The sportiest premium sedan in the full-size class – the new Audi A8
The new Audi A8 L offers a broad portfolio of optional assistance systems that make driving even more relaxing and composed. The large sedan’s electrical system includes seven bus systems and, depending on the equipment, roughly 100 control units. The particularly high-performance FlexRay bus system networks many driver assistance and suspension control units. It provides for fast and reliable data transfer between the controllers.
High-performance: adaptive cruise control with stop&go function
The central driver assistance system in the new Audi A8 is the adaptive cruise control (ACC) with stop&go function and Audi pre sense front (not available in the A8 hybrid). The radar cruise control system regulates the speed and the distance to the vehicle ahead by accelerating and braking in a speed range from 0 to 250 km/h (155.34 mph), and brakes automatically within certain limits. The driver uses the MMI operating system to determine how comfortable or sporty travel should be – four levels and four distance stages are available.
ACC stop&go analyzes the data from up to 27 other systems on board the A8. The most important information of all is provided by its two radar sensors. Located in the lower part of the front end, they operate in the frequency range between 76 and 77 GHz and cover an area approx. 250 meters (820.21 ft) in length with an angle of aperture of 40 degrees. A video camera mounted on the rearview mirror looks some 60 meters (197 ft) ahead, also with an aperture angle of 40 degrees.
The system uses this large amount of information to support the driver proactively. For example, it can use the predictive route data provided by the optional MMI navigation plus to reliably calculate the proper line on the highway even in bends. Whether the driver is turning, changing lanes, passing another vehicle or driving on a winding rural road: ACC stop&go handles such situations with ease.
The active range of ACC stop&go also includes rolling at low speed. In a traffic jam, for instance, the system slows the new A8 to a complete stop. If the stop is brief, the sedan automatically resumes moving again; after a longer stop the driver must lightly touch the accelerator or tap the cruise control lever. The system also uses the signals supplied by the ultrasound sensors of the Audi parking system located in the front bumper when automatically starting off again.
Complex safety system: Audi pre sense
The Audi pre sense safety system is available in a number of different versions in the new A8. In the standard version, Audi pre sense basic, it intervenes upon detecting an unstable driving situation via the sensors of the ESC electronic stabilization control system. In this case, Audi pre sense makes sure that the front seat belts are tensioned by small electric motors and that the sunroof and the windows are closed down to a small gap. The hazard lights warn the traffic behind.
Audi pre sense front is available in combination with ACC stop&go. Above 30 km/h (18.64 mph), it helps the driver avoid imminent accidents or at least mitigate any damage. Audi braking guard is activated in critical situations. It first warns the driver via acoustic and visual signals. It prefills the brake system at the same time and also tautens the pneumatic springs and dampers.
If the driver still does not react, then the system briefly brakes the vehicle – a jolt which serves as the second warning. The seat belts are slightly tensioned at the same time. If the driver depresses the pedal now, the hydraulic brake assist increases braking power as appropriate for the situation. Should the driver ignore the warning jolt, autonomous partial braking occurs, which decelerates the A8 at 3 m/s2. This assumes that the preceding vehicle is moving. Windows and the sunroof are closed, the hazard warning lights are activated and the seat belts are tensioned strongly.
Yet another Audi pre sense subfunction, Audi pre sense rear, is coupled with Audi side assist. If the system detects an imminent rear-end collision, it uses the adaptive brake light to warn the traffic behind. If the situation becomes critical, it closes the windows and sunroof and tensions the seat belts. Depending on the configuration installed, the seats may also become active. The top of the back rest and the front head restraints move forward and upward; the side bolsters are filled with air.
If the A8 is equipped with the full version of Audi pre sense – the assistance package including Audi pre sense plus – a third and a fourth stage then follow in the event of an emergency. The system now increases deceleration to 5 m/s² and tightens the belts completely. The last braking phase – the autonomous full brake application – occurs roughly half a second before an inevitable collision. The collision and its consequences are greatly mitigated, for by the time the impact occurs the sedan can reduce its speed by as much as 40 km/h (24.85 mph).
At speeds below 30 km/h (18.64 mph), the new Audi A8 brakes autonomously with full force in an emergency – regardless of whether the car in front is driving or standing still. Below 20 km/h (12.43 mph), this full braking in many cases prevents the accident altogether. In other cases, it greatly reduces the impact speed, thus reducing the severity of the accident.
