PDA

View Full Version : If a skidmark is 15 ft long how fast you think the vehicle was going


sjb6973
Jan 11, 2010, 08:25 AM
Traffic accidents with skid marks

Stratmando
Jan 11, 2010, 08:52 AM
Was the road wet, the tires bald?

sjb6973
Jan 11, 2010, 08:54 AM
The road was dry but covered with salt almost like gravel

sjb6973
Jan 11, 2010, 08:57 AM
Was the road wet, the tires bald?

The road was dry but covered with salt. Almost like gravel

ebaines
Jan 11, 2010, 09:01 AM
I can't speak to iTs accuracy, but the method outlineD in the following PDF file would suggest the car was going about 15 MPH:

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

This assumes that all 4 wheels locked for the 15 ft. and that the "drag factor" for the road surFace is 0.5 (at the low end for asphalt, but could account for the loose salt on the road).

You don't say whether the car stopped skidding because it came to a stop on its own, or did it hit something? If the latter, then obviously the car was going faster than the calculation indicates.

Fr_Chuck
Jan 11, 2010, 09:28 AM
The grade of the pavement, if it was asphalt or concrete all makes a difference in accident investigations,

Here is a calculator to figure speed from skid marks

Accident reconstruction speed calculator (http://harlan-mcgee.com/speed-calc.htm)

But basicy the car was doing between 16 to 19 MPH

sjb6973
Jan 11, 2010, 09:31 AM
I can't speak to is accuracy, but the methoid outlines in the following PDF file would suggest the car was going about 15 MPH:

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

This assumes that all 4 wheels locked for the 15 ft. and that the "drag factor" for the road surace is 0.5 (at the low end for asphalt, but could account for the loose salt on the road).

You don't say whether the car stopped skidding becaiuse it came to a stop on its own, or did it hit something? If the latter, then obviously the car was going faster than the calculation indicates.

The car came to a stop on its own

Fr_Chuck
Jan 11, 2010, 09:37 AM
Then yes the estimates are sound.

Is there a basic reason for the question