THE EXPERIMENT: Wireless devices will allow about 2,800 cars, trucks and buses in Ann Arbor, Mich., to talk to each other. The year-long experiment on real streets will let officials gather data to find out if the devices will make roads safer.

HOW IT WORKS: Volunteers' cars will be equipped with devices that transmit signals to other cars, warning drivers that cars in front of them are slowing or that a car might be about to blow through a stop sign or traffic light. The transmitters have a range of about 700 to 1,000 feet.

WHAT WILL HAPPEN: The U.S. Department of Transportation and the University of Michigan will collect data to see if the devices prevent crashes. The data could be used to justify placing the devices in all new cars, but that's several years away.