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Does my car have anti-lock brakes?

You can't see anti-lock brakes, so a reasonable question may be how can I tell if my car has anti-lock brakes?

Whilst starting your car or turning the ignition on an ABS symbol / light will illuminate on the dashboard and extinguish moments later if ABS is fitted. See below for ABS dashboard symbol.

All cars made for the European Union after July 2004 must legally have anti-lock brakes fitted. So if your car is newer than July 2004, it will have ABS.

Another indication that your car is fitted with ABS is if you have ever braked hard and felt a pulsating, juddering sensation on the brake pedal. This may be accompanied by a strange groaning noise. This is normal and is simply the ABS system activating.

Finally, if you have a vehicle owner's manual, this will tell you if ABS is fitted to your vehicle.

If an ABS light stays on, will it fail an MOT?

Immediately after engine ignition, the ABS light should stay on for a few seconds only and extinguish. If the light remains illuminated, a vehicle will not pass the MOT and fail until the cause is diagnosed and fixed. A faulty ABS is often due to corroded sensors.

It's often cost effective to have MOT failing vehicle defects repaired at your own convenience and at a garage of your choice before undertaking an MOT test. For further information on what an MOT test involves, see what is an MOT test.

Anti-lock brakes noise and vibration

Certain anti-lock brakes produce a noise, vibration and pulsating feel to the brake pedal. Particular systems are prone to more noise and vibration than others, but this is perfectly normal and indicates that the ABS system is functioning and active.

The pulsating sensation that may be felt on the brake pedal is the ABS applying and releasing pressure to the brakes.

Anti-lock brakes failure

If your anti-lock braking system fails, you will receive a warning light on your dashboard. This may be orange or red. See dashboard warning lights for further information.

There is no need to panic however as your normal hydraulic brakes are unaffected and you will be able to slow down and stop as normal. In an emergency braking situation however, there is the potential to lock the wheels and skid due to the ABS being inactive, so take your vehicle to your nearest dealer for repair at your soonest convenience.

Are braking techniques needed with ABS?

Good braking techniques are still essential to remain safe on the road, regardless of whether a vehcile has ABS or not. Progressive braking is a a safe driving technique, which

  • allows for other drivers to react to your actions
  • prevents locked wheels
  • prevents the car from skidding
  • reduces wear on the brakes, tyres, suspension and other mechanical parts
  • saves on fuel
  • is more comfortable for your passengers



Anti-lock braking system ABS

Anti-lock braking system or the commonly known abbreviation 'ABS' were introduced as standard on many cars during the mid-1980's.

What do anti-lock brakes do?
Drivers when faced with an emergency situation inevitably slam on the brakes as hard as possible in a desperate attempt to stop the car in the shortest distance. In a car without anti-lock brakes, this procedure typically locks the wheels and initiates a skid.

A skid renders a car out of control because the tyres have lost traction with the road surface, therefore reducing the ability to come to a stop in a quick and controlled manner.

During a skid the wheels will be locked and under these circumstances, the ability to steer the vehicle is almost entirely impossible. As the name suggests, anti-lock brakes prevent the wheels in most circumstances from locking.

Why are anti-lock brakes important and safe?

If the tyres of a vehicle are not skidding, then there is traction between the rubber and the road surface and therefore control. A vehicle will come to a stop much sooner if brakes under as heavy load as possible, whilst maintaining traction with the road surface.

Anti-lock braking system (ABS) dashboard warning light
Anti-lock braking system (ABS) dashboard warning light

As anti-lock brakes prevent the wheels from locking, it is also possible to steer the vehicle in an emergency stop procedure, potentially allowing a driver to steer away from an otherwise inevitable collision. How do anti-lock brakes work?

Almost all modern cars have computer systems on board. Part of this system controls the braking in the form of anti-lock brake control modules. Car manufacturers have their own ABS, some that work a little differently from others. Essentially however, sensors detect the wheel speed to determine if any of the wheels are trying to lock-up under braking. If the computer determines that one or more wheels are attempting to lock-up, hydraulic valves reduce braking to an affected wheel, or all wheels if necessary.

Does ABS stop you faster?

ABS will most likely stop you faster if compared to a vehicle without ABS that is skidding due to locked wheels in slippery wet conditions. Generally speaking however, it's a popular misconception that anti-lock brakes make you stop faster than a vehicle without. The primary purpose behind ABS is to avoid wheel locking so as to remain in control of the steering and therefore ABS won't make a car stop faster compared to one without. Rather than ABS making you stop faster, there are however some conditions where having ABS can make you stop slower.

Is ABS good in snow?

Harsh braking in snow is one example where ABS may take a vehicle longer to stop compared to a vehicle without ABS. If the wheels become locked on a vehicle without ABS, they can act in a similar way to a plough allowing snow to build up and accumulate in front of the tyres which in turn causes friction slowing the vehicle down. In loose snow, locked wheels may also dig-in and make contact with the tarmac. A similar affect can be said whilst braking on gravel. A car fitted with ABS however will remain on the surface due to the wheels not locking, potentially increasing stopping distances.

