Bill Howard

People used to know their place in the world: centered between the striped and solid pavement markings, 2 seconds of drive-time behind the car in front, and when parking, not jammed against the bumper of the car parallel-parked behind them. Today, sensors, cameras, and microprocessors let the driver – correction: the well-heeled driver – keep his car properly positioned, even when he's not fully alert.

Just a word of warning: The cocoon of technology is not a silent partner. Warning beeps remind passengers, as well as you, of driving faux pas. (That's on top of the beeps emanating from your cell phone, BlackBerry, radar detector, and so on.) Here are three technologies I've spent time with recently: active cruise control, lane departure warning, and backup sonar and camera. All help. Most beep.

Active (or Whatever) Cruise Control (ACC)

Most of today's cars have cruise control. Set it to 75 on the interstate, and you can cruise effortlessly – until you come upon some dolt doing 55 in the left lane. (Q: On superhighways, what do American and British drivers have in common? A: Both drive to the left.) Enter active cruise control (also called adaptive, automatic, or intelligent cruise control). Radar or laser sensors look for traffic in the lane in front of you, slow you to a safe following distance, apply the brakes if necessary, and then bring you back up to speed once the obstacle has changed lanes. Most ACC systems can bring you down to 20 miles per hour; then there's a warning beep, indicating, "You're on your own, lad." More than a dozen automakers offer ACC; the cost ranges from $600 to $3,000. (If you want fully automatic stopping, that's coming in 2006. Long- and short-range radar sensors, sometimes aided by a camera, see that you're about to nail a car or a pedestrian and apply just-in-time braking force. Some do it only when you're on the brakes; others will start without you.)

An icon in the dash lights up to indicate you're in range of another car and have radar lock. Most of the time, ACC works wonderfully if you close too quickly, or the car ahead slows, or another driver cuts in front of you (as punishment for leaving a safe following distance). When the distance gets too close for the black box' comfort, your car backs off the throttle and then applies the brakes. You get to set the spacing to roughly one, two, or three seconds of following distance.

But ACC doesn't deal well with dense traffic and let me down on the trip I like least: returning to the New York area at the end of a holiday weekend, when traffic the last 100 miles can vary from 65 mph to a crawl and then back up again. ACC handles deceleration well most of the time and re-acceleration sometimes. There were a couple times when I chickened out and went for the brakes rather than let ACC prove it could handle sudden braking by the car in front. When traffic flow drops below 20 mph, you have to accelerate past 30 mph and re-engage ACC. Work, work, work. At the closest distance, aggressive drivers still have room to cut in front. And ACC doesn't function at speeds above 90 mph, in part because the radar sees ahead a couple hundred yards, not a half mile, and you might close too quickly. Something to remember on the Autobahn.

ACC is fairly polite: It doesn't complain about your driving in front of the passengers, deceleration is gentle, and the only beeps are when it cuts out. Continued...