Tag Archives: James R. Schmidt

Captain Video and the 3 Car Scenario


James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::

By now, you’ve likely seen our speed from video evaluations. It doesn’t matter whether it’s a still camera, a moving camera, a dash cam video, daytime, or nighttime. If we can identify sufficient points of reference, we can evaluate speed of a given vehicle from video.

In this example, we’re evaluating speed of three vehicles from one clip: 1) the vehicle equipped with the dash cam (vehicle 1); 2) the vehicle a distance ahead of vehicle 1 (vehicle 2); 3) a vehicle travelling in the opposite direction (vehicle 3). We are able to assess additional vehicles, if that were necessary.

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Speed from Video – Captain Video’s Specialty


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.

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Collision Reconstruction Tidbits


James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::

A vehicle traveling 50 miles per hour (73.3 feet per second) emergency brakes to a stop on a dry roadway in 119 feet. That same vehicle traveling down a 5% grade, for example, takes longer to stop, as the downgrade effectively reduces the friction. The braking distance for that vehicle would be 128 feet. When traveling uphill the opposite is true, as the uphill grade (again, assuming 5%) effectively increases the friction, resulting in a braking distance of 111 feet. The higher the friction, the quicker a vehicle can stop. The lower the friction, the longer it takes a vehicle to stop.

Speed from video can be an easy thing to evaluate. Of course, we must be able to see the vehicle of interest and the video needs to be of a good quality with a constant/known frame rate. Speed is simply distance divided by time. For example, if a vehicle travels 100 feet in 1.37 seconds, its speed is 73 feet per second (or approximately 50 mph). Alternatively, if the view of the vehicle is limited to something small, or just a “blip”, the time it takes the vehicle to travel its wheelbase (i.e. distance from front axle to rear axle) can be used. For example, a 2007 Honda Odyssey minivan passes through the field of view of a surveillance camera, and in doing so it travels its wheelbase of 118 inches (9.83 feet) in 4 frames of a 30 frame per second video (0.133 seconds). Speed is calculated at 73.8 feet per second (or approximately 50 mph). Each case is unique, and evaluations ranging from simple to complex, using traditional to advanced 3D computer-aided methods, can be performed to determine speed and many other parameters that may be of interest.

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Sunglare … Where?


sun-glare-1

James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::

This is one of the times of year where motorists are regularly encountering sun glare. The sun is low in the eastern sky during morning rush hour. The sun is low in the western sky during evening rush hour.

Take this morning, for example. I was on my ride to work, and voila … sun glare!

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Speed From Video… Another Masterpiece


speed-from-video-

James R. Schmidt, Jr., BSME, Sr., Collision Reconstruction Engineer ::::

As you probably know by now, DJS can analyze dash cam and still-camera surveillance videos to quantify vehicle speed (and other parameters, if necessary). Of course, the ability to evaluate is dependent on the quality of the video, as well as the presence of fixed objects or other points of reference visible in the video for use in determining distance travelled over time (i.e. speed is distance divided by time). DJS has performed this type of analysis countless times. Quite possibly, DJS has worked with you on a case in which such an analysis was performed, or you may have read some of our other prior articles wherein this topic has been discussed at length.

With a video in hand (a dash cam video in this instance):

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Mobile Digital Billboards!


Digital Billboard

James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::

I recently saw my first mobile digital billboard truck while on the road. It was very eye-catching, and somewhat distracting, to say the least. The reflection of the digital display off the wet roadway contributed to the distraction. If you happen to see a mobile digital billboard truck while driving, be sure to keep your eyes on the road as best you can!

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