James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::
I’m a collision reconstruction engineer with over 23 years of experience in the field. I’m affectionately known in the office as Captain Video, given my love for the evaluation of vehicle speed and crash-related parameters from surveillance videos.
Basic evaluation from stationary camera:
A 2019 Toyota Sienna minivan passes in front of a stopped dash cam. Speed from video is evaluated therefrom. Speed is distance over time. The easiest way to perform the evaluation is to look at the timeframe required to travel the vehicle’s wheelbase (i.e. the distance from the front wheel or axle to the rear wheel or axle). So, in this example, the minivan travels its 119 inch wheelbase in 7 frames of a 30 frame-per-second video. Distance is 119 inches, or 9.92 feet. Time is 7 frames divided by 30 frames per second, or 0.233 seconds. Calculating speed … 9.92 feet divided by 0.233 seconds is 42.5 feet per second, or ~29 mph. FYI, this was a 35mph speed limit roadway.
Steven M. Schorr, PE, President of DJS Associates, and Laurence Penn, 3D Animations/Technical Assistant ::::
A collision occurred when a northbound pedestrian was crossing a city street and was struck by a right turning, southbound to westbound truck. The truck operator testified that the pedestrian was not visible to him as he executed the turn.
Two surveillance videos picked up portions of the movements of the vehicles prior to and at the time of the collision. A northbound facing camera showed the back of the pedestrian approaching and entering the roadway and showed the front of the left turning truck strike the pedestrian. A southbound facing camera showed the back of the left turning truck and portions of the front of the pedestrian approaching the collision area. The question that needed to be answered was, “could/should the truck driver have seen the pedestrian prior to impact?”