Citation

Bergh P. Collision 2009; 4(1): 40-43.

Copyright

(Copyright © 2009, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

There are three common approaches for calculations of speed from a set of locked wheel skid marks of unequal length. In the first, the length of the longest skid mark is used in the standard skid formula. In the second approach, the average length of the skid marks is used in the standard skid formula. The third approach involves splitting the calculation into several steps, where each step of the calculation involves different braking efficiencies but equal length skid marks, using the standard skid formula in each step, and calculating a speed loss from each step. The speed losses are then combined from all speeds into one speed loss for the skid length. Although all three approaches give similar results when the lengths of the skid marks are close to each other, the first two approaches give incorrect results when the lengths of the skid marks vary widely. This article recommends against using the first two approaches and presents a simple formula to use when the lengths of the skid marks vary widely.