ANN ARBOR, Mich. (AP) — In a few weeks, about 2,800 cars, trucks and buses will start talking to each other on the streets of Ann Arbor, Mich., in a giant experiment that government officials are hoping will lead to safer roads.

Wireless devices will allow the vehicles to send signals to each other, warning their drivers of potential dangers such as stopped traffic or cars that might be blowing through a red light. They can even get traffic lights to turn green if no cars are coming the other way.

The U.S. Department of Transportation and the University of Michigan are hoping the year-long, $25 million project generates data that show the devices can cut down on traffic crashes. Officials say eventually this could lead to the devices going in every car. About 500 vehicles with the devices are now on the roads. That will rise to 2,800 in about six weeks, officials said Tuesday.

"This is a big day for safety," Transportation Secretary Ray LaHood said at an event at the university formally kicking off the experiment. "We'll use this information to decide if vehicle technology can be applied to daily lives."

More than 32,000 people died last year in U.S. traffic crashes, down 1.7 percent from 2010. The number of crashes has fallen in recent years as automakers added safety devices such as air bags, antilock brakes and stability control, which helps drivers keep cars under control in emergency situations.

But LaHood said Tuesday that 80 percent of crashes in which the drivers aren't impaired by drugs or alcohol could be prevented — or the severity reduced — if cars could talk to each other.

When the technology will make its way into cars and trucks everywhere is unclear. The National Highway Traffic Safety Administration has the authority to order the devices placed in all new cars, but LaHood said they'll have to study the data before making any decision. The data will be available in about a year.

In a demonstration at the Transportation Research Institute, a Volkswagen GTI equipped with a device got a signal that a car up ahead of it had braked. The warning allowed the GTI driver to slow down before seeing the brake lights on the car in front of him. The device also warned the GTI driver at a stop sign that another car was about to speed through the intersection.

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Ford, General Motors, Honda, Hyundai/Kia, Mercedes-Benz, Nissan, Toyota and Volkswagen/Audi all are supplying vehicles and taking part in the test.

Peter Sweatman, director of the institute, said testers will look for data showing that the warnings prevented crashes. Previous tests, on a smaller scale, showed the devices can stop crashes, he said.

Technology is available so that connected cars could be on the road nationwide in under 10 years, Sweatman said.

"I think this is going to kick everything off," he said. "This is going to move everything forward."

Automakers have been adding safety devices such blind-spot warning detectors that warn a driver if there's a car in an adjoining lane, and radar-activated cruise control that can slow cars down if they're approaching an object too fast. The experiment should help tie them together, officials said.

In February, Ford Executive Chairman Bill Ford called for just that in a speech to a mobile electronic device conference in Barcelona, Spain. He said the mobile device industry should join with automakers and governments to develop connected car technology to solve looming congestion and safety problems around the world.