Take the Red Line to Park St.

Those words form a familiar refrain for everyone who has ever tried to get away from Harvard on the Boston subway system. All four lines--Red, Blue, Green and Orange--run directly through the center of Boston. Even as simple a trip as traveling from one side Cambridge to another requires a lengthy detour the inevitable Park St. stop.

But a study currently under review by the Massachusetts Bay Transportation Authority (MBTA) proposes a simple solution to the problem--building a fifth line on the outskirts of the city to connect outlying areas. Similar proposals for a "circumferential" transit route have been debated in Boston since 1972.

"That kind of thing has been studied for years," said Jose A. Gomez-Ibanez, a professor of urban planning and public police at the Graduate School of Design. Proposals for a circumferential route have usually been rejected, he said, because "it would cost mucho buckos."

According to the MBTA feasibility study released last week, building a circumferential rail line would cost more than $4.5 billion. Even if approved, the line would not be completed until 2010, said MBTA project coordinator Esther A. Johnson.

The proposed line would extend the Orange Line from Charlestown to the Green Line at Lechmere, cut across the city to the Red Line at Kendall Square and turn across the river to Boston University.

Michael H. Rosenberg, head of the city's Community Development Department, said yesterday that the plan would benefit the city by reducing the traffic congestion caused by large developments at Kendall and Lechmere Squares.

But some city residents said the plan would only provide the city with increased opportunities to redevelop areas near residential communities.

"Normally you would expect a new transit line to reduce traffic," said Stephen H. Kaiser, an independent traffic engineer who has opposed the project. "But this would increase traffic because it serves as a stimulation for development."

Since the mid-1970s, most development has occurred in the areas served by the Red Line, which runs along Mass. Ave. But Rosenberg said the new route would not open up many new sites for commercial development.

"I would not want the city to increase its development because of the circumferential line," said Rosenberg. "I don't see it as a tool for economic expansion. I see it as a tool for limiting traffic."

But Gomez-Ibarez, an expert in light-rail transit, said the new line would probably not ease the city's traffic problems.

"My perception--and it's only a resident's perception--is that what's increased traffic is the people coming into Kendall Square," said Gomez-Ibarez. "How much better served could Kendall Square be than with that Red Line?"

Gomez-Ibarez also said he disagreed with the MBTA's assumption that a circumferential route is needed. The expense of the new route would far outweigh the number of riders it could be expected to attract, he said.

In addition, other public service projects--the Boston Harbor cleanup and construction of the Central Artery--will receive the state's top priority in the next few years.

"It sounds like a lot of money for a low probability of picking people up," Gomez-Ibarrez said.