Citation

English J. Accid. Reconstr. J. 2010; 20(5): 23-26.

Copyright

(Copyright © 2010, Accident Reconstruction Journal)

DOI

unavailable

PMID

unavailable

Abstract

Collision investigators must often use a variety of methods to determine the speeds of vehicles involved in accidents. In most cases, there will be physical evidence such as tire marks or gouges, to support a speed calculation. However, in some cases, the physical evidence is inadequate or was not documented sufficiently, so investigators must seek additional evidence. This article reports on the use of video evidence to calculate speed, based primarily on two cases in Hamilton County, Tennessee, where surveillance cameras captured and recorded a collision. The author discusses strategies for applying this methodology and compares it to known data to demonstrate validation of the method's accuracy. In the first Tennessee case, the video from a stationary camera was used to calculate speeds of two motorcycles; the second case involved a camera that was mounted in a moving police vehicle during a pursuit. Two issues must be considered: the distance between the camera and the vehicle and measured objects are located, and the speed at which the video was recorded and played back. The author concludes that even with some small uncertainties about objects location and estimates of the distance traveled, the calculated results for both test series using a stationary camera all were within 2mph or less of the radar speed. Thus, the methodology is not sensitive to small distance variations and closely approximates its actual speed. In the series with the camera mounted in the moving vehicle, the calculated results were also within 2mph of the radar speeds; however, caution must be used to ensure that the camera angle allows a view to be able to compare a known stationary object on the vehicle to passing objects.