I Was In A Wreck

[Future_TX_Cop]

Last Sunday evening (7-11-04) I was involved in a wreck and I was just curious as to how the DPS determined from my skid marks that I wasn't speeding. I know that I was going right at the speed limit (60 mph) when I got around the curve and noticed the Land Rover sitting in the middle of the road. What type of system is used to determine a vehicles speed from skid marks? I know that I wasn't speeding and I am very thankful that whatever system was used proved that because the other driver said she was partly at fault but she knew I was speeding so I too was at fault. She was issued a ticket for failure to yield the right of way and I wasn't issued a ticket. Thanks in advance.

[darrell]

road conditions, tire compound, legenth of skidmarks, size and weight of vehicle. Calc/Trig and other math tossed in with some formulas will give them the approx speed. Unless your speed odometer was stuck at the speed you made contact with.

[michiganstud]

Last Sunday evening (7-11-04) I was involved in a wreck and I was just curious as to how the DPS determined from my skid marks that I wasn't speeding. I know that I was going right at the speed limit (60 mph) when I got around the curve and noticed the Land Rover sitting in the middle of the road. What type of system is used to determine a vehicles speed from skid marks? I know that I wasn't speeding and I am very thankful that whatever system was used proved that because the other driver said she was partly at fault but she knew I was speeding so I too was at fault. She was issued a ticket for failure to yield the right of way and I wasn't issued a ticket. Thanks in advance.

Its very complicated to explain, but I can tell you that we can figure your speed down to almost 1 or 2 miles per hour.

You take the length of the skid mark, drag factor and a few other things/variables and put them all into a formula. If you want the exact formula I can put it here.

[darrell]

I forgot drag factor. I have my formula cheat sheet someplace...... If I could only find it.

[Whitewolf1970]

I forgot drag factor. I have my formula cheat sheet someplace...... If I could only find it.

cheat sheet? Nope, I have it in my desk, you will wait until the end of the class, Darrell.

[michiganstud]

LOL....awsome

But actually the newest thing lately is taking the computer out of the vehicle. The computer will hold a certain amount of information before a crash, and yes, the speed is one of them. They can also tell if you were braking, etc.

[Whitewolf1970]

I remembered the time Bratton got angry, he doesn't allowed any cheat and lazy technologies in his PD. So he turned everything back to the old fashioned ways. Did officers like it, nope, they groaned...so they have to guess it and DO math!

[sgtbear111]

Speed is computed from a slide to stop formula, or more complex math as the variables increase. The variiables are the visible skidmark distance, number of wheels locked, and the coefficient of friction of the road surface (weather & road surface etc). Other variables are driver recognition and driver reaction time, the partly locked wheel marks (impending skidmark) and any velocity at collision point. The speed computed shows the vehicle was gpong at least that speed. Certified collision techs or reconstructionists use these formulas frequently.

[Whitewolf1970]

cool technologies, many PDs still hold 'em except for the LA area...when he first announced it after he became a Chief...Ouch!

[Future_TX_Cop]

Thanks to everyone. I didn't know if it was complex because my insurance adjuster said he had to "measure the skidmarks and then look at a chart" to come up with a speed. He made it sound like he just had to measure the skidmarks and then look at a chart and I knew that couldn't be all because my skidmarks were only probably 6-10 feet long because I couldn't see the Land Rover until I was completely around the curve and the road they came off of it just a few feet after the curve. My truck is totaled but there wasn't any life threatening injuries to any of us. I had two girls with me and one had to be care-a-flighted to a hospital about 50 miles away and the other was treated and released at our local hospital just like I was. The State Trooper who responded to the accident told me that it was a "miralce anyone survived the wreck!" After I hit the Land Rover we slid off the road, bounced off a huge oak tree and then went through a fence.

[michiganstud]

Thanks to everyone. I didn't know if it was complex because my insurance adjuster said he had to "measure the skidmarks and then look at a chart" to come up with a speed. He made it sound like he just had to measure the skidmarks and then look at a chart and I knew that couldn't be all because my skidmarks were only probably 6-10 feet long because I couldn't see the Land Rover until I was completely around the curve and the road they came off of it just a few feet after the curve. My truck is totaled but there wasn't any life threatening injuries to any of us. I had two girls with me and one had to be care-a-flighted to a hospital about 50 miles away and the other was treated and released at our local hospital just like I was. The State Trooper who responded to the accident told me that it was a "miralce anyone survived the wreck!" After I hit the Land Rover we slid off the road, bounced off a huge oak tree and then went through a fence.

All that and only 6 feet of skid!?! :eek:

[Future_TX_Cop]

All that and only 6 feet of skid!?! :eek:

Yes. There was no way for me to see the car in the middle of the road until I was completely around the curve. As soon as I saw them in the middle of the road I slammed on my brakes but we were already right there in her driver-side door. The road the wreck happened on is a "farm road" and it has a lot of spots were you can't see cars that are coming off of side roads until you are right at the side road. There wasn't anything I could do to avoid the wreck because the lady decided to basically stop in the middle of the two lane road blocking both lanes.

[mcsap]

Skids prior to an impact can be used but skids AFTER impact cannot. With a very short skid prior as you describe, it would not be worth my time to even do the math. The only way to determine a MINIMUM speed would be from a crush analysis of your car or the other car which is a time consuming process. We only do it for serious injury or fatal crashes.

Having said that , it certainly does appear that you were doing every bit of the 60mph you described. If you weren't cited, that is a plus.

[sbrad]

If I have to determine speed from a crash, then that means someone either died or is knocking on heaven's door. And if that's the case then I call a traffic accident specialist and HE works the accident. So you'll have to ask him.

[mcsap]

It doesn't matter what speed the other driver accuses you of doing. The evidence at the scene tells a tale and the tale was that you were not cited for any speed violation. That is all that matters.

And I am an Advanced Accident Investigator.