Judging by a persistent trickle of reader mail and my own recent visit there, the Archives station on Metrorail's Yellow Line must be the most confusing for passengers on the subway system.

Alone among the stations that don't serve as end-of-the-line terminals, Archives -- near Seventh Street and Pennsylvania Avenue NW -- has trains running in both directions on each of its two tracks.

As you ride the escalator down from the mezzanine to the train platform, you find the pylons common to all Metro stations. The arrows on the pylon alongside the lefthand (northbound) track point to trains destined for Gallery Place, one station to the north. The arrows alongside the righthand (southbound) track point to trains destined for Huntington via the Pentagon and National Airport.

On my recent visit to Archives, there were no fewer than three passengers visibly baffled by the observable fact that the signs were at least half-wrong -- that trains were running willy-nilly in either direction on both tracks.

Why? The answer actually is simple, though it sounds complicated, according to Metro officials.

Gallery Place, the present downtown Yellow Line terminus located one station to the north of Archives, is now the temporary end of a line that ultimately will carry trains into Prince George's County. The switches that move trains from one track to another, putting them on the correct track for the return trip to Virginia, are south of the Archives station -- not to the north, between it and Gallery Place.

Ergo, any switching of a train from one track to the other must be done south of Archives. The train then moves into and out of Gallery Place on either track, depending on whether the other track already is occupied.

But that begs a question to Metro: why not erect signs at the top and bottom of the escalator that say something like: "Trains in both directions run on either track. Check the train destination signs."