Our suburban contemporary, The Montgomery Journal, reported the other day that a man accused of shoplifting at Montgomery Mall had been convicted after one of his alibi witnesses testified that she had arrived at the Mall via the Metro subway.

It's true the subway doesn't go anywhere near there. My own theory is that the witness may have thought she was at the mall, perhaps the result of one of those congenitally misleading train destination signs.

Which brings us to the letter to the editor Monday by two Virginia Metro directors. They advised Post readers that when the Blue Line extension opens from National Airport through Alexandria next fall, it will be served by Yellow Line trains.

Let's run that past again: Unless there's a change of plans, eastbound Blue Line trains will end up on the Orange Line; westbound Orange Line trains will end up on the Blue Line; eastbound Orange Line trains will end up on the Blue Line; westbound Blue Line trains will end up on the Orange Line; northbound trains from the Blue Line's Huntington Terminal will end up on the Yellow Line, and southbound Yellow Line trains will become Blue and go to Huntington.

There's one bit of solace, however. The Red Line tracks don't go anywhere but to stations on the Red Line, despite the Orange destination sign the other day that said the Red train we boarded was going to "W Falls Church."

For further information, call Metro information at 637-2437.