Car tech: Taking drivers' helpers for a spin

Think your spouse is a back-seat driver? Check out some of these automated features.

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An upcoming model -- the Mercedes GL450 -- will also steer you back into the lane with a slight nudge. In the future, this autonomous control will go even further. Research at Stanford University for the DARPA Challenge suggests that auto makers will morph LDW to allow a vehicle to drive without human interaction for long stretches of the highway by using adaptive cruise control and lane-keeping to keep the car going.

Adaptive cruise control

Adaptive cruise control adjusts the speed of the vehicle automatically, according to a pre-set condition (such as 1.5 seconds or 3 seconds) between you and the car ahead. The Lexus LS-430 first introduced this feature in 2000 and called it the Dynamic Laser Cruise Control System. High-end Cadillac and Mercedes models have had this ability for some time, too.

Interestingly, while this feature seems complex, it relies mostly on a Doppler radar system (usually in the front grill) that scans for reflections. In some models, there is a second video camera mounted above the windshield.

Adaptive cruise is one of the most robotic features in cars such as the Mercedes E350. During my test drive, the E350 slowed down gradually, easing me back from a slow-moving vehicle several hundred feet ahead. The technology, called Distronic Plus, lets you configure when the car starts slowing based on distance to the vehicle ahead.

"Currently, the models we offer today work at highway speed but we are quickly moving towards vehicles that work at stop-and-go speeds, slowing you down for a construction zone or traffic jam," says Capp. "What the system is doing is using a radar that's picking up reflections and using them with Doppler radar technology. We calculate velocity and distance, and process the image to keep the space between you and the vehicles in front of you."

Adaptive cruise control
This indicator on an Acura ZDX displays an icon that adaptive cruise control is enabled. Adaptive cruise uses radars -- not unlike those used for tracking thunderstorms -- looking for objects' reflections.

"These systems have sweet spots in terms of the distance an object can be detected and at what cruising speeds," adds Rob O'Reilly, a director of testing and measurement at Analog Devices, a company that makes the sensors and computer modules for autonomous controls. The systems run when the car is doing speeds from about 15MPH to 115MPH, and they can spot other vehicles that are up to 492 feet away. "Out of a handful of actual applications, most run in the 60GHz to 80GHz range" to measure the distance between cars, he says. The sensor outputs, in turn, are handed to the main computer -- usually located under the dash -- with the automatic steering module, brake assembly module and acceleration module located closer to the engine.

Another vehicle, the Volvo XC60, uses a new technology called City Safety that works on city streets. "If a driver is going less than 10 miles an hour in freeway traffic, the car will brake at full force, preventing you from hitting the car in front of you," says Mike Caudill, an auto expert at NADA Guides, the used-car guides published by the National Automobile Dealers Association. Caudill explains that adaptive cruise at slow speeds would help mitigate fender-benders.

On GM models such as the Cadillac STS, adaptive cruise helps improve gas mileage on long commutes because the computer controls gradual acceleration and smoothes braking. Traditional (standard) cruise control requires "the driver to be on and off the brakes, thus turning the system on and off. Whenever you hit the brakes, it disengages the cruise control," Caudill explains. "Adaptive Cruise Control allows the car to coast without hitting the brakes. Hitting the brakes forces the car to accelerate more quickly up to the previously set speed. Adaptive will maintain whatever the speed of the car in front of you is . . . and at the distance set by the driver. This helps you save on fuel."

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