Hugh Borbidge, BSME, Director of Engineering Animations
Often, drivers involved in a collision will profess that each had their corresponding green light. Unless there is a signal malfunction, both cannot be right. Sometimes there are clues to help determine which vehicle operator was at fault.
In this case, the tractor-trailer driver stated that he had the green left-turn arrow; the oncoming SUV driver stated that he had the green light; and the witness said that they received the green light about five seconds after the accident happened.
Utilizing a signal timing plan, witness testimony, and the laws of physics, we can determine who was at fault. Working backwards, the witness statement puts the collision at five seconds prior to their light turning green. At five seconds prior to the witness light turning green, the tractor-trailer’s light would have been a yellow left-turn arrow. The tractor-trailer’s light would have been a green left-turn arrow for 12 seconds prior to the yellow left-turn arrow. It takes the tractor-trailer about 14 seconds to travel from the stop bar to the point of impact. These facts check out.
The 3D animation shows this signal timing along with the corresponding vehicle movements.
Result: It would not have been possible for the oncoming SUV to have had a green light under this signal timing pattern.
Hugh Borbidge, BSME, Director of Engineering Animations with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.