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Recently, it has been demonstrated experimentally that the so-called “whiplash” response during low velocity rear-end collisions may produce a spontaneously resolving strain injury to muscles of the neck, but that injury to other spinal elements is biomechanically improbable. This paper reviews the results of these studies as a means of addressing the longstanding controversy which surrounds “whiplash” and the claims that the “whiplash” response produces more extensive injuries. It is concluded that there are no objective, experimentally-based scientific data to support the concept that the low-velocity “whiplash” response is capable of producing any injuries beyond those to the cervical musculature.

Predictions of occupant motion in passenger vehicles undergoing rollovers have been hampered by the uncertainties of the vehicular motion. These uncertainties arise due to a host of factors which may be difficult to quantify, such as trip conditions, vehicle/terrain interaction dynamics and mass eccentricities. In this paper the initial segment of a roll sequence of high angular velocity (greater than 4 radians per second) about a longitudinal axis is examined. The resultant unrestrained motions of the near and far side occupants are studied. To facilitate this analysis a mathematical model has been developed which incorporates dynamic characteristics of the occupant, the vehicle and the terrain surface. The analysis is carried through the first significant vehicle/ground impact following roll initiation. Occupant kinematics are described.

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 restitution or rebound that occurs as the final phase of a vehicle-to-vehicle collision is quantified by the coefficient of restitution, which is the ratio of the closing velocity to the post-impact separating velocity of the two colliding vehicles. The coefficient of restitution of medium and high velocity collisions is low, [approximately 0.1] since these collisions are quite inelastic, whereas collisions at extremely low velocities are relatively elastic with the coefficient of restitution theoretically approaching 1.0. However, the actual collision restitution magnitude in the low velocity range has not been adequately established. A series of vehicle-to-vehicle and vehicle-to-barrier collisions resulting in velocity changes in the 2 to 5 miles per hour range was conducted in which vehicles with various bumper configurations [factory standard equipment] were utilized to study the coefficient of restitution at low closing velocities.

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.