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Car Tech: What is Adaptive Cruise Control?

Set it and forget it, that describes how you use adaptive cruise control today. It’s like traditional cruise control but smarter. It can “see” cars ahead and automatically adjust your vehicle’s speed, even coming to a complete stop, in some cases.

  • Adaptive Cruise Control is a Level 1 Autonomous driving aid that maintains either a set speed or follows a slower vehicle at a user-specified distance.
  • Not all Adaptive Cruise Control systems work the same, understanding the differences is important when choosing a vehicle.
  • Although convenient, these systems still require the driver to maintain focus in case of emergency situations.

Like with a standard cruise control system, a driver chooses a specific speed for the adaptive cruise control system to maintain. Additionally, adaptive cruise control automatically adjusts vehicle speed to maintain a safe distance from traffic ahead. Drivers decide whether that following distance is closer or farther, depending on personal preference. Most have a button that lets the driver increase or decrease that gap.

According to the Society of Automotive Engineers (SAE) International, adaptive cruise control is a Level 1 autonomous driving system. When combined with an active lane-keeping assist system, it graduates to a Level 2 autonomous system. Even at Level 2, however, it requires attention from an alert and vigilant driver.

How Does Adaptive Cruise Control Work?

Adaptive cruise control uses laser sensors, radar sensors, cameras, or some combination in order to identify vehicles ahead and to determine the distance between your car and the other vehicles. In turn, that information is sent to the braking and acceleration systems helping your car automatically keep a safe following distance.

Laser-based adaptive cruise control requires that vehicles ahead have a reflective surface. Therefore, it might not sense a matte-finish car or a dirty car on the road ahead. To work properly, the laser sensor must be exposed, which creates unsightly design problems. Toyota used laser adaptive cruise control in the 2000s but has since switched to radar-based systems.

Radar-based adaptive cruise control is popular because automakers can hide the sensors behind plastic body panels or the front grille, improving vehicle styling. Systems with multiple sensors can gather more data and typically work with greater accuracy and refinement. Most modern vehicles use radar-based adaptive cruise control.

Camera-based adaptive cruise control typically uses dual cameras. Software processes the images to determine the distance to vehicles ahead and to adjust vehicle speed accordingly. Subaru’s EyeSight technology is the best-known example of this type of adaptive cruise control.

Know What The System Does Before Driving

Adaptive cruise control in action

Adaptive cruise control systems do not work the same way. It is important to know how yours works before using it:

  • Some systems work within a limited vehicle speed range
  • Some are full-speed-range systems that bring your vehicle to a full stop
  • Some include stop-and-go capability, either automatically resuming speed when traffic starts to move again or doing so with a prompt from the driver, such as tapping the accelerator pedal or pushing the Resume button on the steering wheel
  • Some try to predict required braking situations by looking one vehicle ahead
  • Some vehicles offer both standard cruise control and adaptive cruise control because some people don’t like the adaptive systems

Remember that adaptive cruise control cannot always stop your vehicle if you’re approaching stopped or very slow traffic at speed. If you’re going 70 mph, come over a hill, and stopped cars are ahead, you’d better be ready to jam your foot on the brake pedal and possibly swerve to avoid an accident. Although many of the automated cruise control systems are paired with forward collision avoidance systems, no software can overcome physics. If you're speeding and there's a sudden stop, you as the driver will have to intervene.

Know, too, that weather conditions can adversely impact adaptive cruise control operation. Snow, bright sunlight, dark shadows, heavy rain, and fog can cause the adaptive cruise control to stop working.

Studies show that adaptive cruise control systems (and automatic emergency braking systems) are effective at reducing collisions with vehicles ahead. So go ahead: set it and forget it. Just remember that you need to be ready to take control at any time.

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