Adaptive Cruise Control: How Does It Work?

By Russ Heaps 07/21/2022 12:00pm

Adaptive cruise control: How it works

When carmakers pitched cruise control to the American public more than half a century ago, they framed it as a way to maintain a safe, consistent speed on the highway and a path to conserving fuel. Although the fuel savings were minimal, both claims were accurate.

Simple to use, all you need to do is turn on the system in your vehicle, reach your desired cruising speed, and set it. The system then assumes control of the accelerator, maintaining the set speed until the driver engages the brake. Easy peasy.

Automotive engineers tweaked around the edges of cruise control for the next 35 years. However, cruise control didn’t evolve much beyond the first system that found its way into the 1958 Chrysler Imperial.

By the early 1990s, Japanese carmakers were adding a form of forward collision warning to their cruise control, but it was still up to the driver to react and apply the brakes. Not until Mercedes-Benz developed its Distronic cruise control did cruise control with self-braking make its first public appearance. Mercedes first featured it on its 1999 S-Class.

In essence, not only did the 1999 S-Class introduce the driver-aid technology adaptive cruise control (ACC), but it also set the cornerstone of the foundation for self-driving vehicles.

Cruise control is still the more prolific of speed controls offered on today’s new cars, but adaptive cruise control has started gaining ground. More car models provide it as standard or as an available option. But, what exactly is adaptive cruise control, and how does it work? Let’s see.

What Is Adaptive Cruise Control?

Adaptive cruise control systems vary in sophistication from carmaker to carmaker and sometimes even model to model. They also vary in name. For example, Genesis calls it Smart Cruise Control, while BMW identifies it as Distance Control. However, in a nutshell, the feature holds a safe preset speed while maintaining a safe following distance from the traffic before it. ACC essentially makes commuting and road trips so much easier.

Depending on the system, here’s what else the feature can do:

  • Set the distance. Most systems allow you to set the following distance within parameters like one, two, or three cars.
  • Stop the vehicle in traffic. Some ACC systems will bring the car to a complete stop if the traffic before it stops. However, they won’t self-accelerate when traffic begins moving again.
  • Stop and start in traffic. Some systems will bring the vehicle to a complete stop and then automatically accelerate as the flow of traffic resumes.
  • Work at low speeds in city traffic. Other systems use an add-on called traffic-jam assist designed to fully function in low-speed stop-and-go traffic found on city streets or logjammed highways.
  • Slow down at curves. Moreover, there are ACC systems capable of working with your vehicle’s GPS mapping to anticipate approaching curves, slowing the car going into the curve if it determines the preset speed is too high.
  • Adjust to speed-limit variations. Some systems working in conjunction with traffic-sign recognition or GPS will adjust the speed according to speed-limit variations.
  • Appear in head-up display. The ACC will show up in your view for vehicles equipped with head-up display.

How Does Adaptive Cruise Control Work?

Think of ACC as cruise control with a Ph.D. It can use radar, laser, binocular computer vision systems, a forward-aimed camera, or some combination of these technologies to track the traffic ahead of your vehicle. It senses when that traffic flow slows or stops, reacting to maintain the preset following distance.

As stated earlier, some systems will bring your vehicle to a complete stop to match traffic flow. Even more intelligent systems can then accelerate as the traffic flow resumes. These are called assisting, predictive, and multi-sensor systems.

Benefits and Limitations of Adaptive Cruise Control

Warming up to ACC required a long time for us. Early systems didn’t allow for presetting the maintained following distance. Consequently, a vehicle six or seven car lengths ahead of you moving into your lane became almost an airbag-deploying event. However, as ACC systems evolved and improved, we became more accustomed to them. We now look at regular cruise control as barbaric.


Reducing driver stress: No question, the number one benefit of ACC is allowing the driver to relax a bit. The system assumes the responsibility of slowing and accelerating to adjust to traffic flow. It doesn’t mean the driver gives up control, but the system assumes the workload of keeping pace with the traffic flow.

Stop and go: With more intelligent systems, ACC assumes complete control of braking and accelerating. In other words, it can bring the vehicle to a full stop and then accelerate as the flow of traffic resumes. Some systems will disengage after stopping and leaves it to the driver to push the “Resume” button or tap the accelerator to get moving again. However, more sophisticated systems will accelerate themselves from a complete stop.

Easy to use: For drivers not able (or willing) to read a car manual before setting out on the highway, you can fiddle with the ACC system and pick it up with little practice.


Not autonomous: Regardless of an ACC system’s sophistication, the driver must stay engaged. ACC can’t read the minds of vehicles around it. It only reacts to what other cars do. Anticipating the actions of other drivers remains your responsibility.

No stop and go: ACC systems that don’t offer a full stop will slow the vehicle but require the driver to bring it to a full stop when the flow of traffic stops. Even if an ACC system does bring the vehicle to a full stop, it may still require the driver to re-engage the system to get back under way.

No lane change: An ACC system itself can’t change lanes automatically to maintain the preset speed. Therefore, if you’re not paying attention as the driver, you may find your vehicle is going several miles an hour below the set speed. This is because your vehicle has gradually pulled up behind a slow-moving car, and you have steadily slowed to its pace. This is another reason you should stay engaged.

What Is the Difference Between Adaptive Cruise Control and Self-Driving?

There continues to be plenty of confusion about self-driving or autonomous systems, what they are, and how they operate. We’ll get to that next. However, the major difference between adaptive cruise control and a self-driving system is, ACC is simply a component of a driverless system. That is to say, ACC provides automatic braking and acceleration in a self-driving system that also includes steering, and sometimes automatic lane changing.

