Crash Types
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Crash Types


Crashes at intersections can involve an on-coming vehicle versus a left-turning vehicle, cross traffic and, on rare occasions, two vehicles turning in the same direction where one strays out of their lane.

Single Vehicle Accident (SVA)

Single vehicle collisions often focus on why the vehicle left the roadway. Was it excessive speed, was the driver distracted, did they fall asleep, or was there a mechanical or tire failure that caused the loss of control? All of these are possibilites. The scene evidence and vehicle can often be enough to answer these questions.

Pedestrians and Bicycles

Pedestrian and bicycle accidents often result in severe injuries and involve what may seem like minor details. GPS bike computers, fitness apps on smart phones, and scene/vehicle evidence can often tell us all kinds of information: How fast was the pedestrian traveling? For how long and how far were they visible to the driver? Did they cross in the crosswalk? How fast was the vehicle going?


Motorcycle and scooter accidents present unique challenges that require specific methods to calculate speed and other collision details. The ability of the rider has a much larger affect on the dynamics of a two-wheeled vehicle, which often results in a loss of control. Braking, cornering, speed, visibilty, and avoidability are common variables that can be solved to deduce a cause.

Low Velocity Impact (LVI)

A low velocity impact is typically one with an impact speed below about 20 km/h (but there is no set definition). In these collisions the main question is often, how severe was the collision? That can be addressed by examining the damage, or by the event data recorder, or occassionaly by other methods. Other questions can be which vehicle was moving or who changed lanes into whom?

Commercial Vehicles

Heavy trucks, city buses and highway coaches present unique issues. They are equipped with complex air brakes, engine braking and other systems that can affect vehicle dynamics. These vehicles often have event data recorders built into the engine control computer and may have other on-baord recorders. We have analyzed many such cases to determine speed, stopping ability, roll over from weight shift, etc.

Common Issues

Seatbelt Use

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 visibilty re-enactments are common tools we use in these cases.

Driver ID

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 useage, 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 travelling slower.