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A second series of low speed rear end crash tests with seven volunteer test subjects have delineated human head/neck dynamics for velocity changes up to 10.9 kph (6.8 mph). Angular and linear sensor data from biteblock arrays were used to compute acceleration resultants for multiple points on the head's sagittal plane. By combining these acceleration fields with film based instantaneous rotation centers, translational and rotational accelerations were defined to form a sequential acceleration history for points on the head. Our findings suggest a mechanism to explain why cervical motion beyond the test subjects' measured voluntary range of motion was never observed in any of a total of 28 human test exposures. Probable “whiplash” injury mechanisms are discussed.

The head motions of a human driver and a Hybrid III Anthropometric Test Device (ATD) right front passenger were measured in low-speed rearend impacts (velocity change (ΔV) ≤ 8 kph) with high speed film and accelerometers. Data were analyzed from three crashes with the same human driver (weight similar to ATD) at ΔV's of 3.9, 6.6 and 7.8 kph. The results indicate that the human's and ATD's head have roughly similar basic patterns of motion: a post-impact period where the head is stationary with respect to the earth (Phase I), a period where the head rotates rearward with respect to the vehicle (Phase II), a subsequent period where the head rotates forward with respect to the vehicle (Phase III) and a final period where the head settles into a post-impact rest position (Phase IV). The human's head motion tended to be more complex than the ATD's head motion during Phases II and III.

The head, neck and trunk kinematic responses of four volunteer test subjects, recorded during a series of experimental low velocity motor vehicle collisions, have been measured and analyzed. Using data obtained from multiple high speed film, video and electronic accelerometer measurements of the test subjects, it was found that the actual kinematic responses of the human head, neck and trunk that occur during low velocity rearend collisions are more complex than previously thought. Our findings indicate that the time-honored description of the cervical “whiplash” response is both incomplete and inaccurate. Although the classic “whiplash” neck response to rearend collisions and the widely accepted hyperextension/hyperflexion cervical injury mechanism have been extensively written and speculated about, there have been little human experimental data available, especially for low velocity collisions.