What is adaptive cruise control?

It’s not a stretch to call cruise control one of the earliest driving aids. It wasn’t always electronic, and it certainly didn’t make your grandfather’s 1982 Cadillac Seville autonomous, but it was a revolutionary invention. (Although here’s a fun fact: Your grandfather’s Buick had the first infotainment system way back in 1986.)

Adaptive cruise control takes it to the next level. It maintains a set speed for your vehicle, like a conventional cruise control system, but it also adjusts the speed based on the traffic flow. Better systems can come you a full stop in heavy traffic and continue when congestion lightens. This technology can make cruise control more useful by taking some (but not all) of the workload off the driver. Here’s what it is, and how it works.

What to look for in an adaptive cruise control system

The concept is simple: Make the car accelerates and decelerates automatically depending on how quickly the cars around it are moving. The devil’s in the details, however.

To do it, a car must be equipped with sensors that allow it to detect nearby vehicles and potential obstacles. Most adaptive cruise control systems use radar, with high resolution radar on the horizon, although a camera and lidar (which works on the same principle as radar, but with light waves) can be used as well. You can often spot these cameras integrated into the grille or mounted behind the windshield. These sensors communicate with a computer that controls the throttle and, sometimes, the brakes and the steering system.

In its most basic form, adaptive cruise control technology only handles acceleration and deceleration, usually by following the car in front and maintaining a set following distance. Some automakers have started bundling this feature with a system that can bring the car to a full stop if needed, which comes in handy in a traffic jam, and/or one that provides a limited amount of steering assistance to keep the car centered in its lane.

Adaptive cruise control is at the center of the pile of electronic driving aids some automakers believe could form the basis of fully autonomous driving. We’re nowhere near autonomous cars, though, and it’s important not to mistake adaptive cruise control and other related technologies for full autonomy. These systems are designed to help the driver, not to drive the car themselves while the driver dozes off or counts blue cars going the other way.

Are there aftermarket adaptive cruise control systems?

This is one technology that cannot easily be retrofitted to an existing car. The complexity of adaptive cruise control systems puts them beyond the reach of the aftermarket. Considering that these systems can mean the difference between a car driving along and a car smashing into the back of another vehicle, concerns over liability will probably keep adaptive cruise control firmly within the domain of the original equipment manufacturers for the time being.

Who does adaptive cruise control best?

Cadillac

Like systems available from other automakers, Cadillac’s Super Cruise allows the car to accelerate, steer, and brake without driver intervention on highways. But Cadillac is the only automaker to specifically claim that drivers can take their hands off the wheel. That’s because Cadillac did a thorough job in setting up Super Cruise. Not only does the system rely on an array of cameras, radar, and lidar, but Cadillac also mapped 200,000 miles of highway. Super Cruise also has a driver-facing camera, and will only work if a certain level of driver alertness is maintained.

It’s too bad Super Cruise isn’t widely available, at least, not yet. Cadillac launched the system on its flagship CT6 sedan but has been slow to expand to other models. With the CT6 set to be discontinued, Cadillac finally announced that Super Cruise will be available on the CT4 and CT5 sedans when they go on sale in the coming months. Those sedans use a new electrical architecture that can support Super Cruise.

Subaru

Subaru’s EyeSight system uses cameras instead of radar, bringing down its cost and making installation of the hardware a bit easier. EyeSight bundles adaptive cruise control with lane-keeping assist, a “pre-collision throttle management” feature that cuts the throttle ahead of an anticipated collision, and low-speed autonomous emergency braking. On some models, Subaru has also added a driver-facing camera to ensure the driver stays alert while these features are in use.

Mercedes-Benz

Mercedes offers one of the most comprehensive adaptive cruise control and driver-assistance suites of any automaker. Its latest Distronic Plus system can keep up with traffic, but also brake the car to a full stop in stop-and-go situations. The system will automatically resume driving if the car remains stopped for less than three seconds; longer stops require a tap of the accelerator pedal or of the cruise control’s “resume” button. A steering-assist feature helps keep the car centered in its lane, and certain versions of the system can initiate lane changes.

Tesla

Tesla’s Autopilot system has attracted its share of controversy, and the name is a bit misleading considering that a human driver must be kept in the loop, but it’s still one of the most advanced systems of its kind. In addition to following traffic and automatically keeping a car in its lane, Autopilot can execute lane changes with the flick of a turn signal, and negotiate some highway off-ramps. Tesla’s ability to pull data from cars using the system and launch over-the-air software updates means Autopilot has significant potential to improve over time.

Volvo

It’s no surprise that an automaker obsessed with safety was an early adopter of adaptive cruise control. Volvo was also one of the first automakers to pair the technology with autonomous emergency braking, allowing a car to both automatically follow a vehicle in front and brake if it encounters an obstacle. Volvo’s latest Pilot Assist II system doesn’t need to track a vehicle ahead, can a keep a car centered in its lane, and can operate at speeds up to 80 mph.