Optimizing frontal impact occupant protection systems for passengers seated in wheelchairs.

OBJECTIVE: The advent of automated vehicles (AVs) provides an opportunity to design integrated wheelchair seating stations that provide an equivalent level of safety for occupants using wheelchairs as those using vehicle seating. This study designed a frontal occupant protection system for an integrated second-row wheelchair seating station that includes optimized airbags and seatbelt systems. METHODS: MADYMO models were used to optimize belt geometry for a midsized male ATD seated in a surrogate wheelchair fixture, with and without inclusion of a Self Conforming Rearseat Air Bag (SCaRAB). Sled tests were performed to confirm the benefits of airbag use and optimized belt geometry. Additional modeling was performed with commercial manual and power wheelchairs, to identify the effects of wheelchair design and forward clear space on occupant kinematics and injury measures. Additional sled tests were performed with manual and power wheelchairs to demonstrate effectiveness of the restraint system with commercial products. RESULTS: Simulations and tests both showed improved kinematics using an optimized seatbelt system geometry compared to a commonly used suboptimal D-ring location that places the shoulder belt at a more outboard location. Use of the SCaRAB helped compensate for suboptimal geometry. Results include specific recommendations for belt geometry relative to the wheelchair seating station and airbag parameters suitable for protecting occupants seated in wheelchairs. Restraint systems initially optimized using the surrogate wheelchair also performed well with the two commercial wheelchairs. The clear space required for maneuvering a wheelchair will likely prevent injurious head contact in frontal crashes. CONCLUSIONS: This study is the first to design a frontal optimal occupant protection system for an integrated second-row wheelchair seating station, demonstrating that it should be feasible once integrated wheelchair seating stations are included in AVs.

A Literature Review of Wheelchair Transportation Safety Relevant to Automated Vehicles.

This literature review summarizes wheelchair transportation safety, focusing on areas pertinent to designing automated vehicles (AVs) so they can accommodate people who remain seated in their wheelchairs for travel. In these situations, it is necessary to secure the wheelchair to the vehicle and provide occupant protection with a Wheelchair Tiedown and Occupant Restraint System (WTORS). For this population to use AVs, a WTORS must be crashworthy for use in smaller vehicles, able to be used independently, and adaptable for a wide range of wheelchair types. Currently available WTORS do not have these characteristics, but a universal docking interface geometry and prototype automatic seatbelt donning systems have been developed. In the absence of government regulations that address this situation, RESNA and ISO have developed voluntary industry standards to define design and performance criteria to achieve occupant protection levels for wheelchair-seated passengers that are similar to those provided by conventional vehicle seats.

Dynamic metrics to differentiate booster performance.

OBJECTIVE: The purpose of this research was to explore candidate booster performance metrics that may have the potential to identify less effective booster systems, because current FMVSS No. 213 booster performance requirements can be met without a booster. METHODS: To provide a more realistic test environment, dynamic testing was performed using a surrogate seat belt retractor on the most recent preliminary design update proposed for the FMVSS No. 213 seat assembly. Given that field data show that belt-positioning boosters are effective at reducing injury risk, potential testing measures were assessed relative to data collected for the no-booster condition. Eleven booster products were evaluated, as well as the no-booster condition, with 6 tests performed using the Hybrid III 10-year-old and 33 tests run with the Hybrid III 6-year-old. RESULTS: Possible metrics associated with good anthropomorphic test device (ATD) kinematics (no submarining or rollout) were the difference between knee and head excursion, maximum torso angle, lumbar spine Moment Z, and lumbar spine Force Y. CONCLUSIONS: When testing boosters under more realistic dynamic conditions, the proposed metrics would allow better discernment of less effective boosters, because they differentiate performance relative to the no-booster condition.