Citation

Bartlett W, Schmidt B. Collision 2010; 5(2): 108-111.

Copyright

(Copyright © 2010, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The so-called "cone of departure rule" is the notion that when two vehicles collide, their departure vectors must fall within the cone formed by their approach vectors. Although accident reconstructionists often use this rule, it is merely a common observation rather than an inviolable law of motion. This article describes a crash test that was conducted to demonstrate that the cone of departure rule is not always true. The crash test involved a slow-moving pickup truck and a tractor-trailer accelerated to the highest possible speed on the longest approach available. After impact, the truck rotated counterclockwise and was pushed to the left of the tractor-trailer, while the tractor trailer's trajectory was redirected slightly right. A conservation of linear momentum analysis was undertaken using measured values and incorporating appropriate ranges. Findings showed that the truck's departure angle was approximately 4.3 degrees outside of the cone defined by the approach vectors for the two vehicles. These findings confirm that vehicles involved in a collision can depart from the cone defined by their approach angles when the momentums between the two vehicles are significantly different.