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The formula used to compute the drag factor is as follows: the drag factor equals the known speed of the test vehicle squared, divided by the result of the constant of thirty times the distance of the longest skid in feet. The vehicle used as the test vehicle should be a car of equal size and weight as to the car that crashed or if possible the crash vehicle itself, more often it is likely to be your police cruiser.

The formula to compute the minimum speed of the crash vehicle is as follows: The minimum speed of the test vehicle equals thirty times the distance of the average of the skid lengths, times the drag factor, times the percentage of braking efficiency, i.e., which tires left a skid. The square root of the above product is then taken to determine the mimimum speed of the crash vehicle in miles per hour when it entered the skid. The braking efficiency used is based on the Society of Automotive Engineers Technical Paper #830612 which was provided by the Ohio State Highway Patrol.