The influence of seatback characteristics on cervical injury risk in severe rear impacts

The determination of the optimum seatback characteristics for the mitigation of serious and catastrophic neck injury during high-speed rear-end collisions remains a topic of continued investigation. Despite a number of prior research efforts, both field data and sled test studies have yet to define a single optimal seatback performance criterion. Further, recent developments in seatbacks have introduced new designs into the field that have not been compared to more traditional designs. Analysis of NASS data from 1980 to 1999 demonstrated that at changes in velocity (DeltaV) above 40 kph, rear-end collisions have a dramatically lower risk for catastrophic injury than frontal, near-side or far-side impacts. Unfortunately, owing to the small penetration of newer seatback designs in the automotive fleet, it is not possible to examine the influence of seatback design parameters on serious neck injury using these data alone. Accordingly, seven rear impact HYGE sled tests were conducted using a wide range of seat designs. Upper and lower neck load cells were used to measure neck forces and moments in restrained 50th male Hybrid III anthropomorphic test devices (ATD). Additionally, the neck injury criteria (Nij) was computed. Unlike prior studies that have examined the standard seated ATD or the dramatically out-of-position ATD, these tests were conducted using an ATD seated in non-standard but typical driving position. The results of this study indicate that several descriptions of seatback behavior, such as quasi-static ultimate force are poor predictors of ATD neck loading. It also suggests that, for the severe crash studied, an optimum range of seatback stiffness exists, which appears to be in the mid-range of seatback stiffnesses available in current production vehicles. These data continue to illustrate the complex relationship of seatback design parameters to neck injury risk.