The Traffic Accident Reconstruction Origin -ARnews-

What do we see when we look at skidmarks?

Bill Wright (bwright@taro.com)
Tue, 13 Feb 1996 07:04:46 -0500 (EST)

Skidmarks can be as plain as the nose on your face. Dark marks, typically on
an asphalt roadway (not to be confused with tire grindings). Many texts
report the source of these marks as bituminous (tar or oil (hydrocarbons))
material in the asphalt that are made apparent as the friction heated tire
passes over the surface of the road. If this is so:

1) Why, though somewhat less common, do skidmarks appear on concrete roads
that contain no bituminous material?

2) Why can't you make a dark spot by placing a hot object on an asphalt road
(I've tried)?

3) Though a skidding tire face clearly generates big forces and higher
temperatures how much heat can be transferred in the relatively short time
the moving hot tire is in contact with a particular spot on the road?

I have talked to many people that insist the material that makes the mark
comes completely from the roadway. It seems to me that the tire must also be
a contributor.

Bill Wright
bwright@taro.com
http://www.taro.com

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