The Traffic Accident Reconstruction Origin -ARnews-

Re: Rotating Vehicles Drag Factor

Bill Houston (CARSINCORP@MSN.COM)
Sun, 9 Mar 1997 22:46:18 -0500 (EST)

Dear Mr. Borchers;

Rudolph Limpert addresses a method for determining speed from a spinning vehicle in his book, "Motor Vehicle Accident Reconstruction and Cause Analysis," 1989, The Michie Company, pgs 225-229. He references it as a speed calculation from spin marks. In short, he plots the path of the vehicle's center of mass and utilizes the heading angles to determine the disipated energy between several points along the vehicle's path to final rest. By using a straight line distance and 75% of the full drag factor, the calculated answer is within 2/10 MPH of his example. I have utilized his method in two additional cases where there was enough physical evidence to calculate a speed and have compared it with a 75% use of a full drag factor. In both instances, byusing a straight line distances and using 75% of full drag factor, the calculated speeds are within 1-2 MPH of each other. I don't know if that is the precision you require but it seems that you would be safe in using 70-75% of the full drag
factor.

I hope this information is of some value to you.
Bill Houston
CARSINCORP@MSN.COM

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