The first step in the reconstruction of a highway crash is the all-important qualitative analysis effort to determine each vehicle’s movements throughout the accident event without consideration of time, distance, or speed.

This process should begin during the on-scene investigation since a reasonable understanding of the dynamics of the crash event can lead to a search for overlooked scene evidence, can raise questions that need to be addressed in the vehicle inspections, and may lead to the identification of possible highway-related accident causation factors.

A reliable qualitative analysis is, of course, essential for the following quantification of speeds, times, and distances to be of any validity. In many cases the physical evidence is not sufficient to calculate reliable speed or time estimates, but the qualitative reconstruction can still be useful. As examples, determining who crossed the centerline in a head-on crash or determining the vehicle approach directions for an intersection collision are extremely important, but do not require speed estimates.

A useful method for checking the calculated results of a completed quantitative reconstruction is to input the results into a computer simulation program. This will yield a qualitative picture to be compared to the assumed point of impact, the pre-crash and post-crash vehicle motions, and the vehicle final rest positions. A significant deviation from the reconstruction conclusion should require another look at the evidence and the reconstruction assumptions.

A similar cross check is available in those cases where a computer animation is developed for a courtroom presentation. If it appears reasonable, it may or may not be a valid representation of the accident event, but if it does not look right, it probably is not right.

In many cases a quantitative analysis cannot be achieved, and in some cases only a partial qualitative analysis is possible. When questioned regarding these missing conclusions a reasonable and easily defended answer is, “I don’t know.”

More information on related topics can be found in Highway Accidents: Investigation, Reconstruction and Causation available at: Information about the book and author is available at: