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Actually, tests show that if you are braking in a straight line on snow, for maximum braking efficiency (shortest stopping time) it is better to lock your tires because of the pile up effect. Think about what happens in snow (and gravel/sand). When you lock up the tires, you create a little pile of material in the front of your tires that slows you down. When you have ABS, that does not happen.
ABS was never intended to reduce stopping distance on any surfaces. Its primary purpose was to prevent your wheels from locking up thus allowing you to retain control of your vehicle as opposed to plowing straight into something.
If your ABS is going off in the snow, what you should do is start braking MUCH sooner. And whatever you do, do NOT pump your brakes if ABS goes off.
I did a lot of research into this a while ago when a friend and I were having a friendly arugment over the effectiveness and purpose of ABS. He insisted that ABS reduced stopping distance on all surfaces other than snow/gravel/sand, whereas I insisted that that is clearly NOT the case if the driver is able to not cause the brakes to lock up.
We never reached an agreement.
So to recap, in MY opinion:
1) If your ABS turns on and you are about to collide with an object, do NOT release your brakes. Instead, keep your foot firmly on the pedal and STEER AWAY FROM THE OBJECT IF POSSIBLE.
2) If your ABS turns on and you are NOT about to collide with an object, only then release your brakes to allow your tires to return to spinning at normal travel speed and then reapply the brakes SLOWER to prevent ABS from kicking in. This is why it is important to give yourself PLENTY of room when braking on ANY slippery surface. Remember, you do NOT want your ABS going off at ALL if at all possible. ABS is there JUST IN CASE.
3) ABS increases stopping distance on all surfaces when compared to braking maximum braking force without wheel lock. In other words, if you are braking on a surface like wet asphalt or ice and you have no ABS and your wheels lock up, then yes, ABS would have given you a shorter braking distance. BUT if your wheels do NOT lock up and you are really applying the brakes properly, then ABS does NOT give you a shorter distance.
(3) was where my friend and I were in disagreement, and I'm almost positive some here will disagree with me as well. Empirical and unbiased studies with cold hard facts about this are hard to locate, online at least. I Googled for several days attempting to locate information. It seems a lot of the sites would have you believe that ABS is always better, but it seems most of them are just fed the same line from places without any scientific research to back it up. The National Highway Traffic Safety Administration did a few tests. But the problem with these tests is that what they have found is that ABS (no wheel lockup) has a shorter stopping distance than non-ABS (wheel lockup), which any one would agree with, including yours truly, unless they were an idiot.
It seems no one wants to do a test of ABS (no wheel lockup) vs non-ABS (no wheel lockup) and the one place that I did find that managed to do a test a while back had findings that agreed with my point (3).
So if anyone has anything to toss in with this, be my guest. :-)
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'
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