The MBTA’s former oversight board, the Fiscal and Management Control Board, instructed the agency to begin a low-income fare pilot program by July 2022 at one of its final meetings last summer. Under a new oversight board, which has been meeting since October, the MBTA has not moved forward on the recommendation.

Though included in the Senate bill, the low-income fare mandate was left out of the House’s version of the bill and faces opposition from the House’s top transportation legislator. The two bodies must come to an agreement on the transportation provisions before the Legislature breaks for its summer recess on July 31.

It may also be doomed by Governor Charlie Baker, who vetoed a low-income fare bill passed last year. Aides for Baker did not respond to a request for comment on Friday.

Still, Senator Brendan Crighton, a Lynn Democrat and co-chair of the Legislature’s joint transportation committee, said he’s hopeful a low-income fare will make it through.

“The public transit system needs to work for everyone,” he said. “Right now it does not.”

Also included in the Senate’s bill is $7 million for transit authorities to start fare-free bus programs.

In the absence of movement on transit reform from Beacon Hill, some lawmakers said the state’s transit agencies don’t need to wait for a legislative mandate to experiment with discounted fares.

“The MBTA and [Regional Transit Authorities] don’t actually need authorization from the Legislature,” said state Senator Sonia Chang-Díaz, a Jamaica Plain Democrat who recently ended a campaign for governor. “They could have done it all along.”

Several municipalities and transit agencies are already experimenting with fare-free bus transit, including Boston and the Merrimack Valley Regional Transit Authority.

Some experts characterize transit fare as “the most regressive” revenue in the state, as it makes up a far more significant portion of spending by low-income earners than it does of those with higher salaries.

“A $2 or $3 fare seems like something you’d drop in the jar after lunch to a wealthier person, but it can be the decider of whether you are going to go to an extra job interview for a low-income person,” said Phineas Baxandall, a senior tax analyst at the left-leaning Massachusetts Budget and Policy Center.

Stacy Thompson, executive director of LivableStreets Alliance, a public transportation advocacy group, said low-income fares aim to keep money in the pockets of people who need it most, and eliminating bus fares can boost ridership and make service more reliable by reducing the time it takes people to board.

“They’re different; we need both, they solve different problems,” she said.

But even initiatives like mandating the creation of a low-income fare program are just “partial wins,” some advocates say.

With profound safety problems at the MBTA that have been elevated to the point of a federal investigation, riders and advocates worry that those problems will translate into an excuse to push fare accessibility off another year.

“They are good ideas, but the Legislature will actually need to put forward the resources,” said Jonathan Cohn of Progressive Massachusetts.

Resources are a top concern of Representative William Straus, a Mattapoisett Democrat and co-chair of the joint transportation committee, who said he is focused on safety at the MBTA. The committee is holding an oversight hearing with the state’s top transportation officials on Monday.

“Putting the MBTA in a situation of increased unknowns at a time when, at least for me, the first goal is public confidence in the safety of the system, adding another unknown in terms of its financial status, doesn’t seem like the right time,” he said.

Crighton said funding for a low-income fare program can be worked on later. The T could face a $236 million budget gap next summer when federal COVID-19 relief funds run out.

“There are a lot of challenges,” he said. “This is one we know how to solve: giving people the ability to get on the T.”

In response to intense pressure to provide relief to families squeezed by inflation, Massachusetts lawmakers passed a proposal to increase the child and dependent care tax credit, the earned income tax credit, the senior circuit breaker tax credit, and provide for rental assistance. The plan also involves giving potentially millions of taxpayers a one-time rebate of $250, or $500 for some dual-income households.

However, the plan excludes the state’s lowest income residents — those who report less than $38,000 in annual income.

Transportation advocates who say a low-income fare is long overdue are still hopeful that the final transportation bond bill will include the mandate, which could provide ongoing financial relief for people.

An MIT study in 2019 found that MBTA riders who paid lower fares took about 30 percent more trips — including trips to health care and social services facilities.

“With the cost of gas, cost of groceries going up, that’s real savings for a lot of people,” said Pete Wilson, a senior adviser at Transportation for Massachusetts. “We all talked about essential workers through the height of the pandemic, let’s actually do something for these people.”

Boston Senator Lydia Edwards, who filed the low-income fare amendment in her chamber, said while it’s possible Baker will veto the idea again, the amendment could still keep the conversation around low-income fare alive, and underscore the legislative will to act on it in the near future.

Baker is not running for reelection this fall, and presumptive Democratic nominee Attorney General Maura Healey is widely considered to be the frontrunner in the race.

“When Maura Healey is governor, we’ll have no excuse,” Edwards said.