How do I determine the speed a car was going by the length of the skid marks?

Question

How do I determine the speed a car was going by the length of the skid marks?

Answer 1

This link should have all the info you need (note: it's a pdf file)

http://www.harristechnical.com/articles/...

Answer 2

Years have gone by since police used skid marks to determine speed.  Disk brakes completely changed the formula where different camps use different scenarios, and ABS have made calculations impossible.

Answer 3

Although the speed of a vehicle can be determined by the length of it's skid marks, the grade of the road and the condition of the tires must also be considered. Also, if the vehicle was still moving at the time of the impact, skid/speed formulas will only yield the minimum "original" speed.

Formula:

Speed = √(30 x CD x Length)