The proposal features more than 500 projects, including $427 million for a Green Line vehicle replacement program, $411 million on a new fare collection system, and $401 million for a modernization project at the T’s Quincy bus facility. Of those three, the fare collection system and the bus facility are behind schedule and over budget.

For its safety and repair work, the Massachusetts Bay Transportation Authority has said those efforts are “non-negotiable,” according to a presentation last month. That work includes a long-sought safety system to prevent collisions on the Green Line — also long delayed — Commuter Rail crossing improvements, and additional money for inspections, repairs, and upgrades to the system’s stations and other infrastructure.

Last year, the Federal Transit Administration ordered the T to address widespread safety issues after one of its Red Line cars dragged a man to death in April.

“I’m very pleased to see the emphasis on safety and reliability [in the spending plan],” said Betsy Taylor, the chairperson of the MBTA board, during a March 23 meeting.

The T is soliciting public comment on the proposed spending plan. The public comment period remains open through April 24.

Governor Maura Healey, a Democrat who took office in January, has spelled out a sweeping agenda for transportation, including support for more Commuter Rail and bus service, building the Red-Blue connector, and the South Coast Commuter Rail extension.

“Our current transit challenges should be a call to action,” Healey said last year. “My plan will urgently address the failings at the MBTA, expand rail and buses across our state, and continue to fix our roads and bridges. This will drive economic growth, create good-paying jobs, and support residents and businesses.”

Healey has already picked a new general manager, Phillip Eng, who began at the T Monday morning. Eng, former president of the Long Island Rail Road, has pledged to rebuild riders’ trust in the MBTA.

The state’s largest public transportation system is also vital to the state’s efforts to create more housing, curb greenhouse gas emissions, and sustain its economic competitiveness. Advocates said the state’s continued success will rely on a T that can meet its future needs.

Jim Rooney, the president of the Greater Boston Chamber of Commerce, said the MBTA also plays a critical role in helping the state attract — and keep — workers and businesses.

“We need robust public transportation to be part of our future. And we need it there to sustain the growth of Massachusetts,” Rooney said.

Rooney, a former T administrator who served as an interim general manager in the early 1990s, said local companies compete against others across the country for new workers. Prospective employees, he said, will weigh issues like the quality of schools, housing costs, their likely commute, and the reliability of the MBTA.

“[If you] Google the media coverage of the T, you may get scared away,” Rooney said.

Stacy Thompson, the executive director of LivableStreets Alliance, said the T must balance both near-term safety and maintenance, while also working on expansion.

“Things like expansion and resiliency are not extras, or nice to have. They should be considered core to the viability of the system,” Thompson said.

About 6 percent of the plan — roughly $540 million — is set aside for expansion of the current transit system, according to the proposal. That includes projects like extending the T’s Commuter Rail service into Fall River, New Bedford, and Taunton, and planning for a direct connection between the Red and Blue subway lines.

Jarred Johnson, the executive director of the transportation advocacy group TransitMatters, said if the MBTA fails to invest enough in expansion, it risks losing a chance to make progress on these efforts, he said.

One example is the Red-Blue connector, which would extend the Blue Line to the Charles/MGH station in Boston, he said. Massachusetts General Hospital is building its own expansion near the station, and the connector itself could relieve overcrowding at other T stations, Johnson said.

“If we don’t act soon, we are going to miss out on the opportunity to build that project affordably,” Johnson said.

During a March board meeting, the T reported about $9.2 billion worth of requests for repair work and maintenance. The agency ultimately allocated $956 million in response to those requests.

In response to that report, Taylor, the board’s chairperson, asked T staff to create a list of repair projects the T needs to complete. She asked that the list not include expansion work.

“I believe we cannot have... a more safe and reliable T until we achieve a state of good repair, until we understand what it takes to get [there], and the resources that will do that,” Taylor said.

But Aloisi, the former transportation secretary who is also a TransitMatters board member, said the state needs to provide more resources to the MBTA, which currently uses its operating budget to pay down its debt and help fund part of the proposed capital improvement plan.

He argued that the Legislature could improve the T’s financial situation by taking steps like shifting a large share of the T’s debt over to the state, as well as having the state budget take on the cost of the RIDE paratransit service.

“You would be freeing up several hundred million dollars at the T. That would be a relief valve,” Aloisi said.

The T’s financial woes are expected to continue, as officials predict it will have an operating budget shortfall next year, Aloisi said. Devoting more resources to the T, and embarking on a more ambitious expansion plan, would have long-lasting impacts for the state.

Aloisi said the T must invest in making the transit system less expensive to operate and more environmentally friendly. And, perhaps more importantly, it needs to build a service that encourages more riders to use it.

“The benefits of doing that — to everybody in the Commonwealth — are tremendous,” Aloisi said.

Taylor Dolven of the Globe staff contributed to this report.