A vast underground extension to Grand Central Terminal that allows commuters to exit as far north as 48th Street opened yesterday, giving tens of thousands of train riders the chance to shave crucial time off their daily commuting.
But instead of fanfare and a ribbon-cutting ceremony heralding the change, the long-awaited Grand Central North opened in relative secrecy to avoid ''mass confusion,'' said Donna Evans, a spokeswoman for Metro-North, a division of the Metropolitan Transportation Authority.
Until yesterday, commuters at Grand Central could exit only through the terminal. Because of the way the trains come into the station, that forced many people working in midtown to go south after their arrival and then retrace their route northward outside. But with the changes, commuters can just head straight to their jobs or other destinations, without the detour.
''It's the greatest idea in the world,'' said Brian Hyland, a salesman from Norwalk, Conn. ''I had known and heard about it for years. It's beautiful.''
Metro-North officials estimated that commuters using the passageway would cut an average of 10 to 15 minutes off their daily commuting time. They expected the new route to be so popular that they refrained from heavily publicizing its opening so that things went smoothly.
''The advantage to starting small is that it is a complex facility,'' Ms. Evans said. ''We can get people used to it in smaller segments.''
And so, during yesterday morning's rush, only 7,000 of the anticipated 35,000 commuters traipsed north through the gleaming new underground walkways toward their jobs and elsewhere farther uptown.
For the evening rush, traffic picked up a bit, with about 9,000 commuters racing past the new terrazzo walls adorned with mosaic, glass and bronze panels depicting the nighttime sky.
Between peak times, some commuters drifted through to admire the new extension, somewhat bewildered by the sudden change in their daily routines. Most were there to map out the fastest routes of travel to and from their offices.
Grand Central North, which cost $112 million to build, is a three-level labyrinth with two walkways that run parallel to the Metro-North train tracks, and two passageways that run perpendicular. The corridors allow commuters to walk underground from 42d Street all the way to 48th Street and Park Avenue, the farthest uptown exit. There are also exits at 47th Street at Madison Avenue and on the east and west sides of Park Avenue between 45th and 46th Streets.
Yesterday, commuters tried to find their train platforms with a mixture of awe and confusion despite piles of maps being distributed by Metro-North employees.
''I think it is beautiful,'' said Priscilla Forte, who works at 55th Street and Madison Avenue. ''I love the way it works. I have no idea where my train track is, and I can't find my way out of here, but maybe I'll get more of a feel for how it's laid out.''
Like Ms. Forte, Joe Nesci was pleased -- but lost. ''Well, so far it looks good,'' he said. ''If I could only find my way out.''
The empty passageways made for some odd scenes, at least for New York. Aside from being clean, well lighted, clearly marked and weatherproof, the corridors have pay telephones. Rows of them. And they work.
As veteran commuters looked for train platforms, tourists searched for help. The empty corridors and remarkable absence of crush in the middle of midtown convinced Sandra Menturs that she was lost.
''Something's wrong here,'' said Ms. Menturs, who is from Chicago. ''You never go anywhere in New York unless there's hundreds accompanying you. There's nobody here and there's millions up above.''
She had just come from the main concourse, which was not actually above but on the same level.
Others, like Mr. Hyland, came simply to do reconnaissance.
''It's new, and it's something I'm definitely going to be using,'' he said, ''so I want to get a heads up on how much it will save me.''
The saving, of course, was in time, not money, a precious resource in itself for New Yorkers.
But many commuters were counting minutes, some with enthusiasm, some with skepticism.
''It was supposed to shorten my commute by 10 minutes, but I doubt it,'' said Jack Low, on the run to catch a train.
