McLean, Va. ? Federal highway officials think they’ve found a way to prevent thousands of traffic accidents every year: “smart intersections” that warn drivers they’re about to run a red light or smash into a truck.

Government drivers demonstrated this week at the nation’s first test intersection just what the intersection of the future will be able to do.

This smart intersection designed by the Virginia Technical Transportation Institute includes traffic signals and an advanced traffic controller system. The technology was unveiled this week at the Federal Highway Administration's Highway Research Center in McLean, Va.

A car speeds toward an intersection, about to collide with a van. Sensors spot the car as it approaches the red light and emit a signal to the car, which triggers a high-pitched beep and a red light on the dashboard that says, emphatically, “STOP.”

Federal Highway Administration officials believe it will prevent thousands of traffic accidents every year.

Much testing remains to be done, and drivers probably won’t see smart intersections for another five years, say highway officials.

The newly paved intersection at the administration’s Highway Research Center includes traffic signals, an advanced traffic controller system and two roads from nowhere converging in the middle of the agency’s office campus in this Washington suburb.

“It’s not a ‘You can stop worrying, the car will drive itself’,” said Jeffrey Paniati, associate administrator for Federal Highway. “It’s a ‘We’ll help you drive.”‘

The technology isn’t all that new, say highway officials. Already on the road are smart cars and trucks that alert somnolent drivers, call for help in an accident and even take over some of the driving.

What is new is behavioral research into how people interact with traffic signs and warning systems in their cars.

Engineers are experimenting with bells, speech-related devices and systems that make cars shake as if they’re driving over a rumble strip, Paniati said.

An elderly driver in a Lincoln Continental on a country road might respond to different stimuli than an 18-year-old in a Camaro on prom night. “We’re looking at all the options to find out when to give warnings and who responds to what,” Paniati said.

Engineers, for example, are studying the ideal pulse rate for a flashing “No left turn” sign to activate neurons in a driver’s brain, according to James Misener, an engineer with the University of California at Berkeley.

Here’s how the sign works at the test intersection:

As Driver A begins to make a left turn, Driver B starts to go straight through the intersection from the left. Their movement is transmitted through sensors in the pavement to an advanced traffic controller, which figures out that Driver A shouldn’t be making that left turn yet and activates the eye-level street sign.

“When the two systems start talking to each other, we can exponentially save lives,” said Mary Peters, Federal Highway administrator.

Driver error is the leading cause of the 6 million crashes in the United States every year. About 4.5 million of those fall into three categories: 30 percent are rear-end collisions, 20 percent are run-off-the-road crashes and about 25 percent happen at intersections.