My car just passed its MOT - I'm not impressed.

ABS is there to deal with one or more wheels locking up under braking - essentially it is automated cadence braking that is capable of cadence braking one or more wheels as needed. The net effect is that any wheel that is locked is simply going to slide, and therefore any control or grip that the tyre could offer is completely negated - furthermore, the locked wheel offers nothing to slowing the vehicle down. By keeping the wheel rotating, more control is retained and braking efficiency is considerably more than it would be with a locked wheel.

I suspect the rust/muck that the garage refers to is on the ring which is essentially a toothed ring that spins around with the rotation of the wheel; the ABS sensor basically 'counts' the teeth (electromagnetism at work) and from that count works out if the wheel is rotating as it should be - - if the ABS sensor can't 'see' the ring or all of the teeth on the ring, it will chuck a warning light on and more often than not it will suspend the operation of the ABS system - normal foundation braking effort is not affected, and would still pass a rolling road test.

Traction control looks for variations in rotational speed of the wheels - when traction is lost, one wheel will spin faster than its counterparts; traction control adjusts power distribution (limiting the power delivered or braking individual wheels) to keep things under control.

My current car has a feature which builds on traction control - active trace control - essentially it monitors body roll as well as taking into account steering angles and speed and will adjust power or ever so slightly brake wheels to keep things nice and tidy. Whilst I don't make a habit of chucking my cars around, I have tried chucking it about a bit and it behaves remarkably well for such a tall car.

 

That does seem to very much depend on the car to be fair @pete - - my 2007 VW Passat was like Bambi in the snow with the traction control on, and the only way to get a modicum of control was to turn it off and allow the driver to make the right decisions. My Audi A4 was a bit better, but when the going really got tough, the traction control went off. I haven't had the QQ that long yet, and haven't had any really slippery stuff, but so far it is MUCH better behaved even in extreme wet conditions.

Half the problem of course is me - I learned to drive in an old Landy, and didn't even have ABS until the mid/late 90's, and learned to drive all shapes and sizes of vehicles with and without ABS. In the bad snow of 2010, I was one of the test bods that took double deckers out in the snow to try and get things moving again - sideways through the main street in Twickenham in a double decker is quite interesting......

 

I have to disagree with you @pete - try driving a large vehicle with air brakes in the wet and slam on without ABS, and then try the same in a similar vehicle with ABS, the difference is utterly remarkable.

I had a situation many years ago on a night that was little short of monsoon conditions; I approached a roundabout (Chiswick Roundabout to be exact), albeit a wee bit quick maybe, and the traffic signals changed so I anchored up and even cadence braked - - I might as well not have bothered, as I sailed on through the lights and had no option but to take my foot off the brakes and go back to the loud pedal to give me some grunt to square the blighter up. That was in an old MCW Metrobus (mid to late seventies); the modern motors do not behave anything like the same under the same conditions - they are much more controllable thanks to the ABS.

 

I had a 360 GLT back in the day, and it was the same - nothing quite like a Volvo when it comes to the back end trying to meet the front end

The Ford Sierra was a close second, mind you. I had a Sapphire that twitched its ar*e more than Miley Cyrus - great fun in the ice and snow.