Stopping Dead

Whoever taught us to drive was usually concerned with self-preservation, so the first thing most of us ever learned about driving was “...the brake stops the car... yes, the middle pedal... brake... Brake... BRAKE!!!...”. Within our first two or three kilometres of driving we learned braking as the default response to almost any out-of-the-ordinary situation. Steering ran a close second. When, later in our driving careers, a child ran across the street in front of us, our response was instinctive. (“The brake stops the car.”) Another thing we learned about the brake pedal is that the harder we pushed it, the faster we stopped, so, faced with an extreme emergency, we instinctively jammed on the brakes as hard as we possibly could. 

The inevitable result in the era before ABS brakes was that the front wheels locked up in clouds of smoke under maximum braking and it became immediately clear we weren't going to stop in time. Time for Plan B, the heroic swerve around the child. (“The steering wheel turns the car.”) Problem: a car with front wheels locked under braking doesn't respond to the steering, as anyone who's been on a skidpan training session will know. So, just as we jammed on the brakes as hard as possible to 'make' the car stop, we then tried to 'make' the car swerve by turning the steering further and further, sometimes even to full lock. All to no avail. In the era before ABS it was commonplace for drivers to 'freeze' on the brakes, then turn the steering in desperation and finally smash straight into whatever was in their way, shocked to the core by the discovery that everything they believed to be true about a vehicle's two most important controls – the brakes and the steering – was utterly false in extremis. The brake didn't stop the car and the steering didn't turn it!

Since training in special braking techniques to overcome this problem was only available to a small minority of drivers, the question for the engineers was this:  what if it were possible to build a car in which the wheels never locked up, even under the hardest braking, so drivers would always be able to steer round an obstacle they couldn't stop for? Anti-lock brakes (ABS – from the German Antiblockiersystem) had been used on aeroplanes since the 1950s, but the problem was miniaturising the technology to make it feasible for use on cars. This nut was cracked in the 1970s, and from the early 1980s onwards, ABS became widespread. Nowadays, one has to look long and hard to find vehicles which are not equipped with ABS. 

Despite the benefits of ABS, a few important practicalities have tended to be overlooked. For starters, an ABS-equipped car cannot shorten your straight-line stopping distance – the laws of physics still apply. And just because you have ABS doesn't mean you no longer need to keep a safe following distance; after all, you still need reaction and swerving time so you can take advantage of the benefits ABS offers. Indeed, ABS might cause your stopping distance to be longer at lower speeds or on surfaces where a wedge of material could build up in front of your tyres and assist braking on non-ABS vehicles, like in sand or on snow. (This obviously disregards the issue of steering loss with locked wheels.)

Also, ABS cannot work miracles – if there's no traction, there's no traction, and ABS cannot change that, so don't go charging around on ice or in mud as if ABS will flit to your rescue regardless, because it can't and won't. ABS can also not be “assisted” in any way by the driver - it is an autonomous system and if you try to 'pump' the brakes, you are increasing your stopping distance by preventing the computer from applying maximum braking on your behalf.  

And finally, if you frequently activate the ABS in daily driving (the clue is a juddering sound with a pulsating brake pedal), then you are routinely leaving your braking too late and if you one day come across a patch of road surface contaminated by, say, diesel that you didn't notice, you will have no hope of stopping in time.

ABS has virtually eliminated brake-induced loss of control, but it does need a bit of understanding to get the best out of it. Common sense, fortunately, is the one thing for which there is unlikely to ever be an electronic replacement!
Roadside assist | Tools & guides | Travel | Legal | Sitemap