Does anyone know of a website with a formula or calculator that can be used to determine speed from length of skid marks? I was in an accident traveling 45 mph when a truck pulled out in front of me and I hit him. I had no time to stop. The car is a 1989 Ford Mustang GT Convertible, loaded with 4 people including myself, no anti-lock brakes. The extra weight will obviously play a role in stopping distance. I have stock brakes (front rotors, rear drums), and there was approximately 8 miles of street driving prior to the accident (brake fade). The other party claims I was speeding because there are skid marks but I wasn't cited by the police officer. Is there a formula I can use to find out for myself how long it should have taken me to stop? I know the police use one...
I need help! ASAP! Cops welcome...
- Thread starter OUT FOX EM
- Start date
NiteMareGT
New Member
OUT FOX EM said:
If you weren't cited, I wouldn't worry about it. Did they get cited for failing to yield right of way or anything else?
99SilverGT
Founding Member
There are SO many variables involved I can't believe any formula would be even remotely accurate.
SROBERTLAW2003
Member
Yes There Is A Formula In Figuring It Out U Should Have Meassured The Skid Marks From Start To Fadded Finish, Then Weight Of Vehicle Without Ur Peeps Inside And Then There Body Weight. As Well As Road Conditions. Mostly Only Troopers Meassure Skid Patterns For Estimated Speed. Unless U Had Like A 20 Or So Foot Skid Pattern The Policeman Probably Didnt See A Need For The Bother. He Failed To Yield Right Of Way And Its His Fault In My Book And Im A Cop. Based On Info U Listed.length Of Skid Marks Is Most Important When Firguring Your Speed So Im Not Even Goin To Try To Estimate It If U Email Me With Your Guess On Skid Length Ill Formulate It For U Off The Record Lol.
menasci
Member
OUT FOX EM said:
If the other driver was cited and you weren't then you win!
His insurance company is not even gonna waste their time fighting you since he got the ticket.
You're in good shape!
I'm no cop, but I've had quite a bit of experience with this.
They ARE fighting it though! That's what's pissing me off man! Now I'm without a car and they made me a bull$hit offer. I refused it so now I guess they don't have to supply a rental any longer. I just wanted to see if I could disprove their little speeding theory so they can shut up and write a check.
03trubluGT
New Member
There is a formula, and I'll try to get it.
But off the top of my head I know you will nee the Coefficient of Drag to make it work.
This is calculated by draggin an object over the road surface and measuring it with some kind of scale. It is an integral part of the formula, so I doubt if you will be accurate without it.
I do know that at 45 mph you are travelling at about 68 feet per second (mph x 1.5).
Matt
But off the top of my head I know you will nee the Coefficient of Drag to make it work.
This is calculated by draggin an object over the road surface and measuring it with some kind of scale. It is an integral part of the formula, so I doubt if you will be accurate without it.
I do know that at 45 mph you are travelling at about 68 feet per second (mph x 1.5).
Matt
MineralgreyGT01
New Member
Hey how about this?
How to use the chart:
1. Determine the speed in mph after the vehicle has stopped sliding. This might be zero, but generally won't be zero. If the vehicle strikes something at the end of the skid, it is still moving and this residual velocity must be allowed for when using the chart.
2. Move out (horizontally ) on a speed line until it hits one of the curves, the lower is for a 0.7 drag factor, the upper is for 0.8. This is the starting point for finding the speed drop associated with a given length of skid marks with a given residual speed after the mark ends.
3. Move out the length of the longest single skid mark, then move up until you hit the curve again to find the original speed.
EXAMPLES:
a. A vehicle leaves 40' of skid marks before coming to rest- the original speed is about 30 mph for both drag factors.
b. A vehicle leaves 60' of skid marks before striking another vehicle, the damage and post impact slide suggest that its speed was 30 mph when it struck the other vehicle.
1. Move out from the 30 mph line until you hit the curve at about 40'.
2. Add the length of the skid mark -60'- go out to the 100' mark and then up until you hit the curve again at about 46-48 mph. This is the original speed of the vehicle.
So say you impacted at 20 mph that would meen you were going roughly 47-50 mph originally depending on which CoD you use. Good Luck !
How to use the chart:
1. Determine the speed in mph after the vehicle has stopped sliding. This might be zero, but generally won't be zero. If the vehicle strikes something at the end of the skid, it is still moving and this residual velocity must be allowed for when using the chart.
2. Move out (horizontally ) on a speed line until it hits one of the curves, the lower is for a 0.7 drag factor, the upper is for 0.8. This is the starting point for finding the speed drop associated with a given length of skid marks with a given residual speed after the mark ends.
3. Move out the length of the longest single skid mark, then move up until you hit the curve again to find the original speed.
EXAMPLES:
a. A vehicle leaves 40' of skid marks before coming to rest- the original speed is about 30 mph for both drag factors.
b. A vehicle leaves 60' of skid marks before striking another vehicle, the damage and post impact slide suggest that its speed was 30 mph when it struck the other vehicle.
1. Move out from the 30 mph line until you hit the curve at about 40'.
2. Add the length of the skid mark -60'- go out to the 100' mark and then up until you hit the curve again at about 46-48 mph. This is the original speed of the vehicle.
So say you impacted at 20 mph that would meen you were going roughly 47-50 mph originally depending on which CoD you use. Good Luck !
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