Anyone who has bounced up and down the Northeast on a Metroliner in the last decade or so while reading Amtrak's reassuring messages about ongoing improvements in the track system will have had a disconsolate thought now and again concerning the decline of American ingenuity and efficiency. An industry that somehow managed to span a continent with rails in but a few years seems to be taking forever to lay new ones between Washington and Boston.

But there is very good news concerning the railroad stations along this still well-traveled line--those great outposts of excitement left over from a more optimistic age that for years have been going gradually to seed or worse. Today, if you stand in the newly bright main hall of Baltimore's Penn Station, a place with bulging Doric columns and glistening marble walls and shining saucer-dome skylights, you will feel more like celebrating than carping.

This is because today, with interior renovations almost complete, Penn Station has again become what an urban railroad station should be--a welcoming event, a ticket to faraway places (even if they're really not so far away), a clean well-lighted space that adds a touch of sober romance--if it weren't so respectable it would hardly be Baltimore--to the sometimes humdrum business of leaving or entering the city on a train.

The story behind the story is one of constant conflict between transportation engineers who believe that the beauty of the existing stations has nothing to do with "speed and dependability of intercity rail passenger service"--that is the language of the Northeast Corridor Improvement Project adopted by Congress in 1976--and those with broader visions of travel. If they could have, the engineers would have spent all of the $2.65 billion appropriated for the project on nuts and bolts, leaving nothing from this vast sum for "cosmetic" improvements of the ill-maintained older stations.

Fortunately, with occasional proddings about lessons learned from the destruction of Pennsylvania Station in New York and the desecration of Washington's Union Station, the wise if lead-footed shepherds of the project took the broader view. As a result the revival of the Baltimore station is an enlightened harbinger of things to come, for similar things are happening at other stops--eight of them registered, national historic landmarks--along the way.

Occasional users of the place who have not been there in, say, a year or so, will be delighted by the change, for grime and confusion have been replaced with order and light in the 72-year-old Baltimore station.

The outside of the building is not its strong point--it's acceptable, not masterful. Designed by Kenneth M. Murchison, a New York architect trained at the turn of the century in the Ecole des Beaux Arts in Paris, its main elevation is a rather standard Beaux Arts scheme with symmetrical wings flanking a central mass with rounded entrance arches, a two-story colonnade of double Tuscan columns and a conventional attic story decorated with an ornate clock. The strangest thing about the place is no fault of Murchison's. The building sits upon an isolated island above the railroad tracks and at an angle to the grid of the city's streets--an odd place for a building, and especially a Beaux Arts building.

But the inside of the building is quite a treat, particularly the main hall, a Doric atrium sheathed in white marble underneath three saucer-dome skylights made of translucent leaded-glass segments punctuated with bright fruit garlands. Somewhere along the line, perhaps as part of blackout preparations during World War II, someone covered the skylights with a coat of tan paint. This added a strange, golden glow to the unwashed yellowing walls. Sparkling lightness is the special mark of the place in its reincarnation.

For this and other niceties of the transformation, including the supervision of the re-manufacture of Rookwood tiles for the concourse part of the building and the introduction of an appropriately antiquated typeface on all the signs (Garamond bold, invented in 1539 and definitely avec-serif), credit is due to the Washington office of Skidmore, Owings and Merrill (David Childs, partner, and Theodore Oldham, senior designer for the Baltimore station).

The local office of SOM, in fact, is in charge of design for all of the stations in the northeast corridor program (with Marilyn Taylor as project architect for the whole affair). This is a huge responsibility that involves renovating buildings by a number of the better architects in our history--Frank Furness in Wilmington, Del.; McKim, Mead and White in Newark; Cass Gilbert in New Haven, Conn.; and H.H. Richardson in New London, Conn.--as well as a completely new station in Providence, R.I.

If the work done so far on Baltimore's station is a fair guide, the SOM approach is a combination of well-researched restoration, cost-conscious compromise, intelligent space planning and good urban design. The Baltimore job is not a worshipful re-creation stone-by-stone--for evidence of compromises, the first place to look is to the concourse ceiling--but it focuses attention on the right places.

Still to come are renovations of the outside of the building, much-needed though not extensive. Unfortunately the problem of at last giving the building a proper setting, though easily solved by building a bridge right up to the entrance, must await the miraculous appearance of some funding godmother (or father) in the sky.

On the other hand, Baltimore Mayor William Donald Schaefer has been known to precipitate such miracles from time to time. Why is the Baltimore station the first to be finished along the entire corridor? SOM's Marilyn Taylor, for one, says that Schaefer is the answer: "He comes out and makes the speeches and pushes people and gets things done." Perhaps there's a way to get him to work on Union Station, or even on those ever-delayed Am-tracks.