Their specific requests varied, but the roughly half-dozen mayors and state lawmakers who addressed the MBTA’s oversight board on Monday all echoed a common theme: Expanding service and connectivity on the commuter rail will bring significant benefits for the riding public.

Boston Mayor Marty Walsh kicked off the advocacy, voicing his support at the meeting for running more frequent trains on the Fairmount Line and transforming the current wheel-and-spoke commuter rail system into one with trains running more regularly in both directions.

The T is considering a range of pilot programs that communities have pitched, including Boston’s suggestion to run eight additional trains on the Fairmount Line that runs through the city’s eastern and southern neighborhoods.

“Every time we increase access, increase service, and increase equity in our system, the residents of Boston respond with increased use and increased support of the system,” Walsh told the board. “They’re eager for more.”

The calls for expanded service came at the same meeting where MBTA officials described an exploding midyear budget deficit, now pegged at $53 million, and as House lawmakers prepare for a debate sometime this fall on possible new sources of transportation revenues.

No decision on the Fairmount pilot’s fate was reached on Monday, but supporters described it as an essential strategy to meet the region’s needs. The Fairmount Line, built as mitigation from the Big Dig project, serves a large, diverse portion of the city — 83 percent of residents along the line are people of color — that is generally inaccessible by subway.

“These neighborhoods have been overlooked for far too long,” said Staci Rubin, an attorney with the Conservation Law Foundation.
While most of the line’s stations are in Zone 1A and therefore cost the same amount to use as a subway ticket, advocates want to see trains run more frequently so that commuters will be more encouraged to use it.

Members of the Legislature’s Boston delegation filed a bill (H 2985) that would require the Department of Transportation to conduct a two-year program on the line with trains every 15 minutes at peak and every 30 minutes off peak. The legislation has yet to be taken up by the Transportation Committee.

Rep. Dan Cullinane, one of the bill’s authors, told the T’s board that making the Fairmount Line operate in a manner similar to rapid transit would be an “incredibly important” boost to commuters in the city. He also asked the MBTA to allow full use of CharlieCards rather than commuter rail tickets on board.

“Let’s remove the last hurdle for people riding the line,” he said.

The board is set to vote on new pilot programs, including the one suggested by Boston, in January. However, members suggested on Monday that it may be worth scheduling a vote on the Fairmount project by the end of this year so a test run could begin in spring 2020.

A separate pilot program extending weekday Fairmount Line service to Foxborough, which includes lower prices for reverse commuters, begins this month.

Walsh has been vocal about his desire to see improvements on the MBTA. During months of Red Line delays this summer after a derailment, the mayor described the system as “not currently a functional service.”

With infrastructure aging and roadway congestion near a breaking point, scrutiny has been high on the MBTA and what investments it will — or can afford to — make.

In addition to Walsh, both Lynn Mayor Thomas McGee and Everett Mayor Carlo DeMaria Jr. implored the board to support programs that would extend rail service to their communities, which are often overwhelmed by drivers cutting through to get to Boston.

“We bear a disproportionate burden of the region’s transportation system, but reap few of the benefits,” DeMaria said. “Two miles of commuter rail tracks and 70 trains each day pass through Everett but do not serve the community. We host large-scale maintenance facilities critical to maintaining tracks and trains that do not serve or operate in Everett.”

The T is studying long-term transformations to the commuter rail, ranging from running some trains more frequently to electrifying the whole system. Costs vary, too, with likely price tags of $1.7 billion in 2020 capital dollars for the simplest option to $28.9 billion for the most dramatic system overhaul, according to figures presented during Monday’s meeting.

Walsh called for the MBTA to embrace a plan that would use electric trains in place of the existing diesel vehicles and run high-frequency service inside Route 128. He said that change could help take cars off the road and mitigate the constant headache of traffic.

Asked about how such a project’s significant price tag could be handled, Walsh said he believes lawmakers — whose House members are preparing this fall to embark on a still-undefined debate about transportation funding — need to identify a new dedicated revenue source for public transit.

“We have to have a serious conversation about revenue,” Walsh, who said one of his last votes as a state representative was in favor of raising the gas tax, told reporters. “You need to have a dedicated revenue source because the issue’s not going to go away, and if you don’t address it now, it’s only going to get worse, which means the bill is going to get higher.”