The MTA has approved its historic $51.5 billion capital spending proposal for 2020-2024. Board members in attendance Wednesday voted unanimously.

The plan marks a 70 percent increase over the transit agency's previous four-year plan, and its largest one ever by far, as part of an aggressive effort to repair the agency's aging infrastructure and accelerate service enhancements for the millions of New Yorkers who use its public transit system on a daily basis.

The MTA said that its plan includes more than $40 billion for NYC Transit, $15 billion of which will come from congestion pricing. It has earmarked $7 billion of that to resignal 11 subway lines, starting with the often delay-plagued Lexington Avenue line, and $6.1 billion to add 1,900 new subway cars -- with the goal of easing delays by 10 percent.

Among the other key components:

Full funding for Phase II of the Second Avenue subway project, which will add three new subway stations in East Harlem to connect to the three Q train stations that opened in 2017 on the Upper East Side. Phase II, when completed, is expected to serve 300,000 people per day. It will also include a new connection with Metro-North Railroad.

A combined $11.9 billion will go to subway station improvements, track upgrades and station accessibility (70 more stations would be made accessible in accordance with the Americans With Disabilities Act, meaning more escalators, ramps and elevators).

About $7 billion will go to new city buses, depot improvements and customer experience upgrades, while $2.5 billion would help the MTA replace its oldest buses and add nearly 200 more to its fleet. The hope is for the MTA to acquire only electric buses starting in 2029.

Also in the interest of serving its customers, the MTA said the capital plan aims to have East Side Access, which will extend Long Island Rail Road service to the east side of Manhattan via Grand Central Terminal, open in 2022. The LIRR expansion effort also includes creating 9.8 miles of a new third track from Floral Park to Hicksville, which will reduce congestion along the railroad's busy Main Line corridor. The third track project also includes station upgrades and the shuttering of dangerous grade crossings; it's expected to open in 2022 as well. Together, the two projects are expected to increase LIRR capacity by 50 percent.

Metro-North Railroad will get another $4.7 billion, which will advance New Haven line access to Penn Station via four new stations in the Bronx. Bridges will also get key upgrades and the Queens-Midtown and Hugh L. Carey tunnels will get $58 million for improved ventilation and safety.

The single largest source of funds for the plan – $25 billion – comes from bonds backed by new revenue streams authorized in this year's state budget, including $15 billion from central business district tolling that was passed by the legislature and signed into law in April by Gov. Cuomo as part of the state's FY 2020 budget. The MTA expects to get $10.68 billion from federal funding programs. Another $10 billion will come from bonds backed by newly established revenue sources dedicated to public transportation: a progressive tax on high-end real estate sales and the elimination of the internet tax advantage. The state has pledged $3 billion, subject to approval by the legislature. Mayor de Blasio said Wednesday, just before the vote, that he would kick in $3 billion in city funds if the MTA promises not to use that cash until it has spent the congestion pricing revenue. He also wants the agency to put unspecified city priorities first.

The remaining $9.8 billion will come from the MTA in the form of pay-as-you-go capital contributions and bonds backed by longstanding dedicated taxes, fares and existing toll revenue.

"This proposed 2020-2024 Capital Program – the most ambitious capital plan in the agency's history – builds on the success of the Subway Action Plan, and with new tools such as DesignBuild and the reorganization that is underway we're certain we can deliver for our customers," Patrick Foye, MTA chairman and CEO, said in a statement. "This plan expands service, increases reliability, speeds up the system, and delivers the world's largest ever investment in accessibility, for both NYC Transit and the MTA's commuter railroads, and at the end of this five-year period, New Yorkers will see a revitalized and modern system for the 21st century and beyond."

A spokesman for the city stressed that the new fixes and changes are welcome, so long as the spending is responsible and actively helps New Yorkers have timely commutes.

"It is imperative that the subways run on the time," said spokesman Seth Stein. "We are reviewing this plan to ensure that it helps get New Yorkers moving and that taxpayer dollars are used responsibly."