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.

Consumer Use

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 55mph, if the car while traveling that speed catches up to another vehicle going only 45mph, 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 55mph.

Pricing

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 to $2500, depending on the type of ACC, as well as the model of the car.

History

Types

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. A more recent development is the binocular computer vision system, such as that introduced to the US market in model year 2013 by Subaru. These systems have front-facing video cameras mounted on either side of the rearview mirror and use digital processing to extract depth information from the parallax between the two cameras' views. Due to the fact that there are video cameras, this type of ACC is able to reliably determine shape and classification of objects in front of the vehicle, and are also able to specifically detect when a vehicle in front is braking. As of now, this type of ACC is more widely used for lane centering.

[Intelligent Cruise Control (ICC)

SteeringSwitch (ProPilot) Nissan Serena | upload.wikimedia.org/wikipedia/commons/e/e3/SERENA///e-POWER///SteeringSwitch///ProPilot.png]

Assisting systems

Radar-based ACC is often sold together with a precrash system, which warns the driver and/or provides brake support if there is a high risk of a collision. Also in certain cars, it is incorporated with a lane maintaining system which provides a power steering assist to reduce steering input burden on corners when the cruise control system is activated.

Multi-sensor systems

Systems with multiple sensors can practice sensor fusion to integrate the data to improve safety and/or driving experience. GPS data can inform the system of geographic features such as a freeway offramp. A camera system could notice driver behavior such as brake lights and/or a turn signal. This could allow the following car to interpret a turn signal by an exit as not requiring the following car to slow down, as the leading car will exit. Multi-sensor systems could also take note of traffic signs/signals and not, e.g., violate a red light while following a vehicle that crossed before the signal changed.

Predictive systems

Predictive systems modify vehicle speed based on predictions of other vehicles' behavior. Such systems can make earlier, more moderate adjustments to the predicted behavior, improving safety and passenger comfort. One example is to predict the likelihood of a vehicle in a neighboring lane moving in front of the controlled vehicle. One system predicts a lane change up to five seconds before it occurs.

Regulations and norms

Adaptive cruise control is regulated by European norm ISO 15622 Intelligent transport systems—Adaptive cruise control systems—Performance requirements and test procedures. According to this standard, an ACC is partial automation of longitudinal vehicle control to reduce the workload of the driver on roads where non-motorized vehicles and pedestrians are prohibited. It does not deal with stationary objects. According to this standard, ACC includes two classes of systems: the FSRA (full speed range) and the LSRA (limited speed range).

Vehicle models supporting adaptive cruise control

The three main categories of ACC are:

Mercedes Distronic Plus

In 1999, Mercedes introduced Distronic, the first radar-assisted adaptive system, on the Mercedes-Benz S-Class (W220) and the CL-Class. Distronic adjusts the vehicle speed automatically to the car in front in order to always maintain a safe distance to other cars on the road. In 2005, Mercedes refined the system ("Distronic Plus") making the Mercedes-Benz S-Class (W221) the first car to receive the upgraded system. Distronic Plus could now completely halt the car if necessary on most sedans. In an episode of Top Gear, Jeremy Clarkson demonstrated the effectiveness of the system by coming to a complete halt from motorway speeds to a round-about and getting out, without touching the pedals. In 2016, Mercedes introduced Active Brake Assist 4, the first emergency braking assistant with pedestrian recognition. One crash caused by Distronic Plus dates to 2005, when German news magazine "Stern" was testing Mercedes' original Distronic system. During the test, the system did not always manage to brake in time. Ulrich Mellinghoff, then Head of Safety, NVH, and Testing at the Mercedes-Benz Technology Centre, stated that some tests failed because the vehicle was tested in a metallic hall, which caused problems with radar. Later iterations received an upgraded radar and other sensors, which are not disrupted by a metallic environment. In 2008, Mercedes conducted a study comparing the crash rates of Distronic Plus vehicles and vehicles without it, and concluded that those equipped with Distronic Plus have an around 20% lower crash rate.

Aftermarket