St. Stan's Students Get Crash Course in Accident Reconstruction
ADAMS, Mass. — State Troopers Kyle Cahoon and Sean Curley, members of the Collision Analysis and Reconstruction Section (CARS) Unit, met with St. Stanislaus Kostka middle school students to provide an in-depth look into the process and science behind accident reconstruction.
On Friday, May 17, the troopers showed students how they determine the causes of vehicular crashes and identify who may be at fault. Curley said CARS is not called to every accident but only the worst of the worst that conclude in severe injury, death, or considerable property damage.
"If we have a real bad crash where somebody is likely not to make it, that's when we get a phone call," he said. "The officer on the road will realize that this is a very, very serious crash, and it might be outside of his scope of what he does. He'll call the State Police."
He added that there are four CARS units across the state, but theirs covers the largest distance in Western Mass — from Worcester to Berkshire County.
"So, there are response times for us that are a long time," he said. "I have driven for almost two hours with my lights and sirens on."
According to Cahoon, there are three common elements that contribute to a crash: the driver, the vehicle, and the environment. He emphasized that accidents are rarely caused solely by vehicles. Instead, human factors, such as driver distraction or adverse road conditions, are typically the primary causes of accidents.
"It's not typically just an accident," Cahoon said. "Like they might be speeding and not paying attention, they might be on their cell phone when they shouldn't be. Ninety-nine percent of crashes we investigate are not accidents."
In certain situations, Curley acknowledged that the vehicle may be at fault. They investigate recalls specific to the vehicles involved in the accident. Should they uncover an inherent issue with a car's make and model, they report it.
"We'll make sure that the mechanics of the vehicle are working appropriately. It's not always the major contributing factor, it's actually a very very little percentage that the vehicle caused the crash," he said. "We have seen it, but It's probably like one or two percent of the time. 98 percent of the time is human error."
Getting into the actual crash, Cahoon said a car crash has different phases. Pre-scene represents what happens immediately before the crash while on-scene represents the actual crash and the aftermath.
"So events that lead up to the driver's point of possible perception of a hazard and then on seeing the crash itself," Cahoon said.
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 like it or not," Curley said. "…That's when you usually say a very not nice word and you just hold on to the steering wheel as hard as you can."
Cahoon said they then start gathering evidence such as marks and debris on the roadway.
Curley said they always look for the area of impact
"Where the impact actually happened that energy tends to go down, and it'll make a nice big hole in the ground," he said. "So it makes our job easy in certain circumstances," he said. "There's a crater on the ground. The energy needs to go somewhere, so it goes into the two vehicles. Those two vehicles push down, and the ground is actually what stops the vehicles."
They also look for contact damage — or where the vehicles initially touch.
"It is where the vehicles actually touch. What happens outside of that is what we call induced damage," Curley said. "So if anybody's ever seen anybody play the accordion or anything like that, it like squishes together and comes back. That is the induced damage that wasn't actually caused by the two vehicles touching."
Moving inside the actual vehicle, Cahoon said because the occupants are often moving at high speeds, they will continue at that high speed once the vehicle stops.
"Your body wants to stay moving in that direction so there's the second collision," Cahoon said. "People inside the vehicle with anything inside the vehicle, maybe a seat belt or the steering wheel. There's the third collision where even your organs are still wanting to move in that direction too. So there's your organs crashing inside your body
Curley said this is why it is important to wear a seat belt. While the seat belt prevents the occupant from being propelled forward, it also slows them down, giving the airbag enough time to inflate and provide adequate cushioning for the body.
"Your body is moving too forward too fast, the balloon hasn't blown up yet, and what it will do is, it'll push you back," he said. "So now, your body's experiencing a worse crash than what's happening because you're going forward and then being pushed backward."
One of the first things they inspect is whether the occupants were wearing their seat belts, he said. They also pull the airbag control module to determine the actions of the airbags during the collision. 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 used to make dangerous roads safer.
To further illustrate their points, Troopers Cahoon and Curley took the students outside to a mock crash site they had set up in the school parking lot. Hampshire Towing brought over two crashed cars which the students could investigate.
Here, students were actively involved in hands-on activities, analyzing the scene to deduce the directions in which the vehicles were traveling. Students measured chalk-drawn "skid marks" and employed a drag sled to measure road surface friction, an essential factor in understanding vehicle dynamics during a crash.
The students then applied various mathematical equations to calculate the speeds at which the vehicles were moving before the collision, providing them with a practical understanding of the concepts discussed earlier.
The skid mark measured 24.5 feet and the friction value was 0.83. This means the vehicle was moving 24.69 mph.
"That's how we find out how fast the car was going prior to impact without anybody helping us," Curley said. "Without witnesses or anything like that. We just used that roadway to tell us how fast they were going."
Curley said it is not as simple as using a tape measure, and these days CARS members use advanced technology to take exact measurements.
Cahoon pulled out a GPS stick that uses 18 to 40 satellites to provide exact measurements. He said it gives them accuracy of up to one-tenth of an inch.
"We will measure the whole roadway and get a bunch of points," he said. "We then import those measurements into a computer program."
Curley said the other way to get measurements, and his personal favorite, is to use the CARS drone. He said the drone will fly over the scene and take hundreds of pictures on its own. These photos are used to create a 3D image of the crash.
"If you ever played a first-person game it looks like that," he said. "It can bring you right to the crash and show you exactly what it looks like. On top of that it is 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 that we use."
But these aren't tools anyone can purchase. Curley said the drone costs nearly $6,000 and the GPS stick is closer to $30,000.
He noted that the drone obviously takes great pictures and after flying a bit around Spring Street he had the students pose for an aerial group photo.
Tags: forensics, motor vehicle accident, st stans, state police,
