What is cruise control and adaptive cruise control?
In this guide, we explain cruise control, speed limiters and ‘adaptive’ cruise control and how they function
Cruise control on a car will keep your vehicle at a set speed so that you don’t have to keep your foot on the accelerator. It was invented in the US over 70 years ago but has only become common in the UK in the last two decades. It’s popular with motorway drivers not only because it allows you to relax your right foot, but also because it can help drivers avoid penalties, particularly in scenarios such as average speed checks.
Cruise control systems can be a little daunting if you’ve never used them before, which is why you should always check your handbook before setting off; how they work differs from model to model. Some systems don’t work below a certain speed, usually 20mph.
According to a Carbuyer poll, 20% of drivers with cruise control don’t use it because they don’t know how it works. However, it’s worth learning, as it has the potential to make journeys more economical, less arduous and more comfortable.
How does cruise control work?
The purpose of cruise control is for the car to stay travelling at a speed of your choice, regardless of hills or gusts of wind, all with your right foot resting on the carpet. In almost every car, the controls for this are on the steering wheel or a column stalk so you can reach them as quickly and safely as possible. It’s also important to remember that in any car with cruise control – regardless of exactly how it functions – you can always override it by pressing the brake pedal.
These are typical cruise control buttons:
On/off: This simply activates the system, but probably won’t hold you at your desired speed. Turning it on will almost always be accompanied by a dashboard light.
Set button: Once the system is switched on, pressing the set button should tell the car to hold the current speed. In most cars this will turn the dashboard indicator green.
Cancel button: This pauses the cruise control, so you have full control again, without turning cruise control fully off. The cruise control should still remember the speed you chose to cruise at.
Res or resume button: Pressing this will see the car accelerate back up to the speed you chose before hitting the cancel button. In a manual car, you'll still need to change gears yourself if necessary. An automatic gearbox will select the most appropriate gear for your desired speed, for an even more relaxed experience.
Up and down arrows (also ‘+’ and ‘-’): With cruise control activated, use these to raise or lower the car’s speed. Single presses often increase or decrease the speed in small increments, while holding the same button or stalk changes it in increments of 5 or even 10mph. Of course, this varies from one model to another.
Remember, pressing the brake or accelerator pedal will override the system, although not switch it off entirely. Pressing the resume button will reactivate it.
Can cruise control save me money?
While cruise control’s primary job is take the stress out of driving, it’s possible that by smoothing out acceleration and deceleration, it can save fuel, too. On the other hand, some experts believe these systems aren’t very fuel-efficient on inclines and descents, making savings so small you probably won’t notice them.
The main reason motorists can see a cost saving is because cruise control helps them stick to a fuel-efficient speed. This is particularly the case on long motorway drives, where it’s easy to let your speed fluctuate.
What is a speed limiter?
Some models may be fitted with cruise control and a speed-limiter, or just a speed-limiter. Like cruise control, you set the maximum speed you’d like to travel at, but unlike cruise control, you're still required to press down the accelerator. This is ideal for busy speed-limit zones, where you may want to maintain full control of your speed in heavy traffic, but don’t want to exceed the limit. Squeeze the accelerator and your car will simply reach your chosen speed and stop accelerating. However, pressing the throttle pedal all the way down will override the system.
What is adaptive cruise control?
Often abbreviated to ACC, adaptive cruise control is a recent development first found on expensive cars but now finding its way to cheaper models. It’s a significant improvement on cruise control, since it uses lasers or a radar mounted at the front of the car to match your speed with that of the vehicle in front. You can also set a distance from the vehicle that you’re happy with and it’ll maintain it.
However, only systems that are paired with an autonomous emergency braking system will automatically perform an emergency stop if the car ahead comes to a halt.
Fortunately, if the car ahead suddenly shoots off, the system won’t follow suit. Instead, it holds the speed you set yourself, until you change it or it catches up to another vehicle.
Carmakers have their own names for ACC, with Mercedes calling it Distronic Plus and Porsche ‘Porsche Active Safe’. Some vehicles like the Volkswagen Passat even have Traffic Jam Assist, an extension of adaptive cruise control that can automatically slow the car to a halt and accelerate and brake at low speeds in congestion, reducing driver fatigue. It’s worth noting that after coming to a halt for more than a few seconds, safety requirements mean driver intervention is usually required; squeezing the accelerator should allow Traffic Jam Assist to resume.