Post-Collision Speedometer Readings And Vehicle Impact Speeds

This paper investigates the appropriateness of using the residual post-collision speedometer reading as an indicator of vehicle speed at impact. The study reviews the history of crash evidence involving speedometers, crash test results, exemplar instrument clusters and case studies in which the post-collision speedometer readings are compared to those obtained by traditional accident reconstruction techniques. Findings show that a non-zero post-collision speedometer reading may or may not coincide with that vehicle’s approximate speed at impact. In case studies, the residual speedometer reading did not usually represent that vehicle’s speed at impact. This finding reinforces the observation that the readings of most unpowered exemplar instrument clusters could easily be altered with vibration or changes in orientation. Based on these findings, it is not recommended that post-collision speedometer readings be included in a reconstruction as evidence of that vehicle’s speed in most cases. However, some vehicles are equipped with instruments whose indicator needles demonstrate an increased resistance to movement combined with a lower susceptibility to needle motion during orientation, vibration and shock changes. With these vehicles, residual speedometer reading could cautiously be used as corroborative evidence in some accident circumstances.


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  • Accession Number: 01337632
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 25 2011 7:03AM