An alternative route for the planned expansion of commuter rail service to the South Coast cities of Fall River and New Bedford is gaining traction. 

The MBTA revealed two months ago that the South Coast Rail plan is about $1 billion over budget and seven years behind schedule. These, however, are just the most quantifiable problems the commuter rail expansion faces. Beacon Hill has been talking about extending service to and from Boston for 30 or so years.

In order to get service running in the imaginable future, the state needed to look at alternative routes that don't require an expensive bridge through a swamp in Easton. 

Two alternative routes are being considered. One would be an extension from Stoughton to Taunton with spurs on to New Bedford and Fall River. Another would build off the existing Middleboro line.

That Stoughton plan is gaining momentum with South Coast business groups and some local officials, who told the T board to open the alternative up to public feedback so it can advance into the design phase.

MassDOT Secretary Stephanie Pollack said the T's deliberate planning is "to ensure at this stage that we are in fact pursuing the alternative that will produce the most timely, most cost effective rail connection between Boston and the South Coast as we proceed."

MBTA planners said the trip from Fall River or New Bedford to South Station would take between 75 to 77 minutes.

MBTA staff want to avoid using buses to get people from the coastal cities to existing rail lines, arguing that travel times by bus would be too long for riders.

While the board weighs which alternatives to pursue, plans are in progress to institute interim service from the South Coast to existing rail lines as a temporary fix.

House Transportation Committee chair William Straus of Mattapoisett said he isn't worried by projections placing potential ridership of the South Coast Rail link at only around 4,500 commuters a day.

"This, I think, is a realistic way to start service... the same way the Worcester service started: few trains a day, gauge the impact, then you grow into it," Straus said.

The MBTA Control Board also voted to increase the authorization limit for contracts for further work on the Green Line Extension project to Medford. Work continues on the corridor while the MBTA waits for final word from the Federal Transit Administration about whether or not the redesigned plan is still eligible for $1 billion in federal funds. After hearing from the FTA, the board will need to give final approval to continue the project.