What Is the Difference Between Level 2 and Level 3 Autonomous Driving?

SAE Levels of Automation

We won’t take you through all levels of driving automation. They begin with no automation and wrap up with full automation, including vehicles without pedals or steering wheels. See the chart above from SAE International.

What we will contrast is Level 2 and Level 3. Spoiler alert: The difference is significant.

Level 2 – To qualify as Level 2, a vehicle must have at least two driver-assistance technologies. This typically includes ACC and another technology like lane-centering assist or lane-keeping assist. With these technologies, the vehicle can steer, accelerate, and brake on its own in certain conditions. Level 2 still requires the driver’s hands on the wheel and eyes on the road. It is the current state of automation.

Level 3 – If Level 2 is partial self-driving, Level 3 is conditional full automation. A Level 3 self-driving system uses a wide spectrum of driver-assistance features and artificial intelligence (AI). These technologies collude to react to and make decisions about the vehicles’ ever-changing situations. In a Level 3 vehicle, the driver can completely surrender control of the vehicle’s operation on specific roads. The driver must be prepared to resume control in case of an emergency but otherwise doesn’t have command of the car. That is, the driver’s hands can be off the steering wheel and their attention elsewhere.

Although the state of autonomous driving today is Level 2, a few carmakers are on the precipice of Level 3. For example, Tesla’s Enhanced Autopilot, Ford’s BlueCruise, the Mercedes Drive Pilot, and General Motors’ Super Cruise bring the potential for Level 3. A few over-the-air software tweaks will turn the potential into reality. However, like a stood-up date who is all dressed up with nowhere to go, you will not find Level 3-designated highways as of yet.

What Carmakers Call Their Adaptive Cruise Control Systems

Is anyone surprised that carmakers can’t seem to agree on a single term for adaptive cruise control? How about “adaptive cruise control?” We can sort of forgive Mercedes for its Distronic cruise control. It was first, after all. However, can someone define “distronic?” Anyone, anyone? Nope because it’s a made-up word. So, why not now use adaptive cruise control? Mercedes isn’t alone. Many carmakers use unique terms for ACC. Some call it adaptive cruise control as the root and then tack something onto it.

Here’s a rundown of the terms the various carmakers use for ACC, even those that simply call it adaptive cruise control.

  • Acura – Adaptive Cruise Control with Low-Speed Follow
  • Alfa Romeo – Adaptive Cruise Control Plus with full stop
  • Aston Martin – Adaptive Cruise Control
  • Audi – Adaptive Cruise Control with Stop and Go
  • Bentley – Adaptive Cruise Control
  • BMW – Distance Control
  • Buick – Adaptive Cruise Control
  • Cadillac – Adaptive Cruise Control
  • Chevrolet – Adaptive Cruise Control
  • Chrysler – Adaptive Cruise Control with Stop and Go
  • Dodge – Adaptive Cruise Control
  • Ford – Adaptive Cruise Control with Stop-and-Go
  • GMC – Adaptive Cruise Control
  • Genesis – Smart Cruise Control
  • Honda – Adaptive Cruise Control
  • Hyundai – Smart Cruise Control with Stop and Go
  • Infiniti – Intelligent Cruise Control
  • Jaguar – Adaptive Cruise Control
  • Jeep – Adaptive Cruise Control with Stop and Go
  • Kia – Smart Cruise Control with Stop and Go
  • Land Rover – Adaptive Cruise Control with Stop and Go
  • Lexus – Dynamic Radar Cruise Control
  • Lincoln – Adaptive Cruise Control with Stop-and-Go
  • Lucid – Adaptive Cruise Control with Speed Limit Assist
  • Maserati – Adaptive Cruise Control with Stop and Go
  • Mazda – Mazda Radar Cruise Control with Stop and Go
  • Mercedes-Benz – Distronic Plus
  • Mini – Adaptive Cruise Control
  • Mitsubishi – Adaptive Cruise Control
  • Nissan – Intelligent Cruise Control
  • Polestar – Adaptive Cruise Control
  • Porsche – Adaptive Cruise Control
  • Ram – Adaptive Cruise Control with Stop, Go and Hold
  • Rivian – Adaptive Cruise Control
  • Rolls Royce – Active Cruise Control
  • Subaru – Advanced Adaptive Cruise Control
  • Tesla – Traffic-Aware Cruise Control
  • Toyota – Dynamic Radar Cruise Control
  • Volkswagen – Adaptive Cruise Control
  • Volvo – Adaptive Cruise Control

Is Adaptive Cruise Control Worth It?

We say yes. This is particularly true if you do a lot of highway driving. Moreover, the more sophisticated systems with full stop and start or a low-speed traffic-jam feature work great for city driving. Typically, ACC gets included in a trim level or some sort of optional driver-assistance package on new cars. You will rarely find it listed as a stand-alone option.

For example, the Hyundai Elantra SEL ($22,795 with destination fee) offers its Smart Cruise Control with Stop and Go in its optional Convenience Package ($1,900). It also includes forward collision warning with automatic emergency braking, Junction-Turning Detection, navigation, wireless phone charging, heated front seats, and more. We’d say that’s a bargain. On the other hand, the same ACC system is standard for the $27,395 Elantra Limited.

Can I Add Adaptive Cruise Control to My Car?

Yes, you will find aftermarket adaptive cruise control kits available. Depending on the features, they range in cost from $250 to nearly $4,000. That’s just the cost of the kits. The installation will add even more. For most involved electric-system installations, it’s best to get them done by a dealership or certified mechanic. We believe that’s the case with an ACC system. Installation cost depends on the sophistication of the system and the vehicle model.