What is ACC (adaptive cruise control)?

  • We answer your questions on adaptive cruise control
  • How does adaptive cruise control work?
  • Does my car have adaptive cruise control?

Adaptive cruise control (or radar-guided cruise control) automatically adjusts the speed of your car in order to maintain a safe distance to the vehicle in front. The driver can pre-set their vehicle’s maximum speed and minimum distance to the car in front.

Cruise control has been around for decades, and in its basic form it’s now fitted to the majority of new cars as standard equipment. It’s a simple technology that holds a speed that you choose until you either cancel it or hit the brakes.

Most people use it to keep a steady 70mph on the motorway, so you can rest your feet and relax into a longer journey. Yet traditional cruise control can’t deal with traffic ahead - you need to step in if you see an obstruction and hit the brakes.

That’s where adaptive cruise control, also known as active cruise control or ACC, comes in. This is a new technology that’s fitted to more and more new models, either as standard or as an optional extra, and it can handle slowing down as well as speeding up.

How does adaptive cruise control work?

On a completely clear road, adaptive cruise control works the same as a normal cruise control set-up. It monitors the speed of the wheels, and adjusts the amount of power it needs to maintain a speed that the driver chooses using a stalk or control on the steering wheel.

But when there’s other traffic around, ACC can also adjust the speed to match that of a car in front. In most models a radar transmitter on the front bumper sends information to the car’s computer about how far away the car in front is, and then the correct amount of power from the engine (or electric motor) is set.

If the car in front slows down, your car will also slow down automatically, matching their speed. In some cars the system can go right down to a stop, and then pull away again when the traffic begins to move. This is often called ‘traffic jam assist’ or similar.

The driver can set the target speed, and when the car in front moves away, the ACC system accelerates up to that speed. The driver can also set how close they want their car to follow the car in front, up to a minimum of about two car lengths in most cases.

Some cars even have steering assist, which can keep you in your lane automatically. You have to keep your hands on the wheel, but the car gently steers itself to stay within the white lines. This is often called 'traffic assist' when it is designed to stop, start and steer at slow speeds - most widely available on cars from BMW and Mercedes.

Do I need adaptive cruise control?

If you do a lot of motorway miles, then adaptive cruise control could be a very worthwhile option to choose when buying a new car. It allows you to take your foot off the throttle pedal and this will help reduce leg pain on a long trip.

Adaptive cruise means you don’t have to use the brakes either, as the car does this automatically. It can help make traffic jams more relaxing. Adaptive cruise can only help at lower speeds in automatic cars, as in a manual you still have to change gear and use the clutch yourself.

Does my car have adaptive cruise control and how do I use it? 

If you’re buying a new car, check the list of standard equipment and the optional extras in the brochure to see which versions have this function, or if you can add it as an extra for a fee.

If you’ve already got a car and aren’t sure if it has ACC, check to see if you can change the following distance. If you can, then it’s an adaptive system. Cruise control buttons are usually found on a stalk behind the wheel, or on the wheel itself. You can check your car’s manual to find out what each individual button does and how to use it.

Which cars have adaptive cruise control? 

Adaptive cruise control started to become available after 1999, when the Mercedes S-Class gained 'Distronic'. Before then, earlier systems provided distance warnings or could control engine speed, but not apply the brakes - a crucial element for the system to work effectively in traffic.

MINI was one of the first to offer adaptive cruise on a small car, while Ford were in the first wave of it being included on an affordable, popular car in the Fiesta. It has become as widely available as electric windows or air conditioning, and the system is now available on humble family hatchbacks such as the Ford FocusVolkswagen Golf and Skoda Octavia.

It's one of the building blocks of autonomous self-driving technology, so expect this tech to continue proliferating.

Similar to

Radar-guided cruise control
Active cruise control
Traffic jam assistant

Looking for more jargon-busting motoring meanings? Head over to our Parkers Car Glossary page and take a look at our other definitions