They ought to rename the Metro Center subway stop Melting Pot, since everybody who's anybody--and I mean every kind of anybody--seems to pass through there.

And about this time every year, that hardy annual makes his appearance:Washington's springtime tourist. Go down to Metro Center some afternoon and you'll be able to figure jout in a flash which one he is.

He's the one who gets on a train and immediately starts studying the route map, trying to prove to all those doubting urban faces that he, Irving Instamatic, pride of Peoria, can figure out the Red Line with the best of them.

He's the one who tries to keep his Farecard as a souvenir, only to discover that he'll spend the rest of his life in the Rosslyn station if he doesn't feed the card through the exit slot

He's the only person who has ever gotten on or off a train at the Arlington Cemetery station. And the only one who ever will

Most of all, however, he is the Metro passenger most likely to get lost. And the least likely to admit it, or ask for help.

That's where Mike Turpeau comes in.

Turpeau is a 58-year-old government lawyer and a daily Metro commuter. He thinks the problem of lost or confounded tourists could be eliminated, or at least eased, if there were a group called Friends of Metro.

So he has founded it.

The thesis behind it: "If the general ridership doesn't get involved, deterioration may happen," says Turpeau.

"New York is the model of undersirability. Not just the graffiti, but the way people are. If a tourist ever got lost there, he'd be afraid to ask for help because he thinks he might get killed. We can't afford that."

To combat Creeping Callousness, Turpeau proposes to station a member of Friends of Metro at every entrance and exit during tourist season. The volunteer would probably wear a Miss America-style sash as identification. From him or her, the tourist could obtain information and advice without disturbing a glassed-in and often busy kiosk attendant.

Metro hasn't taken a position on Turpeau's idea yet, but as he points out, officials haven't said no out of hand, either.

Friends of Metro might be especially effective, too, at controlling crowds when the subway is jammed (the crush of Solidarity Day comes to mind). Friends members might also serve as auxiliary police officers on days the Redsking play at home, or on holidays when there are fire-works on the Mall.

"It would do wonders for the image of the city," says Turpeau. "It would suggest that we're proud of our subway, and that we depend on it. I can't see how it could miss."

Neither can I. If you're interested in volunteering, write to Mike Turpeau, P.O, Box 208, Washington, D.C., 20044.