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Accident investigators rely on a wide range of methods to measure or quantify vehicle braking deceleration. Generally, this information is applied to define a “drag factor” or “coefficient of friction” for a skidding vehicle. Methods employed can include everything from simple estimations based on past experience and individual expertise to testing using sophisticated devices. This paper is a compilation of data from a series of skid tests comparing some of the methods and equipment currently available. These tests were performed with an assortment of vehicles each equipped with or monitored by a selection of devices designed/applied to quantify some combination of time, distance and velocity. The devices tested include two models of “fifth wheels,” the Vericom VC2000, the g-analyst, a bumper detonator and shot timer, doppler RADAR, an infrared timer device, and a drag sled. The data from each of these skid tests is then provided for the reader's comparison and analysis.

After an accident has occurred, there are a minimal number of low speed crash tests to assist the accident reconstructionist/engineer in determining the speed of a vehicle from little or no visible vehicle damage. Injuries are being documented by individuals as occurring in relatively low speed collisions. Yet, the impact speeds that have been taught to cause little or no damage do not suggest that injuries should have occurred at these correspondingly low G-forces. No comparison of the injury versus vehicle speed will be done in this paper; that is left to the biomechanical engineers and physicians. The purpose of this paper is to examine the issue of low speed impacts and the corresponding damage or shock isolator movement to the vehicle. For the purpose of this paper a low speed collision is an in line impact at a speed below 6 m/s.