Another innovative system becomes active in the event of a collision. The secondary collision brake assist applies the brakes again without any action on the part of the driver to prevent the A8 from rolling further in an uncontrolled manner.
Radar has your back covered: Audi side assist
The lane change assistant Audi side assist is active at speeds of 30 km/h (18.64 mph) and above. Two radar sensors at the rear of the sedan monitor events to a distance of around 70 meters (229.66 ft). If they consider a detected vehicle to be critical to a lane change because it is in the blind spot or approaching quickly, a yellow LED indicator lights up in the exterior mirror housing.
If the driver nevertheless activates the turn signal to change lanes, the LED lights flashes brightly multiple times – a signal that can hardly be overlooked. The visual signal is designed so that in practice it is only visible to the driver. Its brightness varies with the ambient light and can be adjusted via the MMI operating system as well as deactivated via a button in the A-pillar.
Stay between the lines: Audi active lane assist
Audi active lane assist warns the driver if he or she is about to leave the lane inadvertently. The system is active at speeds of 65 km/h (40.39 mph) and above. A camera in front of the interior mirror monitors the road to a distance of 60 meters (196.85 ft) and with an angle or roughly 40 degrees. Software processes its images and detects the lane markings and the course the new A8 is following between them.
If the sedan approaches a line without the turn signal being activated, the system helps the driver to steer back into the lane by subtly intervening in the electromechanical steering. The driver uses the MMI to determine how soon the intervention should occur and whether it should be accompanied by a steering wheel vibration and a warning tone. If the driver selects early intervention, the system helps to keep the A8 in the center of the lane.
Audi active lane assist also intervenes if the car is in danger of skidding. It supports proper countersteering by briefly boosting or reducing the degree of power assistance. Together with Audi side assist, the system is also activated in the event of an impending collision with a vehicle in a parallel lane.
Always informed: Camera-based speed limit display
The camera-based speed limit display can detect speed limits and relevant additional signs. It presents them as graphics on the display of the driver information system or on the optional head-up display. The system analyzes the images delivered by the video camera on the interior mirror and compares them against the information from the MMI navigation plus.
Long-range vision in the dark: The night vision assistant
Another high-end system in the new Audi A8 is the night vision assistant, which detects and highlights pedestrians and larger wild animals. Its far infrared (FIR) camera located in the Singleframe grille detects heat emitted by objects. A computer converts the information from the camera into black and white images and shows them on the driver information system’s seven-inch display.
While the cooler surroundings appear dark, people and larger wild animals appear strikingly bright. The image-processing software detects them up to 130 meters (426.51 ft) away and highlights them with yellow markings on the display.
If the computer detects a hazardous situation, the object is marked red and a warning gong sounds. A warning also appears in the optional head-up display. In addition, the LED or Matrix LED headlights flash briefly three times to illuminate the object (if it is a person). The brake system is prefilled at the same time.
With its 24 degree horizontal angle of aperture (vertical angle 18 degrees), the far infrared camera can look ahead up to 300 meters (984.25 ft), far beyond the high beam range. A protective window prevents stones from damaging the camera, which is heated in cold weather and, if dirty, cleaned together with the headlights.
Convenient: Park assist systems
Audi offers a number of park assist systems in the new A8. The parking system plus (standard in the S8 and A8 L W12) uses eight ultrasonic sensors to indicate the distance to the front and rear acoustically and graphically. This can be complemented with the optional reversing camera and 360° cameras. Four small cameras record the car’s immediate surroundings and generate a virtual top-down view. The driver can call up various other camera angles on the MMI monitor.
New in the Audi A8 is the park assist with 360° display. It uses 12 ultrasonic sensors to locate and measure parking spaces along a road when the vehicle is being driven at a moderate speed. As soon as the system finds a large enough space, a corresponding notification appears on the driver information system display. Once the driver puts the car in reverse, the system takes over the work of steering – the driver only has to accelerate, change gears and brake. The 360° display warns the driver of any obstacles to the side of the vehicle.
Parking spots can be either parallel or perpendicular to the road. The system will maneuver forward and backward multiple times while parking, if necessary. It provides similar support when pulling out of parallel parking spaces. During this process, the vehicle moves no faster than seven km/h (4.35 mph).