Wearing a seatbelt is one of the simplest and most effective safety systems available in an automobile. There are specific types of physical evidence that can help determine if an occupant was wearing their seatbelt or not. An in-person vehicle inspection is usually the most useful determinant.
What could they see? Could they be seen? Visibility obstructions are often a case of geometry: vehicle, scene, and human anatomy. Nighttime or weather-related visibility are also common inquiries: available lighting, colour contrast between subject and background, hazard recognition and change in available perception response times. 3D laser scanning, exemplar testing, and nighttime visibility re-enactments are common tools we use in these cases.
Who was driving? It’s not uncommon for there to be confusion or uncertainty regarding who was behind the wheel in a collision. Eyewitness reports, physical evidence, seatbelt and airbag usage, DNA samples, and exemplar testing can help determine occupant location and remove any ambiguity.
Perception-Response Time (PRT)
Driver’s cannot instantaneously respond to hazards that arise. They have to notice the hazard, identify what kind of hazard it is, decide how to respond and then perform a physical reaction (i.e. braking and/or steering). All of this takes time. An important aspect in many reconstructions is to consider how long the hazard was apparent and consider the driver’s actual or possible response.
Traffic Signal Timing
Traffic signals are controlled by complex algorithms based on set times, time of day, detected vehicle demand or a combination of all three. This information can be important. For instance, if you have a case where a witness says their light turned green at the moment of impact, we can use the signal timing data to determine where the involved drivers were on the cross-streets when their lights turned yellow and red.
This is the first question that is asked but it is not the only one. Speed can be a critical factor and we have a variety of ways to calculate it based on the collision type and the available evidence. A follow-up question is often whether the collision would have been avoided or been less severe if one or both vehicles were traveling slower.