Sorry Dave, you've got this all wrong.
A driver cannot control the brakes on the edge of lock up if 1 or 2 wheels are locked up. The driver may or not know that and if he does, all he can do is release the brakes and start over. That was called "Pumping" and before ABS was effective.
ABS does this much faster and more efficient then the driver ever could, by releasing ONLY the sliding wheel and not any that are rotating at the same speed as each other. That means that with 1 or 2 wheels sliding, the other 2 or 3 are still being braked. The system measures each wheels speed and then adjusts the brakes to equalize them. When working, the effect you feel in the pedal in only on the wheel(s) that locks, the other wheels are NOT released.
As to 4 wheel skids, the ABS thinks the car is parked, as all 4 wheels aren't moving. So, not only does it not work (Brakes are locked) but you have no steerage, as a locked wheel cannot steer.
The two big problems with ABS is that when working, it starts kicking back in the pedal, the startled/panicked driver lets off the pedal and thus ruins the effect of the ABS.
And they also panic in a slide and DON"T let off (once the wheels are locked) to get the car turning where it needs to go. A rotating wheel can steer, at least a little. ABS cannot work on ice if all 4 wheels lock up instantly, here pumping works better.
With Traction control, the same things apply, With a stick shift, NO driver can control the wheel spin as good as the system can. I was an Acura Tech and handled all the NSX's we sold. Several were raced and it took a lot to convince them that they should leave the system on when drag-racing. Once they did, they found the times were noticeably faster and the tires lasted much longer.
The technology has advanced well past the drivers ability to understand, as most just get in and point and go. They have little or no training, as we older guys did at our fathers side for years, watching him and learning.
Ray
On Feb 12, 2010, at 12:12 AM, Dave Homstad wrote:
Experiments have show that in the hands of an experienced driver, the car can be slowed faster with non-ABS brakes than with ABS. The driver needs to control the brakes at the edge of lockup. The reason is that ABS temporarily turns off the brake on any wheel that locks up, thus reducing braking. Unfortunately, the vast majority of drivers are not experienced or practiced for 4 wheel skids, and panic in a skid, so they benefit from AB
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