The MBTA Commuter Rail line from Readville to South Station is free for the next two weeks. The effort to boost the line's ridership is bolstered by an unusual benefactor.

The Fairmount line is the only route completely inside Boston's city limits, carrying riders from the furthest outlying neighborhood through Dorchester to downtown in about a half hour. 

After years of low ridership, community activists turned to U.S. Rep. Michael Capuano to pay for a two week period from May 8 to May 21, where rides will be free. Capuano's paying the $53,000 price tag for the promotion from his campaign account.

Capuano says he wants his constituents to know the line is reliable, fast and costs the same as the subway:

"Nothing is free in life. This is a temporary thing to try to change people's travel habits. That's all it is," Capuano said at an event Friday introducing the free service.

Capuano said he doesn't expect any political benefit from his campaign's donation and it was "time to put my money where my mouth is."

The line has been one of the least reliable routes in the Commuter Rail system, but officials and Dorchester riders say the train is now 96 percent on-time. The Boston Globe reported in October that trips on the line were cancelled far more frequently than other routes.

Dorchester state Rep. Russell Holmes said the problems with Keolis, the private company that operates the Commuter Rail, have been addressed and service is up to par for his constituents.

"[Keolis managers] stood right up and went right to the neighborhood and was just candid. Here's the problem. Here's how we're going to resolve it and it just won't happen again. And true to their word, it hasn't happened again

"To have the most reliable line coming through our neighborhood is exactly what I want to push people towards," Holmes said.