Frankfurt Auto ShowFRANKFURT – The ’06 Mercedes-Benz S-Class luxury sedan will offer a next-generation adaptive cruise control (ACC) system that can bring the vehicle to a complete stop, then resume a safe speed based on the distance from the vehicle ahead.

ACC has been appearing on a limited number of luxury cars in Europe and the U.S., although the feature has been more popular in Europe.

It generally uses radar sensing to monitor the speed of the vehicle ahead. When the lead vehicle speeds up or brakes, so does the ACC vehicle.

But until now the feature only has been able to slow an ACC-equipped vehicle to about 20-30 mph (32-48 km/h), at which point a light flashes, the system is deactivated and the driver must actively manipulate the brake pedal to stop the car completely.

Continental supplies long-range radar sensor for Mercedes' current Distronic adaptive cruise control (pictured).

Mercedes officials say the new S-Class is the first production vehicle to employ this next-generation ACC, although other auto makers appear close to adopting the system. Mercedes developed the device in concert with Germany’s Continental Automotive Systems, which supplies the necessary radar sensors.

Mercedes will market the system as “Distronic Plus” as a way to promote stress-free, safe driving. The auto maker highlighted the stop-and-go capability on the new S-Class at the vehicle’s premier here at the Frankfurt auto show.

The system will be optional on the S-Class at launch in Europe at the end of September and in the U.S. in January, says Christian Frueh, Mercedes’ director of passenger car engineering-brakes and driver-assistance systems. Mercedes says it now is in the process of gaining regulatory approval to sell the device in Asia.

The auto maker has ambitious projections for take rates of about 40% worldwide for the new Distronic Plus system on the S-Class, Frueh says. That compares with about 10%-12% for the less-advanced ACC system on the current S-Class.

Short-range radar sensors for Distronic Plus hidden behind S-Class bumper fascia.

Frueh, who led development of the new Distronic Plus, says the 40% projection stems from consumer reaction and dealer interest in the new technology.

The optional price for the new feature will be about E2,300 ($2,830), compared with E2,000 ($2,450) for the current version, Frueh says.

Continental has supplied Mercedes vehicles with ACC since 1999, when it debuted on the current S-Class. The system now also is available on the E-Class.

Until now, Continental has supplied Mercedes with a 77-gigahertz long-range radar sensor for ACC that worked only at higher speeds.

For the new generation, with stop-and-go, Continental also provides two 24-gigahertz radar sensors with short-range capability, allowing ACC to function at any speed. On the S-Class, the short-range sensors are embedded behind the front bumper fascia, and the long-range sensor rests behind the grille; none is visible.

When the vehicle comes to a complete stop, based on a braking event for the lead vehicle or based on sudden detection of an object in front of the car, the S-Class will not re-launch until the driver reactivates the system by pressing the accelerator or a lever attached to the steering column, Frueh says.

The sensors recognize changes in distance to the vehicle ahead much faster than the driver, and Continental says in most cases the system will apply the brakes sooner than the driver, helping prevent collisions. The new system also applies more brake force than the old system.

Currently, Continental uses radar sensors for ACC but says it also is developing systems based on infrared technology.

Continental is not alone in the ACC market.

Robert Bosch GmbH supplies ACC for the BMW 7- and 5-Series; TRW Automotive supplies the technology for the Volkswagen Phaeton and all-new Passat; and Delphi Corp. produces ACC for the Cadillac XLR roadster.

All three competitors say they will launch stop-and-go ACC programs for production vehicles - mostly in Europe - in 2006.

In addition, Siemens VDO Automotive will join the segment with its first ACC production contract in 2007 for a European auto maker. In mid-2008, the system will be capable of stop-and-go functionality. The Siemens VDO system will employ "lidar," integrating laser and radar technology.

With its stop-and-go capability, Continental sees the new S-Class as embracing the supplier’s Active Passive Integration Approach (APIA), an attempt to prevent accidents by combining advanced active safety technology such as ACC and electronic stability control (ESC) with passive devices such as seatbelts and airbags.

In addition to ACC, Continental supplies the new S-Class with its latest-generation ESC stability control system that employs four additional pressure sensors to help prevent a vehicle from skidding out of control. Brake assist also provides additional stopping force in emergencies and is designed to shorten stopping distances.

Also for the S-Class, Continental delivers a brake booster with tandem master cylinder, which offers increased protection against leg injuries.

In frontal collisions, a torque damper rotates and retracts the entire booster actuation unit, minimizing the risk of injury for the driver.