Cars of the future will know when they're about to get hit — and how to speak up about it.

U.S. auto safety regulators on Monday took the first steps toward mandating that automakers build cars that talk to one another. They would speak in short-range radio signals, trading messages that would prevent accidents on a broad scale, according to the Transportation Department.

The most advanced cars today can already spot trouble ahead. They use sensors to detect cars or fixed objects ahead, and alert drivers — or, in some cases, even slam on the brakes.

The radio system aims to push that concept much further, enabling vehicles to engage in two-way conversations. A stopped car, for instance, could theoretically send a signal to warn another car (and driver) that's speeding in its direction. Cars could also engage in something like group discussions, exchanging facts about speed, direction and traffic conditions as fast as 10 times a second.

"This is just the beginning of a revolution in roadway safety," U.S. Transportation Secretary Anthony Foxx said Monday.

Foxx characterized the decision as a watershed event that could prevent as much as 80% of the more than 30,000 traffic fatalities that occur each year in the U.S.

Making such systems a reality could take many years. The agency's National Highway Traffic Safety Administration will issue the standards and rules for installing such systems before the end of the Obama administration. But it will be up to automakers to build the communications systems, GPS sensors and software into vehicles.

Vehicle-to-vehicle communication systems would give cars the ability to warn drivers of dangers as far as 300 yards away. The technology could be linked to safety systems that automatically trigger brakes or make steering adjustments.

The technology would provide a 360-degree view of what's happening around the vehicle. It could, for instance, sense what's happening beyond an obstacle, such as a large truck, while at the same time monitoring cross-traffic at the next intersection.

NHTSA's plan is based on research from an experiment with the University of Michigan Transportation Research Institute using about 3,000 vehicles already sharing information about their speed and location in Ann Arbor, Mich.

The insurance industry lauded the effort.

"The chief advantage is that this technology always pays attention, unlike drivers," said Adrian Lund, president of the Insurance Institute for Highway Safety.

Where federal regulation previously has focused on strengthening the structure of vehicles to protect occupants, this represents a shift toward technology to avoid crashes, Foxx said.

The Transportation Department did not provide any cost estimates.

"The safety benefits here will clearly outweigh any concerns about cost," Foxx said.

The agency is signaling its intentions now because it wants car companies to plan their research around common standards, Lund said. Moreover, it wants the Federal Communications Commission to reserve radio bandwidth for automotive use, and to understand any safety implications of allowing others to use portions of the same radio spectrum, he said.

But it will be years before drivers benefit, he said.

"The timeline for the safety benefits is unfortunately long because you need to have a lot of vehicles broadcasting their speed and direction before this is going to be useful," Lund said. "If only 1% of the cars have this technology, then you are not going to be warned about most of the threats on the road."

Automakers are already working on such systems.

Honda Motor Co. "is working on a variety of vehicle-to-vehicle, vehicle-to-infrastructure and vehicle-to-pedestrian technologies," said Chris Martin, a company spokesman. "We're pretty deep into testing in Japan in conjunction with local governments there."