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

The Traffic Accident Reconstruction Origin -ARnews-

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

Ed Phillips (edphill@aol.com)
Thu, 5 Dec 1996 13:32:20 -0500 (EST)

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John - Asphalt road surfaces are a combination of road-oil mixtures (typically AR 4000 or similar) combined with gravel and sand. Concrete as well as asphalt heats up and expands on hot days (expansion joints are installed for this purpose). I work for a major metropolitan and urban traffic engineering department. One of the on-going experiments we do is to dynamically test road surface mixtures from sand to asphalt to chip-seal to concrete to dirt. We use various vehicles and braking systems, and we test surfaces that have been layed under various temperature applications for the mixture and ambient conditions and are a variety of ages. When we are finished testing, whether the surface is asphalt or concrete the tires are squared off . This is not true of sand surfaces or dirt surfaces. There may occasionally be some asphalt material adhered to the tire, but the tire is the worse for the wear. The gravel and sand work in the asphalt mixture to erode the tire (whether it is r
olling down the road surface or being dragged across the road surface). The cured mixture rarely shows any evidence of being melted or tacky to the touch. Certainly not along the length of the tire mark. I have seen asphalt surfaces scorched by intense heat from vehicle fires. There is no resemblence to what I view along the path of the tire mark immediately after it has been deposited and those surfaces that are scorched. I hope this helps some.

Ed
Ed Phillips
edphill@aol.com

Next message: John E.Luerding: "Seatbelts not workin in Corovetts."
Previous message: John E. Luerding: "Re: What do we see when we look at skidmarks?"
Maybe in reply to: Bill Wright: "What do we see when we look at skidmarks?"
Next in thread: Bob Lighthall: "Re: What do we see when we look at skidmarks?"

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