Adaptive cruise control

Adaptive cruise control (ACC) is a type of advanced driver-assistance system for road vehicles that automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. As of 2019, it is also called by 20 unique names that describe that basic functionality. This is also known as Dynamic cruise control.

Control is based on sensor information from on-board sensors. Such systems may use a radar, laser sensor or a camera setup allowing the vehicle to brake when it detects the car is approaching another vehicle ahead, then accelerate when traffic allows it to.

ACC technology is regarded as a key component of future generations of intelligent cars. The technology enhances passenger safety and convenience as well as increasing road capacity by maintaining optimal separation between vehicles and reducing driver errors. Vehicles with autonomous cruise control are considered a Level 1 autonomous car, as defined by SAE International. When combined with another driver assist feature such as lane centering, the vehicle is considered a Level 2 autonomous car.

Adaptive cruise control does not provide full autonomy: the system only provides some help to the driver, but does not drive the car by itself. For example, the driver is able to set the cruise control to 55 mph, if the car while traveling that speed catches up to another vehicle going only 45 mph, the ACC will cause the car to automatically brake and maintain a safe distance behind the vehicle in front, and will maintain that distance until the road opens up again and the car can safely return to the initially set speed of 55 mph.

Given the fact that ACC is considered a key component of future generations of intelligent cars, and the fact that it can increase comfort and safety on longer drives, ACC systems cost anywhere between $500 and $2500, depending on the type of ACC, as well as the model of the car.

Laser-based systems work using LIDAR (Light detection and ranging), allowing laser-based ACC to provide the largest detection distance as well as the best accuracy of all ACC systems. However, laser-based systems do not detect and track vehicles as reliably in adverse weather conditions due to the fact that fog, or water particles in the air may absorb and or redirect the light emitted from the laser, through absorption, scattering, and reflection. Laser based ACC systems also have a more difficult time tracking dirty (and therefore non-reflective) vehicles. Laser-based sensors must be exposed, the sensor (a fairly large black box) is typically found in the lower grille, offset to one side.

Radar-based sensors work by emitting a radio wave at a frequency of either 24GHz or 77GHz. As these signals are emitted, the car computes how long it takes for the signal to return, thus finding out how far away a vehicle may be in front of it. Due to the widely distributed beam, radar ACC systems allow for a much wider field of view while still being able to provide accurate measurements of 160+ meters (Roughly 525 feet). These radar systems can be hidden behind plastic fascias; however, the fascias may look different from a vehicle without the feature. For example, Mercedes-Benz packages the radar behind the upper grille in the center and behind a solid plastic panel that has painted slats to simulate the look of the rest of the grille.

Single radar systems are the most common. Systems involving multiple sensors use either two similar hardware sensors like the 2010 Audi A8 or the 2010 Volkswagen Touareg, or one central long range radar coupled with two short radar sensors placed on the corners of the vehicle like the BMW 5 and 6 series.