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The science behind collision reconstruction

OPP reporting an uptick in collisions across the region, while clarifying it’s ‘normal’ over the summer months

You’ve been involved a collision.

What do you do next?

With Ontario Provincial Police reporting an uptick in collisions throughout the month of August, collision reconstructionists have been busy. Local collision investigators say that’s par for the course, as the summer months see more collisions due to traffic volumes.

There are 10 reconstructionists working for Central Region OPP. They are spread across three traffic teams throughout the region and are called out any time of day or night to attend collision scenes.

“I never thought I’d be using physics, math and science at this point in my career,” laughs Const. Marko Harjupanula, who is part of the Central Region Technical Traffic Collision Investigation (TTCI) team in Orillia.

Harjupanula has been a police officer for 20 years and has been working as a technical collision investigator since 2004.

In 2017, he started as a reconstructionist.

“I enjoy my work now more than I ever have,” he says.

There are numerous ways OPP officers collect evidence at a collision scene, starting with a walk-through and progressing to photographing the scene and vehicles. If necessary, the OPP will bring impacted vehicles to a secure location for a full examination with a forensic mechanic.

“We measure the scene and do a scale diagram,” says Harjupanula. “We measure using a total-station (Theodolite) device, similar to what surveyors use, which measures angles, distances and elevations.

“We document vehicle placement, skid marks, fluid and debris, roadway evidence such as street lights, traffic lights... it’s all documented for the scale diagram, which provides a bird’s-eye view,” he adds.

Harjupanula also says the OPP has the capability at crash scenes to download information from data collectors embedded in vehicles using software. This has been a mandatory feature for all vehicles built within the last five years.

“We can get information from that such as vehicle speed, accelerator position, braking and steering angles, for five seconds prior to the collision,” he says.

After evidence is collected, investigators create a report and will consult with detachment commanders on charges.

Harjupanula says the OPP has six months from the date of a collision to file charges, if they deem it necessary.

“We really want to make sure we get everything right before we go to lay the charge,” he says.

If you are involved in a collision, Harjupanula says preservation of life is the first priority.

“We always say, if the fire trucks and ambulances come to the scene and they drive over the evidence – we prefer they don’t, but if they do, that’s their job – we’ll deal with it after that,” he says.

“Once everybody’s taken care of, try not to move anything. Don’t move your car, just make sure people stay out of the scene as much as you can.”

When asked if there’s anything he wishes the public knew about his job, Harjupanula pleads for a little understanding from the general public.

“People get upset when they’re trying to get somewhere and the road is closed for four or five hours and it’s an inconvenience to them. People have to remember that somebody possibly died or their life is going to change forever,” he says. “It’s a minor inconvenience for them to find a detour or to go to a Tim Hortons to have a coffee while we do our job... it’s minor to them, but somebody’s life has been affected so tragically.

“We have to find out what happened, and we have to make sure we get it done right.”

While the OPP officers tend to handle collisions immediately as they happen, if you’re involved in a collision and choose to go to court down the line over civil matters, you may find yourself dealing with a forensic engineer.

Mark Paquette is a collision reconstruction engineer who works for 30 Forensic Engineering in Toronto, which investigates collisions across the province involving automobiles, heavy trucks, motorcycles, pedestrians, cyclists and recreational vehicles, such as ATVs and snowmobiles.

“For collision reconstruction analysis, we rely mostly on physics, such as Newton’s Laws, the principles of conservation of momentum and energy. We also rely on published testing, such as crash tests and vehicle dynamic testing, such as braking and steering capabilities,” says Paquette.

Paquette also works closely with biomechanics, who rely on an understanding of human anatomy to determine how injuries may have occurred.

Since his firm tends to be hired by insurance companies, lawyers for civil and criminal matters, municipalities, government bodies and law enforcement, Paquette says there’s sometimes a misconception that data will be skewed to prove one result or another, but that couldn’t be farther from the truth.

“We are independent, which means that our findings are not contingent on what would be the best outcome for our clients. In a nutshell, we are not ‘hired guns',” says Paquette. “In other words, we don’t start with a finding that might be better for our clients – our findings are the result of the work and it doesn’t matter who is asking.”

The first step of collision reconstruction is collecting data at the site.

This is done by documenting the damage with photographs and often 3-D scans, downloading the black-box data if the vehicle has one, examining the seat-belts and interior, and, if needed, examine the mechanical condition of the vehicle.

At the collision site, they measure the roadway configuration, search for roadway evidence such as tire marks, scrapes, gouges and vehicle debris (such as glass) and look for any visibility obstructions, such as hedges, which may have affected a driver’s ability to see other vehicles.

“If the collision happened at night, we often measure the lighting in the area or perform a scene re-enactment to understand any visibility concerns,” says Paquette.

The second step of the process is analysis of the collision.

“If roadway evidence was obtained, we determine the rest positions as a result of the collision of the vehicles and work our way back from that,” says Paquette.

Specifically, Paquette’s team will determine the impact speeds that would likely result in the vehicles being redirected to their rest positions.

“One comparison would be playing pool: if we know the weights and speeds of the pool balls, their expected trajectories could be estimated. We do the same thing, but with vehicles,” he says.

Another avenue for analysis can be the physical damage or ‘crush’ sustained by the vehicles. Paquette’s team can compute the amount of energy needed for a specific amount of vehicle crush based on crash tests. After the impact speeds are defined, they then determine the pre-impact motions of the vehicles.

“For example, a driver may have steered or braked before the collision,” says Paquette.

The last step for a collision reconstructionist is to determine if the collision was avoidable, which requires an assessment of when the oncoming hazards could be detected and how quickly a driver should have reacted based on typical reaction times.

“I’m most commonly asked to determine the vehicle speeds, the pre-collision motions and any opportunities the drivers might have had to avoid the collision,” says Paquette. “However, there can be other matters of interest, such as whether the occupants were wearing their seat-belts, or if there was a mechanical defect that caused or contributed to the collision.”

In many cases, Paquette’s team is retained several years after a collision when the vehicles are no longer available. For these matters, they rely on police documentation, damage appraisals and, occasionally, media photographs taken at the scene. They also determine the roadway conditions at the time of the collision as the tire-roadway friction is an important variable. They do this by looking at scene photographs, historical weather data and the reported information.

Overall, Paquette agrees with Harjupanula that when you’re involved in a serious collision, your first priority should be the health and well-being of all the people involved; however, there are some things you can do to help collision reconstructionists with their investigation.

“Documentation is key, in particular photographs of the vehicles, and any roadway evidence,” says Paquette.

“However, in the case of serious motor vehicle collisions, I wouldn’t expect most people to think about my job, as there are going to be much more important things to be concerned about.”

Const. Mark Wickson, another member of the OPP TTCI team based in Orillia, received a commendation for his work investigating fatal collisions. In his cubicle at Central Region OPP Headquarters is a framed letter from OPP higher-ups.

One part of it sticks with him as being the reason fatal collision investigation is so important.

“We conduct a comprehensive and detailed investigation, and the complete report provides an explanation of the events which lead up to a fatal collision, and provide a voice for those who could not,” he reads from the letter.


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Jessica Owen

About the Author: Jessica Owen

Jessica Owen brings 12 years of experience to her role as regional reporter for Village Media, primarily covering Collingwood, County of Simcoe and education.
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