Occupant Protection / Restraints

Exponent’s engineers and scientists have unmatched experience and capabilities related to occupant protection and restraint systems. We research and publish regularly on a wide array of occupant protection topics, and we work closely with our vehicle engineering practice to maintain an up-to-date knowledge base concerning restraint technology. Our approach combines comprehensive documentation and evaluation of physical evidence with surrogate evaluations; physical testing, ranging from static roll demonstrations and airbag deployments to sled simulations and full-scale crash testing; human motion modeling and simulation; and review of relevant field accident data and literature to assess occupant protection concerns. Applications include investigation of accidental injury and support for design review of new or modified occupant protection systems.

Active Restraints — Manual Seat Belts

Exponent has extensive experience in evaluation of seat-belt systems and their relationship to occupant protection and injury mitigation. Key areas of investigation include evaluations of seat-belt geometry, fit and performance, effectiveness, occupant excursion, partial or complete ejection, and possible allegations of seat belt non-use or misuse, in a variety of accident scenarios. We have published studies and continue ongoing research into claimed seat-belt failure mechanisms, including inertial unlatching and inadvertent release, and the resulting physical evidence and occupant entanglement and injury characteristics.

Figure 1. Illustration of occupant excursion with and without seat belt during angled frontal impact.

Passive Restraints — Airbags and Related Systems

We evaluate and analyze issues related to airbag systems, including frontal, side, and side curtain (rollover) systems. Areas of investigation include deployment timing and envelope relative to occupant kinematics, airbag safety and effectiveness for different crash modes, and airbag-induced injury, including issues related to airbag interaction with unbelted or out-of-position occupants. We are also experienced with other passive systems such as automatic seat belt systems.


Figure 2. Surrogate demonstrating how an out-of-position occupant’s head can bypass an inflated airbag during frontal impact. The occupant’s injury pattern and this position were correlated with physical evidence on the accident seat belt (not illustrated), which indicated more seat belt webbing was extended than would be utilized for an in-position driver.

Child Restraint Systems

Combining our extensive experience and knowledge of pediatric biomechanics and restraints, Exponent’s engineers and scientists evaluate a broad spectrum of concerns related to child restraints. We are familiar with all types of child restraints available, including infant-only, rear-facing, forward-facing, convertible, and various types of booster seats, and have performed research studies on the performance of such systems in crash environments. Exponent evaluates child restraint fit, performance, proper usage, effectiveness, testing, and interaction with other restraint-system elements, such as adult seat belts and LATCH systems.


Figure 3. Dynamic testing of child restraint system.

Other Occupant Protection

Many other elements of a vehicle’s interior are involved in providing protection to the occupant during an accident. Our staff provides the necessary expertise to evaluate the complex interactions of an occupant with such elements as head restraints, seatbacks, steering wheels, and other interior structures, such as knee bolsters, door beams, footwells/controls, consoles, and trim panels. Other issues evaluated include the relative safety of various seating positions in a given accident (e.g., rear-seat safety for child occupants), the effect of unrestrained occupants or cargo on restrained-occupant injury potential, and the performance of rollover protection systems (ROPS) in applicable vehicles.

Restraint Technology

Exponent’s consultants have the background and research experience to evaluate the occupant protection issues related to current, alternative, and advanced technological developments in restraint systems, including seat-integrated restraints, energy-management systems, pretensioners and motorized tensioning systems, head restraints, occupant position-sensing and classification systems, and event data recorder (EDR; “black box”) restraint status information.



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