Some Aspects of Motorcycle-Vehicle Collision Reconstruction

A major difficulty in the reconstruction of motorcycle-vehicle collisions derives from the fact that the motorcycle-rider and the motorcycle itself execute in general different trajectories after a collision with another vehicle. Accordingly, certain assumptions which may vary from case to case have to be introduced in order that the momentum and energy balance approach which is usually applied for the purpose of collision reconstruction can be adapted to calculate pre-impact circumstances. However, due to the often unfavourable mass ratio an accurate reconstruction may be impeded. A problem also exists in the assessment of post-crash decelerations of motorcycles because their motion patterns during that phase are often complex and not easily reconstructed. Likewise, in determining the course of pre-impact braking it has to be taken into account that in most motorcycles front and rear wheel brakes are applied independently. According to whether, e.g., a fall of a motorcycle is caused by a skidding front or rear wheel the relative trajectories of motorcycle and rider may differ decisively.

On the basis of real motorcycle-vehicle collisions which were reconstructed for forensic purposes, possible reconstruction procedures are demonstrated. The application of momentum balance in combination with appropriate approximations to determine pre-impact speeds is elaborated. The importance of a reliable accident documentation thereby becomes evident. Furthermore, motorcycle braking and falling characteristics as well as some aspects of accident causation are discussed.