Category : Collision / Accident Reconstruction

Two Collision Contributors, One Code Violator


Robert T. Lynch, PE, Senior Collision Reconstruction Engineer ::::

A motorcycle traveled across the double yellow centerline into the opposite travel lane on a rural, two-lane roadway in order to pass a farm tractor. When the tractor turned left at the intersection a collision occurred. DJS Associates was retained to evaluate the matter to determine the contributing factors that led to the subject incident. The incident would have clearly been avoided if the tractor operator hadn’t turned left or if the motorcyclist decided not to pass the tractor at the intersection. So, in general, the actions of both operators could be considered as contributory. However, a review of the (Pennsylvania) state statutes indicated that the actions of the motorcyclist were in violation of the vehicle code while the tractor operator’s actions were in compliance with the vehicle code

The vehicle code requires that a left-hand turn be completed from the left-most lane available, and that the driver of a vehicle intending to turn left at an intersection yield the right-of-way to any vehicle approaching from the opposite direction which is so close as to constitute a hazard. From an engineering perspective, the actions of the tractor operator to turn left at the intersection from the travel lane were in compliance with the vehicle code.

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What Could the Truck Operator See? The 3D Evaluation of Surveillance Videos

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?”

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Technology that Increases Pedestrian Safety at Night

Robert T. Lynch, PE, Sr. Collision Reconstruction Engineer ::::

On average, a pedestrian is killed every two hours and injured every 7 minutes in traffic crashes in the United States with an overwhelming proportion of fatal collisions occurring at night . When corrected for mileage, nighttime fatality rates in the United States average more than three times greater than daytime rates. Under dark conditions, drivers rely on artificial lighting, such as from street lights and vehicle headlights, to illuminate their path in order to identify potential hazards. Not all roadways have street lights, and with the limitations of most vehicle headlight systems, drivers often “overdrive their headlights” where, at speeds as low as 35 miles per hour, a driver may be faced with an emergency where he or she cannot perceive, react and avoid the impending collision.

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Speed From Video… Another Masterpiece


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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Don’t Underestimate the Importance and Power of Event Data

Event Data

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

The capability of recording event data when a crash occurs is becoming more prevalent in vehicles on the road today.

Once a crash occurs, as part of the investigation process, event data should be collected from all vehicles involved that have such recording capability.

Having been collected, the data can be reviewed and analyzed by a collision reconstruction engineer, as part of his or her analysis process. And yes, you do need to be trained in order to properly interpret, analyze, and incorporate this data into a collision reconstruction.

Oftentimes, the client is interested in knowing such things as how fast a vehicle was traveling, and whether the operator applied the brakes before impact.

Take, for example, a collision involving a Ford Ranger pickup running into the rear of a motor coach. The crash took place pre-dawn, as the motor coach was starting from a stop when the traffic signal turned green.

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3D Animation: Man Struck by Carrier While Opening His Driver Side Door

Hugh Borbidge, Senior Mechanical Engineer ::::

Are you a good judge of distance? Sometimes not being able to estimate how much room you have can lead to disaster.

In the following case, a man simply walked to his double parked truck and opened his driver side door to get in. At the same time a car carrier was traveling down the street towards the man. Did the man have enough room to open his door with a truck passing by? The whole thing was caught on tape but it was hard to tell how much space was available.

DJS was hired to recreate the scene so we could accurately measure what happened. We collected laser scan data, modeled vehicles and pedestrians and recreated the movement and spatial relationships based on the surveillance video. We were able to determine that had the man waited for the truck to pass, he would have been able to safely open his door and get in.

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