Adaptive cruise control (ACC)

What is adaptive cruise control and how does it work?

Adaptive cruise control, or ACC, is cruise control that also keeps a distance. You choose a speed and a following distance. If a slower car is in front of you, ACC eases off the accelerator and brakes when needed. When the road is clear again, the car speeds up to your set speed.

A radar in the front measures the gap and the difference in speed. Often a camera behind the windscreen helps. How hard ACC can brake and whether it works down to a stop differs per car. Check your owner’s manual.

When ACC uses the brakes, your brake lights normally come on too. When it only eases off the accelerator, they usually do not.

When ACC is on, you see a symbol on the dashboard. Often it is a speedometer with a car in front of it, sometimes with bars for the distance. Every brand has its own symbol. Check the manual to see what it looks like in your car.

Difference between cruise control and adaptive cruise control

With normal cruise control you watch the gap yourself. With ACC you do too, the car just helps. For saving fuel with cruise control, see fuel consumption.

How to set the following distance on adaptive cruise control

In dry weather keep a gap of at least two seconds. In rain, fog or slippery conditions, keep more. The bars in the menu are not fixed metres or seconds. Your owner’s manual explains what they mean. So check with a fixed point beside the road that you have enough space. How to count it is explained under following distance.

Does someone merge just in front of you? ACC needs a moment to follow that car. The gap may become too small. Ease off and brake yourself when needed. Do not choose a short gap to keep merging cars out.

When should you not use adaptive cruise control?

ACC is a help, not an autopilot. Take extra care, or switch ACC off, in these situations:

• Bends and exits: without a car ahead, normal ACC keeps the set speed. Choose a safe speed yourself.
• A stationary traffic jam: not every system recognises stopped cars in time. Brake yourself.
• Bad weather: rain, snow, ice or dirt on the sensor can limit how it works.
• Roadworks and busy city traffic: the situation changes quickly there.

Does your ACC adjust the speed using signs or map data? That information can be wrong too. Read the signs yourself. Do you get an error message? Drive yourself and do not rely on ACC.

How to turn off adaptive cruise control

You usually switch ACC off by braking, or with the button on the steering wheel or stalk. Where that button is differs per car. Practise this before you drive, not on the road.

If you press the accelerator, you often go faster than ACC for a while. When you release it, ACC takes over again. After stepping in, check which speed is still set.

Is adaptive cruise control mandatory?

No. Adaptive cruise control is not a mandatory system. Many new cars do have it. Other systems are mandatory in new cars, such as automatic emergency braking and intelligent speed assistance (ISA). You may use ACC during the practical driving test. The examiner does check that you drive safely yourself. See the CBR Rijprocedure B (Dutch).