered separately.

Low-speed collisions between tractor-semitrailers and passenger vehicles may result in large areas of visible damage to the passenger vehicle, but often produce limited damage to the tractor-semitrailer. Despite this, such accidents may lead to assertions of serious injury to the tractor driver and/or sleeper compartment occupant. Research regarding the impact environment and resulting injury potential of the occupants during these types of impacts is limited. This research investigated driver and sleeper compartment occupant responses to relatively low-speed and low-acceleration impact events. Five crash tests involving impact between a tractor-semitrailer and a passenger car were conducted. The test vehicles were a van semitrailer pulled by a tractor and three identical mid-sized sedans. The occupants of the tractor included a human driver and an un-instrumented Hybrid III 50th-percentile-male anthropomorphic test device (ATD).

Low-speed sideswipe collisions between tractor-semitrailers and passenger vehicles may result in large areas of visible damage to the passenger vehicle. However, due to the extended contact that occurs during these impacts, it is typical in these incidents for the crash pulse duration to be long and the vehicle accelerations to be correspondingly low. Research regarding the impact environment and resulting injury potential of the occupants during these types of impacts is limited. Five full-scale crash tests utilizing a tractor-semitrailer and a passenger car were conducted to explore the occupant responses during these types of collisions. The test vehicles included a van semitrailer pulled by a tractor and three identical mid-sized sedans. The occupants of the sedans included an instrumented Hybrid III 5th -percentile-male anthropomorphic test device (ATD) in the driver's seat and an un-instrumented Hybrid III 5th -percentile-female ATD in the left rear seat.

Debate surrounds the utility of the Biofidelic Rear Impact Dummy (BioRID) anthropomorphic test device (ATD) for providing meaningful biomechanical metrics during rear impact and the appropriate criteria for interpreting the ATD response. In the current study, we performed a comparison of the kinematic and kinetic responses of the BioRID II and Hybrid III ATDs over a range of low- and moderate-speed rear impact conditions. A BioRID II and a midsize male Hybrid III were tested side-by-side in a series of rear impact sled tests. To evaluate occupant response in rear impact, the ATDs were positioned into front row standard production bucket seats, restrained by 3-point safety belts, and subjected to rear impacts with delta-Vs (ΔVs) of 2.2, 3.6, 5.4, and 6.7 m/s (5, 8, 12, and 15 mph).

Previous studies have suggested injury assessment reference values (IARVs) for lower neck injury based on scaled upper neck values. This study developed independent flexion and extension IARVs for the lower neck by matching Anthropomorphic Test Device (ATD) data to impact-tested post-mortem human subjects (PMHSs) with mid- to low-cervical spine injuries. Pendulum and sled tests with Hybrid III midsize male and small female ATDs were run under conditions mimicking those of published PMHS torso drop-sled tests and other PMHS studies. Measurements included upper and lower neck forces and moments, head acceleration, head rotation rate, and head/neck angles for the pendulum tests. Rear impacts corresponding to rigid seatback tests without a head restraint produced lower neck extension moments that increased dramatically with test severity, as measured by increasing delta-V and/or decreasing pulse duration.

Police accident reports (PARs) of motor vehicle collisions typically include information regarding occupant restraint use. It has been suggested that PARs overestimate restraint use. Previous studies comparing PAR restraint usage with that determined during a NASS/CDS in-depth investigation found agreement in approximately 90% of cases. The accuracy of PAR-reported restraint usage for outboard vehicle occupants was compared to that determined by NASS/CDS investigators as a function of injury severity and crash type. Restrained occupants were more likely to be identified correctly in the PAR, and unrestrained occupants were more likely to be accurately identified as injury severity increased. Differences in the accuracy of PAR-reported restraint usage rates for different crash types were small.

Accident investigators are often required to determine if an occupant was using a seat belt during a collision. Substantial research has been conducted on the types of physical evidence generated on a seat belt by occupant loading during a collision. However, very little research has been conducted concerning the characteristics of physical evidence that is created when an occupant uses their seat belt improperly. Case studies with misused seat belts were reviewed showing tell-tales of atypical or improper restraint usage. Occupants also experienced injuries consistent with greater excursion and contact with vehicle interior surfaces. To compare the physical evidence of properly and improperly used restraints, automotive frontal sled tests were conducted with matched pairs of anthropomorphic test devices (ATD) with seat belts used both correctly and incorrectly. When the seat belt was used improperly, distinctly different marks were observed.

