Stephen Cash; Mark Crouch
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Lecture
2015
24. EVU Conference, Edinburgh
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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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