Aggregation of Cervical Loads in Rear Impact Crash Tests and Comparison to Activities of Daily Living

Peak upper and lower neck load data from rear impact crash testing were reviewed, aggregated, and analyzed from over 1,800 tests of existing peer-reviewed literature and research as well as available testing conducted by the Insurance Institute for Highway Safety (IIHS) and the National Highway Traffic Safety Administration (NHTSA). Both human volunteers and anthropomorphic test devices (ATDs) were subjects of the reviewed studies and testing. Peak upper and lower neck axial forces (compression and tension), sagittal shear forces, and sagittal moments (flexion and extension) from available crash testing were reported and analyzed as functions of measured change in velocity (delta-V) ranging from approximately 3 to 60 km/h (1.9 to 37 mph). This load data was then further analyzed for possible trends amongst various testing conditions, such as seat type, ATD used, and subject seating position within the vehicle chassis and seat. The linear regressions developed from rear impact crash testing suggest that a relationship does exist between peak cervical spine loading and delta-V. For the upper neck, peak tension and extension showed the strongest correlations with respect to delta-V, seen in their calculated R2 values of 0.37 and 0.30, respectively. Similarly for the lower neck, peak tension and extension showed the strongest correlations with respect to delta-V, with R2 values of 0.48 and 0.46, respectively, while peak compression had the lowest correlation (R2 = 0.07). The same cervical spine loads were also aggregated from studies that measured loading in various activities of daily living (ADLs), such as everyday tasks and activities typically undergone by amusement park patrons and athletes. The analyzed ADLs produced cervical spine loading that was greater than the aggregated data from crash testing and sled tests that underwent delta-Vs of less than approximately 24 km/h (15 mph). The data suggests that participants of related everyday activities may undergo peak cervical spine loading similar to what is experienced by normally seated occupants in lower-speed (delta-V less than 24 km/h (15 mph)) rear impact motor vehicle collisions.