What is Adaptive Cruise Control, and How Does It Work?

An important step on the road to driverless cars

An overhead view of traffic illustrating adaptive cruise control
Michael H / Stone / Getty

Adaptive cruise control is the answer to the biggest problem that cruise control has suffered from ever since it was introduced. While cruise control can help you maintain a constant speed on the highway, and even increase your fuel economy, it's useless in traffic. Adaptive cruise control fixes that by automatically adjusting the speed of your vehicle to match the flow of traffic.

What is Adaptive Cruise Control?

Also referred to by terms like autonomous cruise control and radar cruise control, adaptive cruise control is essentially the natural evolution of legacy cruise control systems, augmented with additional technologies to provide a safer, less hectic driving experience

These systems are capable of automatically adjusting the speed of a vehicle to match the speed of the car or truck in front of it. This allows vehicles equipped with adaptive cruise control to respond to the actions of other drivers without requiring any additional input.

The driver of a vehicle equipped with adaptive cruise control need only set their desired speed, and then make sure that their vehicle stays in its lane. When the adaptive cruise control detects that a vehicle in front has slowed down, it can adjust the throttle, and the brakes if necessary, to automatically match it. When traffic picks back up, these automatic systems are also capable of acceleration.

How Does Adaptive Cruise Control Work?

Cruise control is a relatively simple system that allows a driver to adjust the position of the throttle without using the gas pedal. It has been around for a very long time, and it often helps improve fuel economy at highway speeds.

The main issue with cruise control has always been that drivers who use these systems have to remain constantly vigilant against the actions of other drivers. Most cruise control systems will shut off if the driver taps the brakes, but they aren’t capable of making automatic adjustments to the speed of a vehicle.

Adaptive cruise control is similar in design to more traditional systems, but there are a few additional components in play.

Instead of relying solely on driver input, adaptive cruise control systems make use of cameras, laser sensors, or radar. These sensors are capable of detecting the presence and speed of other vehicles, and that information is used to maintain a safe following distance.

If adaptive cruise control detects an obstruction in the roadway, or the lead vehicle slows down, the system is capable of cutting the throttle, downshifting, and even activating the brakes.

How Do I Use Adaptive Cruise Control?

If you’ve used regular cruise control, then you should have a pretty good idea of how to use adaptive cruise control. In fact, some vehicles with adaptive cruise control provide you with the option to operate in a standard cruise control mode if that's what you're comfortable with.

Specific controls vary depending on the particular vehicle, but the general process involves setting a desired cruising speed and then engaging the cruise control. In cases where a legacy cruise control system is the default mode, you will then have to specifically turn on the adaptive system.

Since adaptive cruise control uses cameras, radar, and laser sensors to monitor the speed and position of the vehicle in front of yours, you are free to focus on maintaining your lane position and checking for other hazards. You still have to remain vigilant, because adaptive cruise control isn't the same as autopilot or a driverless car, but it does take some of the pressure off.

If your vehicle is equipped with a partially adaptive cruise control system, you’ll find that you also have to keep an eye out for traffic jams and other hazards. These partially adaptive systems usually shut down after your vehicle slows down to a certain speed, so they aren’t capable of bringing you to a complete stop. Fully adaptive systems are capable of functioning in stop and go traffic.

Does Adaptive Cruise Control Really Make You Safer?

Adaptive cruise control can help reduce the likelihood and severity of rear-end collisions, but these systems are still relatively limited. Distracted drivers are likely to fail to manually adjust their cruise control settings in time to avoid collisions, so adaptive cruise control can be a huge benefit in those situations.

However, adaptive cruise control can actually cause a reduction in safety if the driver isn’t aware of the limitations of the system.

According to a study performed by AAA, an alarming number of drivers are unaware that their partially adaptive cruise control systems are incapable of completely stopping their vehicles.

Other drivers were unaware that adaptive cruise control doesn’t work properly on winding roads because it can pick up vehicles in other lanes. If you’re fully aware of all those limitations, then adaptive cruise control will make you safer.

What Vehicles Come with Adaptive Cruise Control?

The first vehicle with adaptive cruise control shipped in 1995, but it took a while for the technology to really take off. Most major automakers offer some type of adaptive cruise control, and the few holdouts at least have something on the drawing board. However, the availability of fully adaptive cruise control is somewhat more limited.

BMW was one of the first automakers to offer fully adaptive cruise control, which is a type of cruise control that's capable of bringing a vehicle to a complete stop. That's a big deal, because it allows you to use the system in stop and go traffic. Other types of adaptive cruise control require the driver to take manual control at low speeds.

BMW's fully adaptive cruise control has been available on a variety of models, including 7 series, 5 series, and 6 series, since 2007. Mercedes, Volkswagen, GM, and a handful of others have also rolled out their own fully adaptive cruise control systems.

In a lot of cases, the adaptive cruise control option has been limited to only a few models to start with. A classic example is GM, which initially limited the option to its upmarket Cadillac badge. Then starting with the 2014 model year, a fully adaptive system was also available for the Chevy Impala, and other models received the system after that.

What Types of Adaptive Cruise Control Are Available?

Adaptive and autonomous cruise control systems can be broken down into laser- and radar-based systems, and they can also be differentiated based on the amount of input required from the driver.

Laser-based autonomous cruise control systems use a front-mounted laser to track the position and speed of other vehicles. Due to the limitations of using a laser, these systems often have trouble detecting vehicles are are dirty or otherwise non-reflective, and bad weather can also adversely affect the ability of a laser-based system to track other vehicles.

Radar-based systems are sometimes called radar cruise control, and they use one or more radar sensors instead of a laser. These typically work in a wider range of weather conditions and are typically capable of tracking other vehicles regardless of reflectivity.

Some adaptive cruise control systems are also integrated with precrash technologies, like adaptive braking, and other ADAS like lane departure warning systems.

What Happens When Adaptive Cruise Control Fails?

A potential failure is the main reason that you need to remain vigilant. If your system fails while it’s in use, you will have to manually adjust your speed. The vehicle will still be safe to drive, but you won’t be able to rely on the adaptive system to automatically maintain your following distance.

It’s also vital to understand that some systems can fail even if they appear to be working fine. If your adaptive cruise control uses a laser sensor, then you need to be aware of the fact that it may fail to properly track other vehicles in adverse weather.

Laser sensors can also fail to track vehicles if they’re especially dirty or use non-reflective paint. Radar-based adaptive cruise control is typically capable of tracking vehicles regardless of paint or weather conditions, but none of these systems are infallible.

Where is Adaptive Cruise Control Going in the Future?

Today, adaptive cruise control systems are capable of functioning without any outside input. They simply use a sensor to detect the position and speed of other vehicles and make the necessary adjustments. This technology is also an instrumental component of self-driving cars.

In the future, we could see cooperative adaptive cruise control systems that utilize information from other vehicles and transmit information to other vehicles. An implementation of this type of system would involve one vehicle transmitting speed data to the vehicle behind it, which would in turn transmit speed data to the vehicle behind it, and so on.

The benefit of this kind of advanced adaptive cruise control is that it would not rely on external measurements and sensors that can fail in some situations like current systems.

However, the implementation of this type of system would require a tremendous amount of cooperation between automakers and lawmakers and wouldn't work without an across the board adoption of the technology.