Anti lock brakes come up eight times in the Gibraltar car bank, which makes them one of the most heavily tested single topics on the paper. Every one of those questions turns on the same idea, so understanding it once answers all eight.
What they actually do
A locked wheel is a sliding wheel, and a sliding wheel cannot steer. Anti lock braking senses a wheel about to lock and releases it just enough to keep it turning.
So the benefit is not a shorter stop. The benefit is that you keep steering while braking hard. The paper asks this from several angles and marks the same idea each time:
- They make the tyres less likely to skid
- The vehicle can be steered while you are braking
- They greatly assist with steering control when braking
How to use them
This is where people lose the mark. The correct technique is the opposite of what drivers were taught before anti lock brakes existed.
Press the pedal rapidly and firmly, and do not let go. The paper marks that twice, once as "rapidly and firmly" and once as "brake rapidly and firmly without releasing the brake pedal". Do not pump the pedal. The system is already doing that, far faster than you can.
The system only engages once maximum brake pressure has been applied, and it helps most when braking in an emergency. In ordinary driving you will never feel it.
When they will not save you
The paper is careful to say they are not magic, and this is the question people get wrong most in this group. Anti lock brakes may fail to prevent a skid on surface water and on loose road surfaces.
The reason is simple. The system works by managing the grip a tyre has. On standing water or on gravel the tyre has almost nothing to hold on to in the first place, so there is little for the system to manage.
Note what is not on that list. Fog and darkness make no difference at all to braking. They affect what you can see, not what your tyres can do. Dry tarmac is where the system works best.
The one line summary
Anti lock brakes let you steer while braking hard. Press firmly and hold. They do not shorten your stopping distance, and they will not help on water or gravel.