Risk of concussion due to head acceleration in rear impact sled tests of passenger automobile seats

Abstract

Objective: Acceleration-based injury metrics can be useful for quantitatively evaluating risk of concussion (a form of mild traumatic brain injury, or mTBI) after automobile collisions, especially when objective medical findings may be negative, as in many cases of concussion. In the present study, head acceleration data were used to evaluate the risk of concussion or more serious head injury to the driver of an automobile that experiences a rear impact resulting in a forward change in velocity (delta-V) of 15.5 km/h (9.6 mph).Methods: Data were collected from 34 Insurance Institute for Highway Safety (IIHS) rear impact sled tests conducted from 2009 through 2017 for driver seats from 10 passenger car models leading in U.S. sales in 2017. Resultant translational head acceleration data were used to compute the head injury criterion (HIC; HIC15, HIC36) and A-3ms (the 3-ms resultant acceleration criterion utilized by the European New Car Assessment Protocol and others), and maximum resultant translational acceleration (aT). Maximum resultant rotational acceleration (aR) was estimated based on Biofidelic Rear Impact Dummy (BioRID) data from Welch et al. (2010).Results: No sled test included in the study resulted in a HIC15 value exceeding 55, a HIC36 value exceeding 85, A-3ms exceeding 28 g, aT exceeding 28 g, or estimated aR exceeding 1,400 rad/s2. These values are far below published automotive injury risk values (IARV) used to evaluate crashworthiness. Further, contemporary concussion risk curves place the HIC15, aT, aR, and paired combination of aT and aR sustained by the BioRID anthropomorphic test dummy (ATD) in the IIHS tests at a negligible risk of concussion (mTBI).Conclusions: The 15.5 km/h delta-V IIHS rear impact sled tests conducted between 2009 and 2017 for common passenger automobile driver seats resulted in injury metrics associated with minimal risk of concussion or more severe head injuries.