That being said, it's never ideal to lock the wheels due to loss of steering ability, even in slippery conditions such as snow. A high level of anticipation and planning is required to safely drive in snow and ice regardless of the braking system a vehicle has.

For further information and continued reading, see how to drive in snow safely

How to use anti-lock brakes

A cars brakes that utilises the anti-lock braking system is very easy to use. Simply exert firm and constant pressure onto the brake pedal until the vehicle has stopped. There is no need to pump the brake pedal. Remember however, the point of ABS is the ability to steer and not to stop sooner.

If braking in an emergency with ABS, apply firm pressure onto the brake pedal and if possible depress the clutch. ABS only works whilst the engine is running, depressing the clutch will aid in avoiding engine stall. As you have the ability to steer, look for an escape route rather than colliding with a vehicle in front. Focus your observation on the escape route and not obstruction you are trying to avoid. Steer away from the obstruction to the escape route.

How to test ABS

It's a good idea to test your anti-lock brakes to get a feel of what it like to stop in an emergency situation. Driving Standards Agency practical driving tests involve a simulated emergency stop.

Use the method described above but ensure you choose a straight and quiet road which is clear of other traffic and pedestrians. The DSA emergency stop procedure tutorial offers a guide to the manoeuvre that driving examiners expect.

Anti-lock brakes theory test questions

The DSA driving theory test covers a wide variety of questions, some of these related to braking and the use of anti-lock brakes. The information contained on this page will provide you with the knowledge necessary to pass anti-lock brake questions in the theory test. Test your anti-lock braking theory test knowledge by answering the questions below.

Question 1. Anti-lock brakes are at their most effective when you

  • Using the handbrake to reduce the stopping distance

  • Apply constant and firm pressure to the foot brake until you have stopped

  • Brake normally, but grip the steering wheel tightly

  • Continuously pump the foot brake to prevent skidding

    Theory test knowledge and understanding

    Anti-lock braking system is disabled when releasing the foot brake. Emergency braking requires firm and constant pressure on the foot brake until the vehicle has stopped.

Question 2. Anti-lock brakes are of most use when

  • Braking normally

  • Braking excessively

  • Driving on highly worn tyres

  • Braking gently

    Theory test knowledge and understanding

    Anti-lock brakes only become active under heavy braking and are not necessary under normal braking. Continuous anticipation and planning is required whilst driving to avoid sudden and unexpected situations that may require excessive braking.

Question 3. Anti-lock brakes are designed to assist the driver with the ability to

  • Control the car better under accelerating

  • Stop sooner

  • Brake later

  • Steer under heavy braking

    Theory test knowledge and understanding

    Without anti-lock brakes a vehicles wheels will lock under harsh braking. Locked wheels prevent steering control. The primary purpose of anti-lock brakes is to enable the driver to maintain steering control of the vehicle under emergency braking.

Question 4. Anti-lock brakes may not work as effectively on

Choose two answers

  • Dry road surfaces

  • Wet road surfaces

  • Loose snow road surface

  • Loose gravel surface

    Theory test knowledge and understanding

    Under most circumstance anti-lock brakes are highly effective at stopping a vehicle quickly whilst maintaining control. It may however take longer to stop in a vehicle with ABS on loose road surfaces such as snow or gravel.

Question 5. Anti-lock brakes prevent the wheels from locking. The benefits of this are

  • Little chance of a skid

  • Reduction in tyre wear

  • Better road grip

  • Less likely to puncture

    Theory test knowledge and understanding

    Under most circumstance anti-lock brakes are highly effective at stopping a vehicle quickly whilst maintaining control. It may however take longer to stop in a vehicle with ABS on loose road surfaces such as snow or gravel.

Question 6. Anti-lock brakes can significantly reduce the chance of a skid occurring particularly when

  • Driving at high speeds

  • Driving down steep hills

  • Heavy braking in an emergency

  • Normal braking

    Theory test knowledge and understanding

    Anti-lock brakes activate only under heavy braking conditions such as in an emergency.

Question 7. When do anti-lock brakes begin to work

  • Each time the brake pedal is pressed

  • On road surfaces with little grip

  • Just as one or more wheels begin to lock

  • Only at higher speeds

    Theory test knowledge and understanding

    During normal braking, a vehicles standard hydraulic brakes slow and stop the car. ABS is only activated if one or more of the vehicles wheels begin to lock.

Question 8. It's impossible to skid if a vehicle is fitted with anti-lock brakes

  • True

  • False

    Theory test knowledge and understanding

    Anti-lock brakes are designed to reduce the chances of skidding. However, if a vehicle is traveling too fast for the road and weather conditions, the vehicles inertia will cause loss of traction to the road surface and anti-lock brakes will become ineffective.

Question 9. The purpose of anti-lock brakes are to

Choose two answers

  • Maintain steering control whilst braking in an emergency

  • Reduce stopping distance

  • Reduce the chances of skidding

  • Brake much later due to little chance of skidding

    Theory test knowledge and understanding

    Anti-lock brakes purpose is to allow a driver steering control under heavy braking due to the wheels not locking and to reduce the chances of skidding. ABS does not reduce stopping distance in most cases and ABS should not be used as a means to brake later.