Metro is installing an $11.5 million network of computerized signs designed to give passengers a real-time description of action on the rails, telling them exactly when the next train will arrive and how long a delay will last.

Agency officials expect that the system--which they say is the most sophisticated of its kind in the country--will be running by March and that some stations will have service by next month.

The message signs mean that passengers waiting on a Metro subway platform no longer will be clueless about whether the next train is near or far, or never coming at all, said Richard A. White, Metro's general manager.

"This will deal with their anxiety and give them a greater sense of comfort," White said. "It will tell them if they just missed a train, if they have time to make a phone call or even run a local errand. If I go to an airport, I want to know if my plane is going to leave on time and if not, why and what's going to happen to it. Now we can provide the same for our customers."

The new system, which is undergoing software tests and has been installed in about half of Metro's 87 stations so far, will consist of 500 signs linked to Metro's main operations computer.

The chocolate-brown signs have yellow light-emitting diode lettering on a 5-foot-by-27-inch screen and are mounted on an eight-foot galvanized steel pole. Some signs, on lower-level platforms, are suspended from the ceiling.

The signs, which also have built-in loudspeakers to carry voice announcements, are designed to be visible from the entrance to the station, so that passengers can read about delays or other problems before they make the decision to pay for a ride and walk through the fare gates.

"In some instances, if we're having an extended delay, they could go to a different station," White said, adding that the signs also can tell passengers whether escalators are out of service.

Metro began considering a computerized message system six years ago, prompted by a provision in the Americans With Disabilities Act that requires subways to have visual information signs for hearing-impaired passengers.

The agency awarded an 18-month, $5.5 million contract to Inova Inc. of Charlottesville in 1996. The contractor ran into a string of technical problems that added time and money to the job, said Kenneth Waller, a Metro supervisor who has overseen much of the project.

While transit systems in Paris, Madrid and other foreign cities have real-time message signs, few in the United States have the technology. New York, the country's largest subway system, installed message boards in some stations but ran into wiring and computer problems and is about three years away from offering real-time information, New York transit spokesman Al O'Leary said.

The Bay Area Rapid Transit District in San Francisco just installed a real-time system about a month ago, but Metro's system is more sophisticated, White said.

Riders waiting for trains beneath the new message sign being tested at Metro Center this week said they welcomed any device that would tell them what's happening on the rails.

"If you're in a hurry and something can tell you if a train is coming any time in your lifetime, well, that's a help," said Peter Alterman, an administrator for the National Institutes of Health, moments before his Orange Line train arrived. "If you know there's a delay and you know how long it is, you can run upstairs and catch a cab. Or I could go and get the Yellow Line, to get around the problem on the Orange Line."

At platforms that serve more than one line, it will be helpful to know in advance if the train that is approaching is the one you want, said Emmanuel Tamen, a lawyer who watched an Orange Line train come through the station as he waited for a Blue Line train. "Right now, everyone crowds up on the platform to see what train it is, because you don't know until it is physically here," he said.

Metro will not sell advertising space on the message boards, White said. Eventually, he said, the agency hopes to connect the message signs to Metro's Web site, so passengers can check the traffic on the rails before heading for a station.

CAPTION: A new video sign is being tested in Metro Center. The signs are designed to be visible from the station entrances, so passengers can know about problems before paying.