Passenger Kinematics During Crash Avoidance Maneuvers

Abstract

Abrupt vehicle maneuvers that occur before a crash can affect occupant postures and may influence the level of protection provided by the occupant protection systems. Previous research has shown that occupant responses to on-road maneuvers have high variability, but the sample sizes have been too small for robust analysis of the potential effects of occupant characteristics such as age and body size. In addition, some studies have also suggested that participant awareness affects the magnitude of responses. To address these gaps, 87 men and women with a wide range of body size and age were recruited for a test track study. The purpose of the study was obfuscated somewhat by telling the participants that the study was focused on vehicle ride and handling. Testing was conducted at the University of Michigan's Mcity facility with the participants riding in the front passenger seat of a late-model sedan. Detailed anthropometric data were obtained from each participant, including 3D body scans. Vehicle motions were recorded with an inertial measurement unit and passenger head motions were tracked using a novel system based on a Microsoft Kinect sensor. During a short drive around the Mcity facility, participants answered questions about the vehicle ride until a they experienced an unaware, maximal braking event from 56 kph that peaked at approximately 1 g and lasted about 2 seconds. After the drive resumed, the participants experienced a sharp right turn with maximal braking, an abrupt lane change, and another maximal braking event. Based on video of facial reactions, nearly all participants were surprised by the first braking event. The mean (standard deviation) of excursion of the estimated head center of gravity (CG) location in the first braking event was -135 (62) mm. The head CG excursion in the second braking event of -115 (51) mm was significantly less than in the first, but the difference was small relative to the within-condition variance. Head excursion on the second braking trial was less than on the first trial for 69% of participants. The maximum inboard head excursions in lane-change and right-turn maneuvers were -118 (40) mm and -131 (35) mm, respectively. Forward head excursions in braking were significantly smaller for older passengers and those with higher body mass index, but the combined factors accounted for less than 25% of the variance. Inboard head excursion in the lane-change event was significantly related to stature, but only about 7% of variance was related to body size. Head excursions for men and women did not differ significantly after accounting for body size. Global head angle changes during the events were generally smaller than 10 degrees and driven primarily by voluntary responses. Functional analysis methods were used to generate prediction corridors that can be used to tune and validate active human body models that are intended to simulate passenger response to pre-crash maneuvers. Future work should include a wider range of pre-crash posture and belt fit.