To declare cruise control as a ubiquitous feature on cars today is no understatement.

Ward's data indicates 86% of new cars and 87% of new light trucks sold in the U.S. last year incorporated the simple mechanism that locks a vehicle into a desired speed on long hauls, whether uphill or down. That's up from 35% in 1977.

But like most mechatronic automotive technology, this rudimentary device is evolving and becoming much more intelligent, and the next generation takes cruise control well beyond commodity status.

Adaptive cruise control (ACC) employs a laser or radar sensor — embedded behind the grille — to detect moving vehicles in the lane ahead. The sensor works in tandem with the throttle and brakes and allows a vehicle to maintain a comfortable following distance from the car ahead. If the lead vehicle suddenly brakes, so does the ACC car. And if another driver changes lanes and disturbs the field of vision, the ACC vehicle brakes and readjusts to the speed of the new lead vehicle. If the lane is clear, the system will assume the driver's chosen speed.

For now, the feature is limited to luxury vehicles, including the Audi A8 and A6, Cadillac XLR, Volkswagen Phaeton, Lexus LS 430 and RX 330, five Mercedes-Benz models, BMW 7-Series, 6-Series and 5-Series and Jaguar XK and XJ. The cost is not insignificant. BMW offers ACC as a $2,200 option.

Today, ACC is moving slightly down-market. Toyota Motor Corp. offers Dynamic Laser Cruise Control (supplied by Denso Corp.) as standard equipment on the '05 Sienna XLE Limited minivan, which carries a sticker price of $37,495.

“We wanted the Sienna XLE Limited to be a very high-class vehicle that people could drive comfortably,” says Andy Lund, Toyota's Sienna program manager-development and planning operations.

Lund considers minivans a perfect market for ACC because they often are used for long trips. Rather than constantly adjusting traditional cruise control based on traffic, ACC does it automatically — and will help with fuel economy, too, by enabling simple drafting off the lead vehicle, Lund says.

Whether consumers are ready for this technological leap is open to debate. A team of Ward's editors recently evaluated an ACC-equipped VW Phaeton owned by TRW Automotive, which supplies VW with the technology. In 2003, roughly 30% of Phaetons were equipped with ACC.

For now, only the Phaeton in Europe is available with ACC, but U.S. versions will offer it likely in the first quarter of 2005, VW says. TRW also has another European customer for ACC for a vehicle (higher volume than Phaeton) that launches in spring.

Ward's editors found the technology to be intriguing, capable and relatively easy to use, but very much a work in progress.

“There were times when I felt I could relax, knowing the car would adjust to the changing speeds of the vehicles in front,” writes Alisa Priddle, editor of Ward's Automotive Reports. “But trusting it was no easy feat.”

She describes left-lane highway driving with ACC as a thrill ride. “When an opening occurs in front of you, the car can accelerate a little too quickly for comfort. And when it catches up to the car in front, there is that moment of panic as to whether or not it will brake. You hang on for the ride, with your foot hovering over the brake, just in case. And it's very hard to wait that extra second, trusting the system will respond.”

Exit ramps also were a sore point with editors, as the vehicle will accelerate if a lead vehicle does not exit as well. Without a target vehicle, the ACC car will disconcertingly resume the set speed, sending the vehicle hurtling toward a stop sign or tight curve. The feature takes some getting used to.

On the Phaeton, the TRW radar-based system does a good job of focusing on only the car in the lane ahead, as opposed to a vehicle in an adjacent lane, or one parked beside the road. It does so with sophisticated algorithms that predict where the ACC vehicle is heading. But during Ward's testing, the system occasionally lacked intuition.

“I found in city driving,” Priddle writes, “when a bus in front of me changed lanes, the system continued to recognize an object in front. So there I was, slowed almost to a stop, with nothing in front of me and a confused driver behind wondering what my problem was. I had to override it and step on the accelerator.”

Ward's Editorial Director David Zoia found the braking too abrupt, no matter how much distance he set between the Phaeton and the lead vehicle. “I think it would be better if the braking started earlier and came on more gradually,” he writes. “Earlier braking would help boost the driver's confidence.”

Future generations of ACC may incorporate “stop-and-go” capability, meaning it can initiate a full stop if the car ahead stops as well. But for now, ACC will slow a vehicle to about 25 mph (40 km/h) and then shut off, leaving the rest of the braking, at a stop sign, for instance, to the driver.

Most editors liked the display (on the dashboard, above the steering wheel) and described it as effective, without distracting. “It gives you some confidence the system is working,” Zoia writes. “I also like the lights on the speedometer indicating the speed setting. And the control buttons are well positioned and easy to use.”

The technology is impressive but cannot safeguard against boneheaded maneuvering by fellow motorists.

The Phaeton's ACC system has a radar range of 490 ft. (150 m), and the driver can adjust the distance to the lead vehicle. But no matter how small that gap, an inconsiderate driver can muscle his way between the ACC-equipped car and the lead vehicle, prompting a hard braking event.

Ward's AutoWorld Editor Drew Winter was more trusting and found the system impressive. “Change lanes behind a much slower vehicle, and the system will brake hard,” he says. “The system really works.”

Overall, despite a few problems, Ward's editors liked the technology but don't drive long distances enough to demand the feature on their next new vehicle.

TRW is trying hard to take cost out of the system so it can be offered on less-expensive vehicles. The current-generation device costs an OEM about $500, but the next-generation ACC will be smaller, lighter and more advanced — and cost about half the price, says Jim Cossins, TRW's chief engineer-braking systems.