Biofidelity Evaluation of THOR-50M in Rear-Facing Seating Configurations Using an Updated Biofidelity Ranking System

Vehicles with automated driving systems (ADS) may allow nontraditional seating arrangements, such as a reclined seat that is rear facing in a frontal impact. Currently, there is not a widely accepted, commercially available, anthropomorphic test device (ATD) that is designed for a reclined, rear-facing, high-speed crash situation. To begin to identify what modifications are needed for candidate ATDs to exhibit human-like characteristics in these nontraditional scenarios, ATDs should be tested and compared to available postmortem human subject (PMHS) biofidelity response corridors in these seating arrangements. The first objective of this study was to present and discuss updates to the Biofidelity Ranking System (BRS). The second objective was to use the updated BRS to evaluate the responses of the THOR 50th percentile male (Test device for Human Occupant Response, THOR-50M) ATD in the rear-facing condition. Quantitative comparisons were made between the THOR responses and biofidelity corridors obtained from matched pair PMHS 56 kph tests at 25° and 45° seatback recline angles utilizing a rear impact sled buck; the occupant seats were supported by an instrumented, rigidized structure to prevent seatback/head restraint motion and measure occupant loads applied to the seat. BRS scores revealed that the THOR has a more biofidelic average occupant response at 45° than at 25° recline, and a better average seat loading biofidelity score at 25° compared to 45° recline. Injury prediction results were mixed in how well THOR-50M measurements align with PMHS injuries. Revisions to THOR would be necessary to produce more realistic vertical spinal motion to match the PMHS head and pelvis kinematics in a reclined seat.