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Adaptive cruise control: What is it, and how does it work?

If the vehicle ahead slows down or someone cuts into your lane, the car eases off the accelerator or uses the brakes to slow down and keep an appropriate distance.

5 months ago
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Derek Fung
Journalist

Adaptive cruise control is a natural, useful extension of cruise control, where you set a speed and the car maintains it until told otherwise, such as when the brakes or cancel button are pressed.

Classic cruise control is most useful on a long, relatively straight piece of highway when there aren’t too many cars around. 

With more vehicles about, maintaining a safe distance by toggling a wand or fiddling with buttons can be more work than manually operating the accelerator.

That’s where adaptive cruise control comes in handy. 

With an adaptive cruise control system the car tries to maintain your chosen speed, but will also keep a safe distance to the car in front. 

If the vehicle ahead slows down or someone cuts into your lane, the car eases off the accelerator or uses the brakes to slow down and keep an appropriate distance.

Often you can tell the system whether you want that distance to be big, small, or somewhere in the middle.

With many Australian states adopting draconian speed limit enforcement policies, adaptive cruise can also be an effective way to avoid demerit points and keep cash in your wallet.

With that said, some carmakers allow their systems to drift over the set speed when travelling downhill.

Abilities and limitations

On many older cars and some lower-end current models, the adaptive cruise control system only operates above a threshold speed, often 30km/h or 50km/h. 

If the car in front drops below the system’s limits, an alarms goes off and the driver is told to take over.

In vehicles where autonomous emergency braking isn’t installed,  if the car in front decelerates too quickly for the system to handle, an alert will sound and a message will appear in the instrumentation panel asking the driver to intervene.

From standstill

More advanced systems, sometimes labelled “all speed“, work from any speed and can bring the car gradually to a complete stop, but require the driver to press a button or touch the accelerator to start the car rolling again.

In cars offering “stop and go” functionality, the system is able to restart itself when the car in front starts moving again.

It should be noted adaptive cruise is designed primarily for congested freeway or highway situations.

If you happen to be using it on a regular suburban road and encounter a stop sign, traffic light or road diversion, it’s up to you to navigate these obstacles safely.

Adaptive cruise control: What is it, and how does it work?

The name game

As with so many automotive technologies, automakers have not agreed on a single name for adaptive cruise control and its different permutations.

Common alternatives to the phrase adaptive cruise control include active cruise control, smart cruise control, dynamic cruise control, radar-guided cruise control, or some amalgam of these words.

Some carmakers, such as Mercedes-Benz, go one step further and have come up with their own branding: Distronic Plus.

How does it work?

For adaptive cruise control to work, the car needs to be able to “see” in front it. 

This is typically done with a radar, which bounces a radio waves off objects ahead to determine their distance. By measuring how long it takes for those waves to return, the cruise system can determine how far away the car in front is.

Do this regularly enough, and radar can also figure out how fast that vehicle is travelling. Automotive radar units are usually hidden in the grille or the lower air intake.

Some manufacturers also use a camera, or cameras, to augment the data the car receives from the radar system.

Adaptive cruise control: What is it, and how does it work?

Autonomous Driving

If you take adaptive cruise and combine it with some of the safety systems found on some newer cars, such as lane-keeping assist, traffic sign recognition and autonomous emergency braking, and you have the ingredients for a basic self-driving system.

Overseas, some manufacturers are offering Level 2 self-driving systems, with Cadillac’s Super Cruise and Nissan’s ProPilot capable of autonomously driving vehicles along a single lane on freeways and motorways.

Both systems rely on GPS connectivity and high-definition mapping.

When using Nissan’s system, you program self-driving start and end points into the navigation system, while Cadillac’s setup is activated through the adaptive cruise system, but only works on a pre-approved highways within the USA and Canada.

In addition to further questions you might have, let us know about your experience, likes, and dislikes with adaptive cruise control in the comments.


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