The Traffic Accident Reconstruction Origin -ARnews-

Re: What do we see when we look at skidmarks?

Bill Coltharp (cea@onr.com)
Sat, 17 Feb 1996 19:53:39 -0500 (EST)

I have a theory (only a theory) that skidmarks fall into one of two classifications
1. Those on asphalt surfaces are due to the effect of heat and pressure
on the asphalt. The combination of the two causes oil from the
asphalt to bleed to the surface of the road. It is the same thing
that causes the wheel rut tracks on asphalt roads in warm weather
areas such as Texas.

2. Those on concrete surfaces (and to some extent hard gravel roads) are
due to small particles of rubber from the tire being scraped off of
the tire by the micorscopic roughness of the concrete. These marks
are often more visible when viewed in the direction the vehicle was
going because the rubber tends to accumulate on that side of the
concrete particles.

I think that such marks could be caused on asphalt surfaces using heat if
there was also suitable pressure.
Bill Coltharp
cea@onr.com

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