Determining vehicular speed by length of skid marks?

[Spee-Dee]

Somewhere I heard that in accidents the police who are investigating it can determine how fast vehicle 1 was going when it hit vehicle 2. Anyone know how I can do this? Is there like some sort of mathematical formula?

[pkagel]

http://www.harristechnical.com/articles/skidmarks.pdf
http://www.harristechnical.com/skid33.htm

[PTI]

You can determine the minimum speed the vehicle was traveling. Do a "google" search of "speed from skid formula" and it will give you several sites that explain how to use the formula.

[Spee-Dee]

Ok, thanks. Do you know if these forumlas are used to determine the skid marks of the moving car, or the skid marks of the stationary car that is moved during impact? Basically I'm trying to determine how fast the other car was going to move a stopped car two meters.

Why do insurance forms ask how fast the other car was going anyways? It's not like I can tap into their speedometer and I don't have a radar unit in my car. Yes, if I plan I head I can determine the car's speed in front of me, but I can't figure it out when I don't even know that they're going to hit me.

[PTI]

These formulas are used to determine the minimum pre-impact speed of a moving vehicle. There are many variables to take into account when determining post-impact speed. Most patrol officers don't have the expertise and training to make these determinations. These types of investigations are performed by officers who have advanced training in accident reconstruction. As for why insurance companies ask certain questions you would have to ask someone there.

[Spee-Dee]

These formulas are used to determine the minimum pre-impact speed of a moving vehicle. There are many variables to take into account when determining post-impact speed. Most patrol officers don't have the expertise and training to make these determinations. These types of investigations are performed by officers who have advanced training in accident reconstruction. As for why insurance companies ask certain questions you would have to ask someone there.

They always tell me the same thing. "To help determine the seriousness of the injuries you may have sustained." It was a rhetorical question out of sheer frustration of form-filling out. They're all the same forms that go to different places.

[mobrien316]

The length of the skids prior to collision will only give you a minimum speed. The only time you can get an exact speed is if there is a slide to a stop, and if that happens you obviously don't have a collision.

You can use momentum-based equations to figure out the exact speed of both vehicles in a collision, if you have discernbile approach and departure angles and can use the energy-equivilent speed loss formula to determine the post-collision speeds.

You can go here to check out a list of formulas commonly used by accident reconstructionists.

[Spee-Dee]

The length of the skids prior to collision will only give you a minimum speed. The only time you can get an exact speed is if there is a slide to a stop, and if that happens you obviously don't have a collision.

You can use momentum-based equations to figure out the exact speed of both vehicles in a collision, if you have discernbile approach and departure angles and can use the energy-equivilent speed loss formula to determine the post-collision speeds.

You can go here to check out a list of formulas commonly used by accident reconstructionists.

Wow. So much math! I don't know where to start. The only equations of those I recognize are for constant movement.

[m_chevy]

Unless you are a physicist, or have thousands of hours of specific training, forget about it and pay the reconstructionist his $400 an hour. His opinion will weigh more in court than yours. And that's for your insurance company to buy.

[Spee-Dee]

Unless you are a physicist, or have thousands of hours of specific training, forget about it and pay the reconstructionist his $400 an hour. His opinion will weigh more in court than yours. And that's for your insurance company to buy.

I won't be going to court. She hit me from behind so she's automatically at fault. With all this rear-ending and whiplash I keep receiving I think I'm going to switch over to torte insurance when I renew my licence next week and collect on some pain and suffering. I've already missed 1 and a half shifts of work due to being in so much pain. I don't even want to think of what dance is going to be like tomorrow.

[letshearit4blue]

At our explorer academy the instructor from NYSP said there are hundreds of formulas for basically EVERYTHING and he gave us several for the situations like you mentioned.
We then set up a "scenario" by him leaving skid marks from his car and we had to figure out how fast he was going (his computer thing of course had it exactly). By using the information on distances of skids, wheel bases, and some other stuff we were able to find the minimum speed. We were off by 2 mph of the actual, so we did about how well the recruits do.
If you want the formula they gave us send me a PM and I'll dig it up for ya.

But honestly, I would HATE to go into accident reconstruction. Waaay too much math for my comfort.