What is an Anti-lock Braking System (ABS)?

Last updated September 29, 2022

If you’re a fully licensed driver, there’s a good chance you’ve already heard the term ‘Anti-lock Braking System’ (ABS). For those unfamiliar, an ABS is a universal safety feature found in modern cars designed to prevent skidding, especially in demanding braking scenarios.

In this article, we will cover how ABS systems work, how to use them, their capabilities - and limitations. We will also explore the laws and regulations concerning ABS, the history of their development, the various ABS issues that can arise – and how to resolve them.

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What do anti-lock brakes do?

An ABS makes it easier for you to steer in emergency braking situations by restoring traction to the tyres. By preventing the wheels from locking, an ABS can help the driver retain control of the vehicle.

How to use Anti-lock Brakes in an emergency?

To activate your car’s ABS, apply (and hold) pressure to the brakes. You should also steer to avoid any hazards, if necessary. Maintain pressure on the brakes until you have either slowed down to a safe speed or come to a complete stop.

Do I still need to pump my brakes when driving a car with ABS?

When driving an ABS-enabled vehicle, there is no need to pump your brakes. Your ABS will automatically pump the brakes the moment it detects wheel skid. All you need to do is apply firm, steady pressure to the brake pedal. The pedal should then pulsate while the ABS light illuminates.

Are anti-lock brakes a legal requirement?

Anti-lock braking systems have been compulsory for all production cars in the UK since 2004. Any car from the UK market built after this time will have ABS fitted as standard. ABS for new vehicles was made compulsory by EU law for safety reasons and has saved many lives since being introduced.

Can ABS be added to my car?

Yes, ABS can be retrofitted to virtually any car – and this should improve the vehicle’s safety as well as reducing the likelihood of accidents. This should be carried out by a reputable mechanic to ensure the system is correctly installed.

However, before committing to having an ABS added to your car, you should consider whether the work is economically viable. ABS conversions can be expensive and may even exceed the value of your car.

To help you determine whether this would be a worthwhile project, you can use our free car valuation tool. And, if you decide that selling your vehicle is the way forward, we can also arrange to buy your car.

How does an Anti-lock Braking System work?

The ABS senses when the wheels are about to lock, then reduces and adds braking pressure many times per second, so that the right amount of pressure is applied. This ensures the wheels continue moving as the vehicle slows, avoiding wheel lock.

When will my anti-lock brakes take effect?

Anti-lock brakes take effect when the sensors, placed by each individual wheel, detect that the wheels are about to lock.

What are the components of an ABS system?

An Anti-lock Braking System comprises four components, which work together to deliver more braking power and control:

Speed Sensors

The speed sensors, which are located at each of the wheels (or sometimes, the differential) are used to detect when wheels are just about lock up.


In an ABS-enabled car, there is a valve in the brake line for each brake, which is controlled by the ABS. In many cases, this valve has three positions:

  • The valve is open and pressure from the master cylinder is passed straight through to the brake.

  • The valve blocks the line, which isolates the break from the master cylinder and prevents pressure from rising further if the driver applies more pressure to the brake pedal.

  • The valve releases pressure from the brake.


Whilst the valves can release pressure from a brake line, the pump can reapply it whenever needed.


The controller is a computer system that monitors the speed sensors and controls the valves accordingly.

When are anti-lock brakes most effective?

Anti-lock brakes are most effective when applied firmly and promptly on dry, solid surfaces, and when the vehicle has good contact with the road. For your ABS system to work well, the tyres should also be properly inflated and in good overall condition.

When are anti-lock brakes least effective?

Anti-lock brakes are less effective when road contact is poor and on surfaces such as mud, snow or gravel. However, so long as the tyres and the rest of the vehicle are in good working order, your ABS should still provide enhanced braking control in these conditions.

Which vehicles have ABS?

All UK production cars manufactured since 2004 are fitted with ABS as standard, as this was made mandatory by UK law. Some models manufactured before then do not have ABS. However, many older models do have ABS fitted, as the technology has been available since the 1960s.

