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 is an increasingly common feature on new cars in the UK and, as with many driver-aid systems, is very safe to use once you know exactly how it works. It’s popular with motorway drivers because it allows you to relax your right foot and can even help drivers avoid penalties for speeding, particularly in scenarios such as average-speed checks. Cruise control can be found in all types of car, including those with a manual gearbox.
Although cruise control was originally invented in the US over 70 years ago, it has only become common in the UK in the past few decades. It was once classed as a luxury, but can now be found in any kind of car.
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 a car’s system works can differ from model to model. Some systems also won’t function below a certain speed, usually 20mph.
How does cruise control work?
Cruise control keeps your car at a set speed of your choice. This system is particularly useful on long motorway journeys, because it allows you to rest your right foot rather than keeping it flexed in the same position for long periods of time.
The controls associated with cruise control are often located on the steering wheel or a column stalk, so that they can be reached as easily and safely as possible. Regardless of how a particular system works, pressing the brake pedal will immediately override any cruise-control system for safety reasons.
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: 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: 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: Pressing this will see the car accelerate back up to the speed you chose before hitting the cancel button or pressing the brake pedal. 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 or ‘+’ 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 5mph or even 10mph. Of course, this varies from one model to another.
Can cruise control save me money?
While cruise control’s primary job is to 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 cars are fitted with a speed limiter, either alongside cruise control or on its own. As with 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 but without exceeding 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 that was first seen on more expensive cars but is 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 the system will 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 your car catches up with another vehicle.
Auto makers have their own names for ACC, with Mercedes calling it ‘Distronic Plus’ and Porsche ‘Porsche Active Safe’. Some vehicles such as the Volkswagen Passat even have Traffic Jam Assist, an extension of adaptive cruise control that can automatically slow the car to a halt as well as 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.