The MTA will invest $51.5 billion, which would amount to the largest amount in the agency’s history, to improve New York’s transportation system with a focus on the city’s subway, according to its 2020-2024 capital plan, which was released on Monday.

The subway system (including the Staten Island Railway) will take the largest chunk of that investment with $37.3 billion dedicated to signal modernization along six subway lines, bringing in 1,900 new subway cars, making 70 stations ADA-accessible, replacing tracks, and revamping 175 stations (including elevator and escalator replacements).

“These proposed investments in our subways and buses have delivered beyond my wildest expectations,” New York City Transit President Andy Byford, said in a statement.

Though Byford’s plan to overhaul the subway system, Fast Forward, is not specifically named in the presentation the MTA released today, several of the agency’s priorities align with the cornerstones of that plan, including a modernized signal system and accessible stations.

Advocates who have long fought for a more accessible subway system cautiously celebrated the plan’s focus on improving the lives of New Yorkers who rely on elevators and other access-providing measures.

“Years from now, we may look back at the 2020-2024 MTA Capital Program as the moment when the MTA turned a corner on subway accessibility,” Colin Wright, a spokesperson for TransitCenter, said in a statement. “But a reliable, accessible system won’t happen without strong oversight, accountability, and transparency. We pledge to keep fighting alongside our partners in the disability community until everyone in New York City has equal access to our subway system.”

The plan also includes the second phase of the Second Avenue Subway, which will get its final installment to build three new fully accessible stations and a new connection to the MetroNorth.

Meanwhile, NYC Transit and MTA buses will get a $3.5 billion investment to replace more than 2,200 buses and add more than 175 ones to the system, improve bus depots, and add on-board digital information screens in buses. MetroNorth will get a $4.7 billion investment to reconstruct the Grand Central Terminal train shed and the Park Avenue tunnel and viaduct; advance New Haven Line access to Penn Station with four new stations in the Bronx; and begin to replace the MetroNorth’s M3 rail cars. The Long Island Rail Road will get a $5.7 billion investment to improve signals and communications, improve stations, and upgrade tracks.

MTA Bridges and tunnels will also get a large investment, $3.3 billion, dedicated to fixing several bridges and create the infrastructure needed for central business district tolling or congestion pricing.

How will the MTA afford all of this? A large part of the funds, $25 billion, will come from new sources of revenue including congestion pricing and the progressive mansion tax, but the rest will come from federal funds, the state and the city, and MTA Bonds.

“The draft plan released today is a big step in the right direction: it’s ambitious in scope and it tackles the big problems like modernizing signal technology and making more subway stations accessible,” John Raskin of the Riders Alliance said in a statement. “If all of this work happens as proposed, the transit system will truly be on the road to repair.”

But, Raskin said, “[Gov. Andrew Cuomo] will have to lay out a detailed timeline for the work and manage his MTA to stay on time and on budget. The governor will also have to find the funding required to do the complete job without taking shortcuts or forcing the MTA into more debt. The legislature will have to cooperate to fund these much-needed transit repairs, as well as to ensure that the capital plan is fully vetted and approved and that the MTA is accountable to the public for the money we are investing.”

Cuomo, meanwhile, said that $25 billion has been earmarked by the state legislature for the plan, and that he’ll support an additional $3 billion investment, to be matched by New York City, for the plan.

“We have an historic opportunity to institutionalize the lessons learned, build on the progress made under the Subway Action Plan and make crucial upgrades so riders get the 21st century transit system they deserve,” Cuomo said in a statement.

The plan will now need to be approved by the authority’s board and then submitted to the Capital Program Review Board by October 1.