ABSTRACT
A time-distance study is the determination of the times at which one or more objects are positioned at one or more locations or times at which various events occur. A time-distance study is often not a part of the reconstructionist’s assignment, but when such a study is requested, there is usually a question to be answered. Examples include:
The driver of which vehicle had the last opportunity to avoid the crash? What are the effects of earlier action (often accident avoidance) by the
driver? What if the driver had been going the speed limit instead of the recon-
structed speed? Once the hazard came into view, did the driver have time to avoid the
crash? Which of the conflicting testimonies is in accordance with the
reconstruction? Could the vehicle actually accelerate fast enough to reach the recon-
structed speed from a standing stop? At what time did a line of sight exist between the vehicles? (Note that
the question was NOT when the drivers could see each other. The reconstructionist is well advised to stay away from such questions as what a person saw, what they thought, etc.)
Each object in a time-distance study has its own time line, and the study is often based on event, such as a collision, that ties the time lines together. The time-distance study may examine the reasonableness of various assumptions that are being made. (E.g., if the vehicles are going at speed 1 and speed 2, they must be a certain distance apart at T seconds before impact. Would there be a line of sight available at that time, consistent with what one witness said?)
Or a more complicated question could be asked. Given that there was a collision, the cars could be backed up along their trajectories to a certain time T before impact. Then the parameters of the motion could be changed, and the clock started in the forward direction again. Would the collision still happen? Would it be at a lower speed? Would the accident mode change? Would the bullet car become the target car, and vice versa? Would the vehicles “whiff” altogether?
