EVU XXIV 2015-21 Calculating Vehicle Speed from Yaw Mark Analysis

Calculating Vehicle Speed
from Yaw Mark Analysis
Stephen Cash
Mark Crouch


Investigating a crash where a vehicle has left curved tyre marks is a relatively
common occurrence for a Collision Investigator. Much research surrounding the
subject has provided criteria that once met, allows a vehicle’s speed to be
calculated. This paper examines the validity of conventional principles, and
presents an alternative approach that can be used in many collisions where current
criteria may not be satisfied. This paper outlines, from basic principles, the current
methodology of calculating a vehicle’s speed from a curved tyre mark and goes on
to examine the forces introduced by vehicle yaw and braking. By understanding
centripetal motion, ‘critical speed’, and braked and rotating vehicles, it then
provides an expression to calculate vehicle speed where the range is both narrow
and stable, with a narrower error band than conventional methods.

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AutoreStephen Cash - Mark Crouch
Pubblicato il