The Traffic Accident Reconstruction Origin -ARnews-

Re: Coefficient of Friction survey.

Ed Livesay (elivesay@alltel.net)
Sun, 27 Jul 1997 09:19:38 -0400 (EDT)

Ed:

Like many others in the field, I've done quite a few tests for drag factor.
I can't recall ever getting a value of less than .73 on dry, flat asphalt.
I've come to believe that reconists should mention the methods used in their
respective testing procedures. As you well know, some reconists use 5th Wheels,
some use accelerometers, bumper guns, sleds, and then we get to "Mu-Meters,"
pendulum testers, spinning disk testers, etc., etc. I've come to realize that
a .70 value as derived from the use of a "sled" is not quite equivalent to a
value of .70 as derived from a MacInnis 5th wheel and so forth....

I've almost always used a VC-2000 accelerometer started by its internal
acceleration sensor. I've also used a sled over the years but I must confess
that like most others, I've been using the sled incorrectly. My recent research
has corrected my sled procedures and I've chosen to use the VC-2000 as its
reference. Now my sled values always quite closely mimic the VC-2000 values.

And so in answer to your question, I would suggest that a value of .70 as
derived by an acceleration sensor initiated VC-2000 would be a good value for
minimal drag factor for typical flat, dry asphalt.
Ed Livesay
elivesay@alltel.net

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