Effect of ABS on stopping distances (was Re: ABS ACTIVATING @ 3MPH)

[Chris Newbold <cnewbold@transarc.com>]

There was an article in Road & Track, I believe it was July 1997,
in which they tested the effects of ABS on stopping distances under
various conditions.

The car used in the test was a 600-series Mercedes, which they rigged
to allow the ABS to be turned off; they used the stock tires (Michelin
mumble, mumble Energy).

They tested on a number of surfaces using four different methods: 

	1) ABS on, stomp the pedal and hold it until stopped
	2) ABS on, full breaking but driver modulation
	3) ABS off, stomp the pedal and lock 'em up until stopped
	4) ABS off, full braking but with driver modulation
	   (wheels locked, though?!?!)

On all surfaces, entry speed was 30 MPH, except dry pavement where the
speed was 60 MPH; distances are in feet.

I make *NO* claim that I have remembers these numbers correctly. I
am fairly certain, however, that I have approximated the difference
between ABS and no ABS...

	Method ->	1	2	3	4

	Surface
	-----------	
	ice		220	220	150	170
	packed snow	170	180	195	195
	loose snow	180	190	150	150
	fresh snow	180	190	150	150
	gravel		90	70	52	52
	sand		49	50	50	50
	wet		35	50	90	70
	dry		120	140	200+	200+

The testers also mentioned that they didn't really believe in the
"wedge" effect on loose surfaces. While "wedges" of the surface
material did build up, they were not convinced that (smallish)
wedges of snow, etc. could have any significant retarding effect on a
2-ton Benz.

As always, YMMV.

-Chris
1993 90CS