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An Examination of Equations Relating Motorcycle Impact Speed to Struck Vehicle Post-Impact Rotational Displacement
Abstract:
When a motorcycle collides with a passenger vehicle, the impact can cause a change in the translational and rotational velocities of the struck vehicle. If these velocity changes, or the magnitude of the translation and rotation of the struck vehicle can be quantified, then these can potentially be used to calculate the impact speed of the motorcycle. There are several methods that could be used for this analysis. The most general and comprehensive solution will be to use one of the widely-accepted accident reconstruction simulation programs - PC-Crash, HVE (the EDSMAC4 or SIMON modules), Virtual CRASH, or VCRware. However, these simulation programs can be time-consuming to apply and not everyone has access to them. It would be useful to have simple formulas for obtaining a reasonable estimate of the motorcycle impact speed based on the observed post-impact translation and rotation of the struck vehicle. All the more useful if a method could be based on the struck vehicle rotation alone. And, in fact, several such methods exist in the literature.
This paper tests these methods for obtaining an initial estimate of a motorcycle’s impact speed based on the struck vehicle’s post-impact rotation alone. The accuracy of the methods is assessed and the sensitivity of the methods to various parameters are discussed. This paper demonstrates that the initial translational velocity of the struck vehicle significantly affects the magnitude of the struck vehicle’s post-impact angular displacement. Thus, methods that consider both the translation and rotation of the struck vehicle are more accurate than methods that rely on the struck vehicle rotational displacement alone.