THE MBTA’S struggles with hiring and retaining workers have grabbed headlines for months, but supporters of a new labor deal featuring pay and benefit upgrades say it represents cause for hope that the T will eventually secure the workforce needed to ensure quality service.

The tentative four-year agreement includes a raise that totals 18 percent over four years, Gov. Maura Healey said Wednesday morning at the MBTA Cabot Yard in South Boston. This will be the largest pay increase for T workers since the 1990s, she said.

The contract with Boston Carmen’s ATU Local 589, which represents bus, trolley, and train drivers, rail repair and track maintenance workers, and other “frontline workers” also includes “select targeted increases aimed at hard-to-fill positions such as welders and overnight shifts,” the union said.

Healey announced the agreement also includes better pay progressions for new hires and sign-on bonuses, adds 10 days of paid parental leave, expands bereavement leave to include domestic partners, and offers dental and vision health care coverage for part-time workers.

The union also praised the deal for setting a framework to improve employee restroom access and clarifying legal language around rider assault, which has become more frequent in recent years.

The new contract, which the MBTA board of directors plans to vote on during its meeting Thursday, comes on the heels of a “prior side letter” that allows bus operators to be hired full-time rather than part-time, the union said on Tuesday afternoon.

“This agreement is an investment in a safe, reliable public transit system in Massachusetts. It’s an investment in the world class transit we need for our economy, our quality of life and our environment,” Healey said. “T jobs need to be great, desirable in order to attract, support, and keep the workers we need to get the job done.”

The projected first year cost for the contract is $19 million, with the total projected cost reaching up to $55 million, according to MBTA spokesperson Joe Pesaturo.

When asked if the T would need to raise fares to afford the new contract, MBTA General Manager Phil Eng replied, “I don’t think we need to.”

“We’re certainly confident that the funding will be in place. The Legislature has given us $181 million, I believe, in this budget, that we’re looking forward to taking advantage of and helping further our needs,” he said.

The T has faced frequent service disruptions and safety issues over the last year, including partial line closures, slow service and early shutdowns affecting riders this summer.

System-wide hiring troubles have held the T back from resuming service at regular levels and Healey pledged in her inaugural address to hire an additional 1,000 MBTA employees before the end of her first year in office. Her office later said that the additional funding to hire these 1,000 people was included in money that lawmakers and former Gov. Charlie Baker agreed to steer to the T last year.

The Mass. Taxpayers Foundation estimated in April that the T needed to hire 2,800 workers by next April in order to maintain system operations.

Eng said Wednesday that the T is on track to hire about 1,300 new employees by the end of the year.

“With this new contract, with five months to go, we hope to change those numbers,” Eng said.

He added that the number of incoming bus operators is growing each month.

In addition to changing bus driving jobs from part-time to full-time, the T is also increasing pay rates to $30 an hour, plus overtime and retirement plan and pension contribution. Drivers are also receiving $7,500 sign-on bonuses, paid commercial driver’s license training for between $3,500 and $5,200, $10,000 in tuition reimbursement and expanded health benefits.

Eng and Healey both said Wednesday that their focus is not just on bringing new people on, but also retaining the workforce the T already has.

Alix Gaston, a bus operator since 2004 and shop steward for Boston Carmen’s ATU Local 589, said he appreciated that the deal also creates longevity incentives, instead of just rewarding new hires.

Employees will get financial incentives at 10, 15, 20, and 25 years at the MBTA, he said, excitedly adding that he’s up for his 20th year soon.

“Previously when we supported governors, those governors never held their word,” Gaston said. “We endorsed [Healey], we made sure to show up with signs and everything else. Transportation was one of her running points, and right now she’s definitely showing that she meant what she said.”

Eng alluded to “the disinvestment that’s gone on” at the T in recent years, saying “it’s gotten to the point where we need to reinvest in our workforce.”

“We have to invest now, we will save money by having better, robust service so we get ridership back,” Eng said.

Jim Evers, president of the Carmen’s union, said “The MBTA is a world class transit agency, it just needs to be reminded that it is.”