St. Stan’s students get crash course in accident reconstruction / iBerkshires.com

ADAMS, Mass. — State Troopers Kyle Cahoon and Sean Curley, members of the Collision Analysis and Reconstruction Section (CARS) Unit, met with students at St. Stanislaus Kostka Middle School to provide an in-depth look at the process and science behind accident reconstruction.

On Friday, May 17, police officers showed students how they determine the causes of car crashes and who might be at fault. Curley said CARS is not called to every crash, only the worst ones that result in serious injuries, deaths or significant property damage.

“If we have a really bad accident where it’s likely that someone won’t survive, then we get a call,” he said. “The trooper on the road then realizes that this is a very, very serious accident and that it may not be within his jurisdiction. He then calls the state police.”

He added that there are four CARS units across the state, but their unit covers the greatest distance in Western Massachusetts – from Worcester to Berkshire County.

“So the response times for us are very long,” he said. “I drove for almost two hours with the lights and siren on.”

According to Cahoon, there are three common factors that contribute to an accident: the driver, the vehicle and the environment. He stressed that accidents are rarely caused by vehicles alone. Instead, human factors such as driver distraction or adverse road conditions are usually the main causes of accidents.

“It’s usually not just an accident,” Cahoon said. “Maybe they were speeding and not paying attention, maybe they were on their cell phone when they shouldn’t be. 99 percent of the accidents we investigate are not accidents.”

In certain situations, Curley said, the vehicle could be to blame. They investigate recalls specifically for the vehicles involved in the accident. If they discover an inherent problem with the make and model of a car, they report it.

“We make sure the mechanics of the vehicle are working properly. It’s not always the main factor, it’s actually a very, very small percentage that the vehicle caused the accident,” he said. “We’ve seen it, but it’s probably one or two percent of the time. 98 percent of the time it’s human error.”

Cahoon said a car accident goes through several phases. The pre-accident phase represents what happens immediately before the accident, while the on-scene phase represents the actual accident and its aftermath.

“So events that lead to the driver possibly perceiving a danger and then seeing the accident itself,” said Cahoon.

Curley added that every crash has a point of no return

“Vehicles get to a certain point where it doesn’t matter what the driver does, physics takes over… things are going to happen whether you want them to or not,” Curley said. “… That’s the point where you usually say a very unkind word and grip the steering wheel as tightly as you can.”

Cahoon said they then began collecting evidence such as tracks and debris on the roadway.

Curley said they are always looking for the impact area

“Where the impact actually occurred, the energy flows down and leaves a nice big hole in the ground,” he said. “That makes our job easier under certain circumstances,” he said. “There’s a crater in the ground. The energy has to go somewhere, so it goes into the two vehicles. Those two vehicles are pushing down, and the ground is what actually stops the vehicles.”

They also look for contact damage – that is, the places where the vehicles touch for the first time.

“That’s where the vehicles actually touch. What happens beyond that is what we call induced damage,” Curley said. “So if anyone has ever seen someone play the accordion or something like that, it’s going to get squashed and come back. That’s the induced damage that wasn’t actually caused by the two vehicles touching.”

Cahoon said that occupants in the vehicle itself are often moving at high speeds and will maintain that high speed even when the vehicle stops.

“Your body wants to keep moving in that direction, so you get the second impact,” Cahoon said. “People in the vehicle with something in the vehicle, maybe a seatbelt or the steering wheel. In the third impact, even your organs still want to move in that direction. So your organs collide inside your body.

Curley said that’s why it’s important to wear a seatbelt. While the seatbelt prevents the occupant from being thrown forward, it also slows them down so the airbag has enough time to inflate and cushion the body properly.

“Your body is moving forward too fast, the balloon is not inflated yet, and it’s going to push you back,” he said. “So now your body is experiencing a worse collision than before because you’re going forward and then you’re pushed backward.”

One of the first things they check is whether the occupants were wearing seat belts, he said. They also check the airbag control module to determine the airbags’ actions during the crash. He pointed out that newer vehicles offer even more information about the vehicle’s behavior during the crash due to more advanced computer systems.

Curley said much of this data is being used to make dangerous roads safer.

To further support their point, Officers Cahoon and Curley led the students outside to a mock accident scene they had set up in the school parking lot. Hampshire Towing brought two crashed cars over for the students to examine.

Here, students were actively involved in hands-on activities, analyzing the accident scene to deduce the direction of travel of the vehicles. Students measured chalk-drawn “skid marks” and used a skid sled to measure road surface friction, an essential factor in understanding vehicle dynamics in a crash.

The students then used various mathematical equations to calculate the speeds of the vehicles before the collision, gaining a practical understanding of the concepts discussed previously.

The brake mark was 7.5 meters long and the friction value was 0.83. This means that the vehicle was moving at 39.9 km/h.

“That’s how we were able to figure out how fast the car was going before impact without anyone helping us,” Curley said. “Without witnesses or anything. We just looked at the roadway to see how fast they were going.”

Curley said it’s not as simple as using a tape measure, and these days CARS members use advanced technology to take accurate measurements.

Cahoon pulled out a GPS stick that uses 18 to 40 satellites to take precise measurements. He said it achieves an accuracy of up to a tenth of an inch.

“We measure the entire roadway and get a series of points,” he said. “We then import these measurements into a computer program.”

Curley said another way to take measurements, and this is his personal favorite method, is to use the CARS drone. He said the drone will fly over the accident scene and take hundreds of pictures of its own. From those photos, a 3D image of the accident will be created.

“If you’ve ever played a first-person shooter game, that’s what it looks like,” he said. “It takes you right to the scene of the accident and shows you exactly what it looks like. On top of that, it’s to scale. I can tell you how tall the car is, I can tell you how wide the car is, I can tell you how long the skid marks are, and I can tell you a lot of different things with the measurements we use.”

But not everyone can buy these tools. Curley said the drone costs nearly $6,000 and the GPS stick is just under $30,000.

He noted that the drone was obviously taking great pictures, and after flying around Spring Street for a bit, he had the students pose for an aerial group photo.

Keywords: Forensics, car accident, St. Stans, State Police,