Expertly Speaking

Dr. Justin P. Schorr on Autonomous Cars with Marc Hoag


Dr. Justin Schorr joins Marc Hoag, Dr. Martin Adler (Netherlands), and Dr. Henning Lategahn (Germany) for the Season 3 Finale of Autonomous Cars with Marc Hoag. Their discussion on nearly every angle surrounding autonomous vehicles ranges in topic from technology to societal impacts, and everything in between.

Listen to the podcast here – https://www.podbean.com/media/share/dir-kdzqx-6299ada

Justin P. Schorr, Ph.D., Principal Collision Reconstruction / Transportation Engineer with DJS Associates, can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

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Virtual Reality Premieres at DJS Associates


Laurence R. Penn, Senior Forensic Animation/Video Specialist ::::

 

On Friday May 3rd, at the Forensic Storage and Technology Center, DJS Associates was proud to host a CLE approved Seminar, “Investigating Vehicular Collisions: An Interactive Seminar Where YOU Take Part in the Investigation” in which we discussed the many old and new ways of collecting physical and digital data for collision reconstruction, and how that data is used for analysis. The final presentation of the seminar demonstrated how a 3D reconstruction can be experienced through Virtual Reality, produced in-house by DJS Associates. With current real-time interactive 3D technologies, one can step into the driver’s seat and view the circumstances at the time of the collision to watch them unfold. The addition of our interactive steering wheel, pedals and hand trackers assisted in making the experience as immersive as possible for attendees.

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Slip and Fall Accident in Walk-in Cooler


Bryan J. Smith, PE, Construction Site Safety/Slip & Fall/OSHA Consultant ::::

Case Description/Summary: While preparing for an annual festival the plaintiff, a temporary employee of the property owner, was helping a frozen fish delivery person load the delivered products into an exterior walk-in cooler. The plaintiff loaded the product boxes onto a cart with intentions to pull the cart to the cooler’s interior metal ramp so that he didn’t have to carry each box individually. He never looked down at the ramp floor before stepping upon it.

The plaintiff’s walking actions were not those of a normal pedestrian walking upon a flat, level surface. He was on a sloped ramp that was 8.3% sloped from the normal plane (a moderately slight incline from a horizontal plane). Under normal walking conditions, this slope would be considered shallow and far from being excessive – even for pedestrians with walking difficulties. The steeper the slope, the more a pedestrian standing on it will have his weight (see black arrow in the illustration below) act to affect a slide down the ramp. As the weight is applied to the sloped surface, a portion of the weight vector will go “normal” (perpendicular – see yellow arrow) to the ramp’s surface. The remaining force vector of the weight would be applied parallel (see green arrow) to the sloped surface.

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Zip Line Trees

Giant Swing Fall


John R. Yannaccone, PE, Senior Mechanical Engineer ::::

Case Synopsis: An employee of an outdoor adventure facility was participating in an in-house training scenario where the employees were to complete a rope course. One of the obstacles involved a giant swing that used a carabiner to connect the participant’s harness to a swing line attached to two trees. A second line was connected to a quick release and was used to pull or haul the participant approximately 25 feet up. The participant pulled a small rope to actuate the release mechanism, which dropped the haul line and allowed the participant to swing from the swing line.

Several other participants had safely used the giant swing on the day of the incident prior to the plaintiff’s turn. When it was his turn, the plaintiff went to the bottom of the swing where the operator (another employee) connected the two lines and the plaintiff was hauled up. When the plaintiff pulled the release rope, he was completely discharged from the swing and fell approximately 25 feet to the ground where he sustained serious injuries.

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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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trucks

Fifth-Wheel Decoupling


R. Scott King, BSME, Principal Automotive / Mechanical Engineer ::::

A commercial semi-trailer detached from its tractor and came to rest within the roadway, blocking several travel lanes. Before the tractor-trailer operator could place her reflective warning devices on the roadway, the operator of an oncoming passenger vehicle approaching the detached trailer steered sharply to avoid it and in doing so, lost control of her vehicle resulting in significant injuries to herself and the occupants within the vehicle. A post-incident investigation revealed the tractor-trailer combination had recently departed its terminal and traveled several miles before detaching. Police investigators concluded that the sole cause of the separation was that the operator failed to properly connect the tractor and trailer before departing for the trip. Forensic engineers, however, came to a more detailed conclusion.

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