The Effects of Seated Position on Occupant Kinematics in Low-speed Rear-end Impacts

Abstract

Seventeen rear-end impacts with a nominal 8 km/hr change in velocity to five human subjects in four positions were conducted. The four seated positions consisted of the Normal position, with the torso against the seat back, looking straight ahead, hands on the steering wheel, and feet on the floor; the Torso Lean position, with the torso leaned forward approximately 10 degrees away from the seat back; the Head Flex position, with the head flexed forward approximately 20 degrees from normal; and the Head Flex / Torso Lean position, with the head flexed forward approximately 20 degrees from normal and the torso leaned forward approximately 10 degrees from normal position. Relative to the Normal position, it was found that in both positions involving the torso lean, the peak head acceleration for the subject's head was reduced during the head-restraint impact.Further, the inertial acceleration of the head due to the forces on the neck, prior to the head rest impact, was somewhat higher for the two positions involving torso lean. Minor, transient, whiplash associated disorder (WAD) symptoms were noted. The nominal change in velocity used in this study appears to be of a reasonable magnitude to continue human subject out of position (OOP) testing.

A Comprehensive Review of Low-Speed Rear Impact Volunteer Studies and a Comparison to Real-World Outcomes

“…A complete collection of the available volunteer literature resulted in a dataset of 1984 total volunteer exposures from 51 individual studies. 5 – 10 , 12 , 15 – 18 , 22 – 26 , 28 – 32 , 34 – 41 , 43 , 46 – 54 , 56 – 59 , 61 – 64 , 66 – 68 , 73 On average, each study performed 40 tests with a range from 1 to 484 tests and used 51 subjects with a range of 1 to 65 volunteers per study. Many of the volunteers experienced more than one exposure (Figure 1 ).…”

“…Twelve studies reported head acceleration experienced by the volunteers. 5 , 15 , 23 , 26 , 30 , 32 , 37 , 38 , 40 , 59 , 67 , 68 These studies provide 125 data points for head acceleration as a function of vehicle change in speed (Figure 6 ). These points were fit to a polynomial and power trendline, which produced similar accuracy.…”

A Proposed Algorithm to Assess Concussion Potential in Rear-End Motor Vehicle Collisions: A Meta-Analysis

“…Although the scientific community is aware of a relation between head acceleration and delta-V, this relation is not quantitatively well understood. Other parameters, such as occupant position [14,15] or body mass index [16], have also been reported to affect head acceleration for a given delta-V, but quantification of the effect of those parameters has yet to be conducted. The poor quantitative understanding of the aforementioned relation can be explained by the challenging nature of conducting tests to collect such data.…”

The Vehicle’s Frontal Impact Influence on Driver in out of Position

“…Another research approach within this field focuses on the seated-position of the occupants. Thus, in [5], the peak head acceleration and the peak thorax acceleration have been compared to the normal position and the out-of-position (OOP), in order to establish the seated position consequences in low-speed rear-end impacts. Hence, the out of position and/or normal seated position of the occupants correlated to the operating mode of the airbag system make way to new analysis perspectives.…”