Anti-lock braking system (ABS)
A system that stops the wheels locking under heavy braking so you can still steer — not a shorter stopping distance.
Under very hard braking a wheel can stop turning while the car is still moving. A locked wheel has lost the grip it needs to steer with, which is why a heavy-braking emergency without ABS so often ends with the driver sliding straight on. ABS releases and reapplies the brake many times a second to keep the wheel rotating.
What that buys you is steering. You can brake hard and change direction at the same time, which is precisely what an emergency usually requires. The technique is to press firmly and keep pressing — do not pump the pedal, and do not be put off by the shuddering and noise through the pedal, which is the system working.
The common misconception, and a favourite exam question, is that ABS shortens stopping distances. It may on a good surface, but on loose gravel, snow or ice it can lengthen them. It is a steering aid, not a substitute for leaving enough room.
25 practice questions on this
Each one shows the answer, and our note on why every other option is not it.
Car
- What should you do if your anti-lock braking system (ABS) warning light stays on? Safety and your vehicle
- If you're involved in a collision, what will reduce the risk of neck injury? Safety and your vehicle
- On what type of road surface may anti-lock brakes be ineffective? Safety margins
- You're driving a vehicle that has an anti-lock braking system (ABS). How should you apply the footbrake when you need to stop in an emergency? Safety margins
- When would you increase the pressure in your tyres so that it's above the normal value? Vehicle loading
- How should you use anti-lock brakes when you need to stop in an emergency? Safety margins
- You're planning to tow a caravan. What will help the handling of the combination? Vehicle loading
Motorcycle
- You're riding a motorcycle that does not have an anti-lock braking system (ABS). What should you do if you have to brake sharply and your motorcycle starts to skid? Motorcycle handling
- You're riding a motorcycle that does not have an anti-lock braking system (ABS). What should you do if braking too hard has caused both wheels to skid? Motorcycle handling
Lorry & Bus (LGV/PCV)
- What's the principal braking system on a lorry called? Braking systems
- Your lorry is equipped with anti-lock brakes. What's the correct procedure for stopping in an emergency? Braking systems
- How will anti-lock brakes improve your vehicle's safety? Braking systems
- Your vehicle is fitted with an anti-lock braking system. What's it designed to allow you to do? Braking systems
- Your vehicle is fitted with an anti-lock braking system. When should you check that it's working properly? Braking systems
- What will 'pumping' the brake pedal in a vehicle fitted with anti-lock brakes cause? Braking systems
- You're driving a vehicle fitted with anti-lock brakes. What should you do when braking in an emergency? Braking systems
- What should anti-lock brakes let you do when you have to stop in an emergency? Braking systems
- Your vehicle has anti-lock brakes. How does this affect you when you're braking normally? Braking systems
- You're driving down a long hill. What should you use to prevent the brakes from overheating? Braking systems
- What's provided specifically to protect you against neck and whiplash injuries? The driver
- When should an anti-lock braking system (ABS) warning light turn off? Braking systems
- What's the most powerful brake on a bus? Braking systems
Driving Instructor (ADI Part 1)
- What should you do if the warning light for your anti-lock braking system (ABS) stays on? Band 2 traffic signs and signals, car control, pedestrians, mechanical knowledge
- Which road surface may cause an anti-lock braking system (ABS) to be less effective? Band 2 traffic signs and signals, car control, pedestrians, mechanical knowledge
- You're driving on an icy road. What gap should you leave between your car and the car in front? Band 1 road procedure