In rollover accidents, physical evidence of seat belt usage is occasionally difficult to discern. Typically, if a seat belt is used by an occupant in an accident, various seat belt components will display characteristic marks in well-defined locations. These marks are known as “witness marks” or “occupant load marks.” Witness marks in a rollover accident may be faint in comparison to those caused by the occupant restraint forces in high-energy planar collisions. Additionally, in situations where a seat belt buckle is alleged to have unlatched early in a rollover accident, the lack of clear occupant load marks may in some cases be attributed to an alleged “buckle release” that occurred very early in the rollover sequence, so that the seat belt did not sustain loading while in a latched condition.

When an automotive seat belt buckle is believed to have released during a motor vehicle accident, it is typically attributed to one of several potential mechanisms, including inertial release, partial engagement, inadvertent contact, or structural overload. While the majority of literature in the past has focused on the topic of inertial release, little has been written on other release mechanisms. This review paper addresses automotive seat belt buckle release by inadvertent contact between the buckle pushbutton and some other object. This paper describes the conditions that must be satisfied for inadvertent contact to result in buckle release, including release force, direction, and pushbutton travel. We explain the role of occupant kinematics and the likelihood of contact between and occupant's hand or arm and the pushbutton. Occurrences of inadvertent contact in safety testing and a real world case study are presented.

Accident investigators are often required to determine if an occupant was wearing their seat belt during a collision. Previous studies have provided examples of physical evidence relied upon by investigators to determine if the seat belt assembly was subjected to occupant restraint loading. This paper examines the potential for clothing fibers to be permanently transferred to the seat belt webbing during a collision. To evaluate fabric transfer evidence as an indicator of restraint usage by an occupant during a collision, the following issues were examined: automotive seat belt webbing construction and behavior under load, fiber evidence found on the webbing in new and used conditions, and the transfer of different types of clothing fibers to webbing during full-scale sled testing.

The results of a number of previous studies have demonstrated that seat-belted occupants can undergo significant upward and outward excursion during the airborne phase of vehicular rollover, which may place the occupant at risk for injury during subsequent ground contacts. Furthermore, testing using human volunteers, ATDs, and cadavers has shown that increasing tension in the restraint system prior to a rollover event may be of value for reducing occupant displacement. On this basis, it may be argued that pretensioning the restraint system, utilizing technology developed and installed primarily for improving injury outcome in frontal impacts, may modify restrained occupant injury potential during rollover accidents. However, the capacity of current pretensioner designs to positively impact the motion of a restrained occupant during rollover remains unclear.

Lateral head motions, torso motions, lateral neck bending angles, and electromyographic (EMG) activity patterns of five human volunteer passengers are compared to lateral motions of a Hybrid III ATD during right-left and left-right fishhook steering maneuvers leading to vehicular tip-up. While the ATD maintained relatively fixed lateral neck angles, live subjects leaned their heads slightly inward and actively utilized their neck musculature to stiffen their necks against the lateral inertial loads. Except for differences in neck lateral bending, the Hybrid III ATD reasonably reflects occupant kinematics during the pre-trip phase of on-road rollovers.

Detailed investigations continually demonstrate that vehicle collision environments are extremely unlikely to produce accelerations of sufficient magnitude and duration to cause inertial release of seat belt buckles. Recently, it has been proposed that the dynamic response of an end-release buckle mounted to the vehicle structure via a metal strap or wire rope can amplify acceleration levels experienced at the floor of the vehicle by a factor of 10 or more, to levels that are high enough to cause inertial release. Experiments and modeling presented here confirm that accelerations may be amplified from the floor of the vehicle to the seat belt buckle, but not by more than a factor of 1.3, and only for acceleration pulse durations that are very short. Shock table testing of end-release seat belt buckles shows that, even with amplification, the resulting buckle accelerations are far below those required to cause inertial release, even at very low webbing tension.