The Traffic Accident Reconstruction Origin -ARnews-

Re: ABS Brakes

Kent.Autrand, Stockton PD ([email protected])
Wed, 9 Dec 1998 12:28:04 -0500 (EST)

Stockton PD, CA. We have done a number of tests with both Chevy and Ford police units equipped with ABS. We conducted both straight line and hard evasive turn barkaing tests.
At speeds as low as 35-40 MPH, straight line, we observed front tire marks on the Chevys. The Ford Crown Victs did not mark as well as the Chevys.
In hard right turns we observed what appeared to be centrifigual scuffs except both front tires tracked as did the left rear.
Stopping distance during the turning maneuver increased over straight line braking. Measured coefficient of friction was .86 in staight line and .51 to .53 during the turning movement.
The scuffs left during the turn/brake application could easily be mis-interpreted as centrigigual scuffs by an inexperienced investigator.
During high speed, 60+ MPH, brake/turn there was a sense of brake failure. We believe this sensation is due to the decreased coefficient of friction as the available friction is being applied to
both the turning maneuver and stopping. This experience has been widely reported as brake failure by officers involved in hard braking and evasive turns.

Kent Autrand, Stockton PD
[email protected]

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