By Nicole Dungca GLOBE STAFF DECEMBER 07, 2015

Public transportation advocates and union leaders are bracing for an array of cost-saving proposals from the Massachusetts Bay Transportation Authority as it struggles to balance its budget.

The MBTA is considering more than two dozen options to dig its way out of a shortfall, including hiking fares by more than 5 percent, offering retirement incentives to seasoned workers, and delaying promised wages for its workers.

Officials recently released 27 ideas to help balance the T’s budget, such as ending late-night service and eliminating some trips on the MBTA’s service for disabled customers.

Agency officials have not formally proposed any of the cost-saving moves, and the agency’s control board, appointed by Governor Charlie Baker, would have to sign off on many of the changes.

But some advocates for public transportation are already warily eyeing the options, saying that many would have big implications for riders.

“If Baker’s control board proposes significant fare increases and service cuts, it would be a big blow to all of us who use the T, particularly after this winter,” said Kristina Egan, director of the Transportation For Massachusetts advocacy group.

Brian Shortsleeve, the MBTA’s chief administrator, said the MBTA will need to get “leaner and meaner” as the agency seeks to fill a budget deficit. If the MBTA grows at its current rate, he said, the agency’s operating expenses will increase by about $164 million in the 2016 and 2017 fiscal years — and that could lead to a $242 million deficit in fiscal 2017.

Under the law that created the control board that now oversees the MBTA, board members are directed to pursue a strict financial goal for fiscal 2017: Instead of relying on extra money from the Legislature, they must balance the T’s budget primarily through cutting costs and getting more revenue from fare hikes, real estate, advertising, and other sources.

That’s why the MBTA has been considering fare hikes, raising prices on a service for disabled riders, reducing late-night service or weekend commuter rail service, and a number of other choices that have riled up riders. Officials say that putting 18 of the 27 identified cost-saving measures into effect could save $128.3 million to $191.5 million.

The MBTA has not released figures on how high fares could rise, but the list of cost-saving moves included increasing fares beyond 5 percent.

The MBTA could also go back on promises to workers, such as raises that were to be granted in fiscal 2017. According to figures from the MBTA, deferring raises for several labor groups could save between $5.4 million and $10.9 million.

Officials have also sought to make changes to overtime wages for workers, which could save between $3.8 million and $7.5 million for the agency.

James O’Brien, president of the Boston Carmen’s Union, the agency’s largest labor group, appeared open to some of the ideas. He said he has been having “high-level discussions” with the agency over possibly reopening its contract, which expires in July 2018.

“They’re looking to save money, and we’re looking for some guarantees for our membership,” he said, declining to specify what kinds of guarantees.

Shortsleeve said the agency is considering a retirement incentive program similar to one recently offered to state workers, but wasn’t able to quantify how much it would save.

The agency could also freeze wages for its nonunion workers and stop hiring for jobs that have been left unfilled or vacant. Shortsleeve said the agency had asked department heads whether they could leave some of their positions vacant in 2017 to save money, and that eliminating unfilled or vacant positions could save about $15.5 million.

But the job cuts would also come at a time when the MBTA is under fire for not properly training enough staff to deal with the project that would extend the Green Line trolley an additional 4.7 miles into Somerville and Medford. Last week consultants told the MBTA that the agency had not dedicated enough staff to oversee the massive project.

Shortsleeve downplayed the effect retirement incentives or attrition would have on the agency. He said officials would focus on keeping drivers and others who dealt directly with providing transit.

“What matters is the efficiency in which we move, the speed in which we can make decisions,” he said.

Nicole Dungca can be reached at nicole.dungca@globe.com. Follow her on Twitter @ndungca.