The Trajectories of Pedestrians, Motorcycles, Motorcyclists, etc., Following a Road Accident

For many years accident investigators have been faced by the problem of estimating the projection velocity associated with a given trajectory. The most recent contributions to this topic were two papers at the 1981 AAAM but these, like earlier work, deal only with the aerial part of the trajectory, until the object first lands. In most accidents however the point of first landing cannot be determined and it is the point at which the object comes to rest which is recorded.

The present paper derives an equation for the projection velocity associated with a given total trajectory. Using this equation it is possible to bracket the limits within which the projection velocity must lie, even when the angle of projection is unknown. In order to facilitate the use of this approach, data have been obtained on the frictional coefficients.

This information is compared with existing field data on pedestrian trajectories. It is found that these pedestrian trajectories correspond to only a percentage of the full velocity of the vehicle. This percentage is large for children struck by vehicles with high front ends, approaching 100%,but is significantly less for adults and for vehicles with low fronts.