Washington ? The scene is familiar to anyone who has navigated a supermarket parking lot: A man gets into his car to leave and an absent-minded shopper abandons a cart behind him. The driver begins backing up.

There’s no crunch. In this DaimlerChrysler video, the car stops an inch from the cart  even though the driver never applied the brakes.

An onboard computer did it for him, with help from a radar system mounted on the bumper.

Automakers are working on systems that send out pulses to determine the location, size and distance of objects and then reflect that information back to sensors on the front and rear bumpers.

Applications could extend well beyond supermarket parking lots.

The sensors might detect a child running behind a minivan backing out of a driveway. Or they might measure the speed and angle of a drunken driver swerving into oncoming traffic. The onboard computer could tighten the seat belt and deploy the air bag just before impact to lessen the chance of serious injury.

“Through sensors, vehicles sharing the road in the more distant future would be able to speak to each other,” said Ford Motor Co. spokeswoman Sara Tatchio. “The possibilities are amazing.”

Ultra-wideband technology sends millions of narrow pulses each second over the airwaves to get a precise reading of an object’s location and distance. It can carry huge amounts of data over a short distance and has the ability to carry signals through objects that reflect signals at more limited bandwidths.

It has myriad potential uses, from allowing a home computer to network with other appliances to detecting objects behind a wall, buried underground or even inside a person.

DaimlerChrysler, BMW, Volkswagen, Jaguar, Renault, Audi, Ford and Volvo all lobbied the Federal Communications Commission to allow them to use ultra-wideband in vehicles. The FCC agreed last month.

Automakers, anticipating approval, have been secretive about their work for competitive reasons but some are far enough along with development that consumers could see the technology in new vehicles within a couple of years.

“It’s going to allow us to move forward with a system that will help avoid collisions and will detect pedestrians and other objects or other hazards,” Dennis Fitzgibbons, director of public policy for DaimlerChrysler, said of the FCC decision. “These are things we hope to make available as quick as we possibly can.”

Some vehicles already use radar to detect objects in their path, but the measurements are less precise and are not integrated with the vehicle’s braking or restraint systems. The systems simply warn the driver that an object is approaching, either with beeps or a dashboard light.

Russ Rader, spokesman for the Insurance Institute for Highway Safety, is skeptical that ultra-wideband will dramatically improve vehicle safety.

“They may perform great on the test track, but they often fall flat on a real highway,” he said.