As a safety demonstration, it was a heart-stopper: A Ford Taurus was seconds away from cruising through an intersection when suddenly a row of red lights pulsed on the lower windshield and a warning blared that another car was approaching fast on the cross street.
Braking quickly, the driver stopped just as the second car, previously unseen behind a large parked truck, barreled through a red light and across the Ford's path.
The display at a recent transportation conference was a peek into the future of automotive safety: cars that talk to each other and warn drivers of impending collisions. Later this summer, the government is launching a yearlong, real-world test involving nearly 3,000 cars, trucks and buses using volunteer drivers in Ann Arbor, Mich.
The vehicles will be equipped to continuously communicate over wireless networks, exchanging information on location, direction and speed 10 times a second with other similarly equipped cars within about 1,000 feet. A computer analyzes the information and issues danger warnings to drivers, often before they can see the other vehicle.
On roadways today, the Taurus in the demonstration likely would have been "T-boned" -- slammed in the side by the other car. There were more than 7,800 fatal intersection accidents on U.S. roadways in 2010.
Called vehicle-to-vehicle communication, or V2V, more advanced versions of the systems can take control of a car to prevent an accident by applying brakes when the driver reacts too slowly to a warning.
V2V "is our next evolutionary step -- to make sure the crash never happens in the first place, which is, frankly, the best safety scenario we can all hope for," said David Strickland, administrator of the National Highway Traffic Safety Administration.
V2V technology holds the potential to help in most crashes that aren't alcohol or drug related, Strickland said. But a lot will depend on how drivers respond to the warnings, and that's one reason for the Ann Arbor test. Overall, more than 32,000 people were killed in traffic accidents last year.
In addition to warning of cars running red lights or stop signs, "connected cars" can let drivers know if they don't have time to make a left turn because of oncoming traffic. When driving on a two-lane road, the systems warn when passing is unsafe because of oncoming cars -- even vehicles around a curve that the driver can't see yet.
The technology is already available, said Rob Strassburger, vice president for safety of the Alliance of Automobile Manufacturers. He said what's needed is for the government to set standards so that all automakers use compatible technology.
The safety benefits of V2V won't be fully realized until there is a critical mass of cars on the road that can talk to each other, and just where that point lies isn't known. By the time the government sets standards and automakers are able to respond, it may be 10 years before the technology is widely available on new cars. It takes about 30 years for a new technology to work its way into the entire population of cars.