It is a situation infuriatingly familiar to subway riders on the Blue and Orange Lines: A train pulls up to a station platform and who can say for sure where it's going? An orange sign on the front of the train says its destination is Ballston. Its cars are alternately marked Ballston in orange, Addison Road in blue, and "No Passengers."

Waiting commuters shout questions about the train's true identify to people already aboard or just take a chance, stepping in and waiting for the muffled announcements that come by loudspeaker. If it's the wrong train, they get off at the next station and try again.

Yesterday, as Metro board member Marie Travesky complained that the sign confusion is keeping people off the trains, General Manager Richard Page promised that relief is coming. Plans are afoot to begin replacing the offending signs by this winter, he said.

The automated signs have malfunctioned for years -- part of the reason for the loudspeaker announcements. But the recent flip-flop of the Blue and Orange lines' suburban extensions has brought the issue back to the public mind with force, aided by transit officials' blithe advice that passengers check the destination signs before boarding.

Rail operations chief Joe Sheard concedes that that doesn't work. Recently he tried to catch a Blue Line train on Metro Center's lower platform, which is served by both the Blue and Orange lines.

"I hit a train that was exactly half and half and I jumped on," he recalled. Like many commuters, he gambled wrong, but was able to get off at Rossyln to change.

The train's destinations are written on long plastic scrolls (called "curtains" in the subway business) that can hold up to 52 names. In theory, all signs on a given train roll automatically to the desired station name on electronic command from Metro's control room or from the train's operator.

Simultaneously, subway route maps visible to riders inside the cars are supposed to advance to the right route for that particular run. Used since 1976, when the system opened with the downtown Red Line segment, the signs were called yet another example of state-of-the art technology in Washington's subways.

Five years later, Metro officials complained of design problems. To perform routine maintenance, like replacing a lightbulb, crews must remove scrolls, and in doing so often scratch symbols on their delicate surfaces. Electronic sensors use these symbols to identify the desired station name as a motor advances the scroll past it.

Damaged symbols often mean the sensor can't read a station name. Sometimes a scroll runs through three times as the sensor searches, then shuts off the motor. Faulty lines between Metro's command center and the trains also misdirect the scrolls.

"You can find them stopped in crazy positions," says Sheard.

Thus subway cars are occasionally seen marked Dulles Airport -- a place that is miles from any Metro track, planned or finished. That destination was put in years ago on the chance that rail service might one day extend that far.

Sheard says his car maintenance staff is about 15 percent below desired levels. Thus compressors, brakes and air conditioning get attention before the signs. But early this month, Metro moved on the problem, spurred by the need for Van Ness signs for the scheduled Red Line extension to that station in December.

It requested bids for new 18-destination scrolls. Interior route maps are to be removed entirely, simplifying the machines' mechanical innards. That, it is hoped, will decrease maintenence, Sheard said, and damage to the scrolls. Meanwhile, technicians will also try to iron out bugs in the command lines.

Replacing 900 scrolls (there are three on each of Metro's 300 cars) will cost between $75,000 and $100,000, Sheard estimates. Installation is expected to begin before December. For the late 1980s, Metrorail will examine electronic displays of destinations. Currently 10 Metrobuses are using such equipment experimentally.

In other business yesterday, the board approved a transfer scheme between Metrobuses and the two "Jitneybuses" operated by Fairfax County in the Oakton-Vienna-Tysons Corner area. The plans will give Jitneybus passengers 25 cents off on their Metrobus fares; transfers obtained aboard a Metrobus will allow the passenger to ride free on a Jitneybus.