Tire Marks Tell A Story


Matt Van Camp (third from left) instructs Kenneth Serna, Dennie Curtis and Richard Neilsen on how to measure skid marks to determine how fast a vehicle was moving.

Matt Van Camp (third from left) instructs Kenneth Serna, Dennie Curtis and Richard Neilsen on how to measure skid marks to determine how fast a vehicle was moving. Photo by Andy Towle. |

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On the parking lot pavement, two ribbons of black silently sat waiting to tell their story.

Officer Matt Van Camp of the Payson Police Department (PPD) and a former school board member looked down at the skid marks left from his cruiser, then turned to the Payson High School Algebra II class and said, “Go ahead and take your measuring devices and measure from where you see these marks start to where they end. Then we will take these measurements back to your class and I will show you a formula police use to decide how fast the driver was going.”

Van Camp said accident researchers use the formula to determine who was at fault in an accident.

In Rim Country, both the PPD and the Department of Public Safety (DPS) can analyze skid marks from an accident.

He said he has done extra training and does much of the traffic accident analysis for the Payson Police Department. If the crash has fatalities, Van Camp said DPS gets involved.

“DPS does vehicle crimes every day and has expensive equipment to analyze the skid marks,” said Van Camp.

The students, who ranged from sophomores to seniors, plunked down measuring tapes attached to a wheel. They took stock of the marks and did their best to decide the start and stop point.

“Sometimes it’s not easy to do, like when it’s raining,” said Van Camp when the students asked him to help.

Sometimes the start of the skid blends with the black of the asphalt, making the starting and end points difficult to see.

“Just do your best to figure that out,” he said to the students as they bent over to carefully examine exactly where Van Camp’s cruiser has started to skid and ended the skid.

Then he added a twist. He explained that cars without anti-lock brakes leave smooth skid marks and a car with anti-lock brakes leaves dashed marks.

“Look carefully to see the difference,” he told the students.

Van Camp had created both types of skid marks for the students to measure.

The students swarmed over the sets of skid marks, taking measurements and writing down their findings. When they finished, they clutched pieces of paper with their measurements written down and trouped back to Pamela Ryan’s classroom.

“Now the fun begins,” said Van Camp passing out the formulas to the class. “Well, actually the real fun was making the skid marks.”

The kids laughed.

The first formula had friction equaling the speed squared over 30 times the distance.

He told the students the friction amount refers to the state of the road and how the tires reacted to it.

“Today we’ll use point seven,” he said. “If there was rain on the road, we would use point two; if snow, point three.”

He told the class these factors are used universally in skid mark analysis.

“Now get in your groups, use the measurements you took, and figure out how fast I was going,” he said.

The students plugged in the numbers and soon came up with answers.

“You were going 31 miles per hour,” said one.

“60 miles per hour,” said another.

“Holy cow! How do you think I did that in the parking lot?” said Van Camp. “Actually, I was going 38 to 40 miles per hour.”

He said the students could get slightly different speed results because their measurements were probably different.

“That’s where the art of traffic comes in — determining where the skid marks started and stopped,” he said.

If a skid mark will be entered as evidence in a trial, Van Camp said insurance companies hire specialists that get paid more than $380 per hour.

“I sat there just like you guys and thought, when will I ever use this math?” said Van Camp to the students when he could tell they were frustrated.

Now, he said he uses it all the time.

When the students asked him what was the worst accident he had been called to, he told the story of one of his first accidents in the 1990s.

Van Camp said a drunken motorcyclist pulled out of a bar in Star Valley. He decided to impress his friends by driving fast and popping a wheelie, then doing a U-turn to repeat the trick.

Problem was, when he went to repeat the show, a pickup truck had pulled out to make a left hand turn. The motorcyclist did not see the truck, slammed into it and flew off the road into the ditch.

When Van Camp arrived on the scene, he did not see the motorcycle and wondered what all the fuss was, until he looked in the ditch.

“Not a pretty sight,” he said.

Then he pulled out his measuring equipment, pencil and paper and got to work using the same formulas he had just taught the class.

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