How do I know if I’m driving a vehicle with anti-lock brakes?

If your car has anti-lock brakes, you’ll notice the system working when you push the brake pedal down and the car judders as it slows. This is due to the ABS rapidly applying and releasing across all four wheels to avoid skidding.

Rear-wheel only ABS

Some older vehicles, particularly pickup trucks have rear-only ABS. Aside from being cheaper for manufacturers, rear-wheel ABS helped to prevent the lighter end of the vehicle from swinging during harsh braking.

Rear-only ABS was more common among cars in the US market, until full ABS became mandatory for all new production cars sold in the United States in 2013.

Pros and cons of ABS

Advantages of ABS

Cars with Anti-lock Braking Systems offer several advantages over those without. Firstly, they are far less prone to wheel lock and skidding, even in slippery conditions, where drivers may otherwise lose control. They are also highly effective in emergency stop scenarios, as the ABS will prevent the brakes from locking.

Thanks to the enhanced steering and braking control it provides, ABS technology can enhance your car’s value. And, thanks to the improved safety, many insurers offer cheaper rates for vehicles with Anti-lock Braking Systems.

Disadvantages of ABS

In most circumstances, anti-lock brakes provide a good level of braking control. However, stopping distances can be inconsistent on various surfaces and in differing conditions.

The sensors on each wheel can be costly to repair or replace should they become faulty. The electronic components are also sensitive and repair bills can run high if they become damaged.

The history of Anti-lock Braking Systems

The first ABS system was developed by Dunlop in the 1950s for aviation applications. It improved stopping distances when landing and virtually eliminated wheel lock. The first car with ABS was the 1966 Jensen FF, which was unwieldly, and the hydraulic system didn’t translate well to vehicular use.

However, as electronic technology improved, in the 1970s and 80s, more responsive ABS systems were available with models from popular manufacturers such as Bosch and General Motors. In 1985, the Ford Scorpio was the first car to be sold with ABS as standard across the entire range.

What is cadence braking?

Cadence braking (also ‘stutter braking’) is a driving technique for performing emergency stops that was widely taught by driving instructors before shrinking numbers of non-ABS cars on the road rendered it largely obsolete.

Is cadence braking still necessary?

Providing your car has a working ABS system, cadence breaking isn’t necessary. In an emergency stop situation, hit the brakes and the system’s electronics will handle the rest. Cadence braking is still useful for driving non-ABS vehicles, but switching to anti-lock braking is the safer option.

Other Frequently Asked Questions

If your ABS isn’t working, you will still be able to brake, providing your brakes are still operational. You should take extra care, however, as you won’t have the same level of control when braking heavily. Consider taking your car to a reputable garage for ABS repairs.

If your ABS is faulty, you will notice a difference when braking harshly. Your brakes may lock, even when braking gently. If the ABS light appears and stays illuminated, this can also indicate the module is faulty or has failed. A failing ABS may also affect stability or traction control.

In many cases, an Anti-lock Braking System can be repaired. This may involve repairing or replacing the control module, or other components, such as the wheel sensors. If you’re experiencing issues with your ABS, you should consult a trusted local garage.

The cost of repairing an ABS will vary depending on the components affected and the severity of the damage. The replacement cost for a single wheel speed sensor is typically around £220. If multiple sensors are damaged, restoring the ABS to working order can be costly.

If the repair costs are not feasible, you may decide to sell your scrap car to a car buying service such as webuyanycar or an ATF (Authorised Treatment Facility).

The ABS symbol illuminates on the dashboard of cars with Anti-lock Braking Systems. The symbol features the ‘ABS’ acronym, which is often surrounded by a circle with two curved lines on either side.

Common reasons why the ABS light illuminates include the ABS module not functioning properly, low levels in the fluid reservoir, broken wheel sensors – and the ABS system being deactivated. If this issue persists, you should consult an experienced mechanic.

If your ABS light illuminates permanently (it will typically flash when starting your car), the vehicle will fail its MOT. You may also fail your MOT if the ABS light illuminates during the brake efficiency test, as this signifies the system is not working as it should.