The state’s plan to extend the MBTA’s Green Line to West Medford does not promise enough environmental benefits to justify its cost, according to one panelist at the latest CommonWealth Forum, but public-transit advocates responded that the project is only one of many needed to improve transportation and stimulate economic growth in the Boston area. “End of the Line? Big Dig-Related Transit Projects and the Future of Public Transportation” was held on May 26 at the Omni Parker House Hotel in Boston. CommonWealth editor Robert Keough moderated the discussion.

David Luberoff, executive director of the Rappaport Institute for Greater Boston, restated his argument (see “Dug In,” CW, Spring ’05) that the state should reconsider commitments, made in 1990 to head off opposition to the Big Dig from the Conservation Law Foundation, to extend the Green Line, restore trolley service on the Arborway branch of the Green Line, and connect the Red and Blue lines. “We have gotten so much more pollution reduction out of cleaner cars than you will ever get from the entire combination of the transit projects,” he said.

“The only way we can get out of what the data tells us are probably not great choices is for the advocates of those choices to say, ‘We acted on the best information at the time, and in retrospect we might be wrong,’” said Luberoff, who called per-rider costs of the three projects “awesomely bad.”

But other panelists – all of them contributors to an online forum in response to Luberoff’s article, posted at www. – were by no means willing to say that. Fred Salvucci, former state secretary of transportation and now a lecturer at MIT, said the state would be setting a bad precedent by pulling a “bait and switch” and reneging on its commitments. (This spring the state announced plans to go forward with the Green Line extension but not the two other projects in question.) “This a deal between the Commonwealth and the [Conservation Law Foundation] over three successive administrations,” he said. “The Commonwealth got its part of the deal. The Big Dig proceeded into construction and it is largely built at this point.”

Salvucci added that the debate over the value of public transit should not be limited to air quality estimates. “If we only expand highways and fail to address public transportation,” he said, the Boston metropolitan area would face gridlock conditions as least as bad as those before the Big Dig.

Philip Warburg, president of the Conservation Law Foundation, also objected to the idea that the terms of the 1990 agreement should be revisited. “The Commonwealth has collapsed a debate that should be about all the outstanding transit commitments, which amount to about $1.8 billion, to a debate about which of three projects should be taken off the table,” he said. Warburg pointed out that other terms of the agreement – including additional trains on the Blue and Orange lines – have already been delayed.

Stephen Burrington, undersecretary of the state Office of Commonwealth Development, agreed that more than clean air is at stake, saying that the state was most concerned with getting “the best bang for the buck from the overall transportation and development point of view.”

Ellin Reisner, president of the Somerville Transportation Equity Partnership, said that her city, which is the most densely populated in the state, had “really lousy service,” despite its heavy reliance on public transit. “We have eight rail lines going through Somerville,” she pointed out, but they mostly serve commuter-rail branches that don’t stop in the city. The Green Line extension to West Medford would serve several Somerville neighborhoods, and Reisner said it would help address “pent-up demand” for public transportation.

A detailed summary of the forum provided by State House News Service can be found here.