The state-run MTA may close the L train for a year, or more, for Superstorm Sandy repairs.

The chaos this closure will cause for hundreds of thousands of young workers is a reminder of how much the city depends on subways. Yet in last week’s budget speech, Gov. Andrew Cuomo offered no real way to fix our broken transit system — because what’s really broken is how we pay for transit.

We can barely fit new people on the subways, as the L train crowds from Brooklyn are proving. We built “luxury” apartments instead of building better trains, subjecting people to a miserable quality of life. Last week, Sen. Chuck Schumer called for the feds to pay for new electricity sources so that the MTA can handle 2,200 more passengers on the line every hour (presumably after Sandy repairs are done).

But even if the feds pony up — hey, our next president may be from New York, and sympathetic to supporting “luxury” real estate — they won’t pay the whole thing.

Plus, the rest of the subways, commuter rails, buses, bridges and tunnels need $29 billion every five years in repairs and upgrades to barely keep up with a growing city. The fares you pay don’t cover this cost — they don’t even cover paying the people who run the trains to come to work.

So where to get the money?

Cuomo and Mayor Bill de Blasio said late last year that, don’t worry, they’d find it. To fill the gap left over after the MTA borrows money and Washington sends us their share, the state would put in $8.3 billion over five years, and the city would put in $2.5 billion.

People wondered last year where Cuomo and de Blasio would get this money, and were told to wait till next year.

Well, it’s next year — and the governor’s new budget makes the answer clear.

The grandchildren of the L-train hipsters will pay. Instead of putting in $8.3 billion, Cuomo has reserved only $1.4 billion over five years — a little less than $300 million a year.

Worse: To pay for this, he’s slashing the state’s funding of the City University of New York — by about $500 million a year.

You don’t have to be a genius to see that $300 million a year is less than $500 million a year. So really, the city is getting nothing — or nearly $200 million a year less than nothing — in return for Gothamites’ high tax payments to the state.

How do you make this work?

Simple: You push the costs to the future.

The state — whether through the MTA or some other fancy way — will have to do more borrowing than it planned.

That would be lovely if the future didn’t have its own need for money. But inconveniently, in another five years, the MTA is going to need another $29 billion, because of intense wear and tear on the subway system.

It doesn’t help that Cuomo keeps adding new things for the MTA to do. Earlier this month, he said that he’d build a third track along the Long Island Rail Road. A worthy idea. But that means another billion — at least — in MTA spending.

And remember, Cuomo can only come up with this $1.4 billion because New York City’s economy has done so well since he’s been governor — meaning unexpected budget surpluses from city taxpayers paying their state taxes.

In 2010, when Cuomo won office, the state collected $34.5 billion in personal income taxes. Last year, it took in $45.4 billion. And three years from now, the state expects to haul in $54.9 billion.

But what if it doesn’t? Wall Street, and the global economy, may be crashing right now. But if not now, they will eventually.

That means deficits — and “emergency” tax hikes and spending cuts, just like what happened with the MTA back in 2009, when then-Gov. David Paterson had to enact a new $2 billion-a-year tax package just to keep the buses running.

Despite all of Cuomo’s grand promises, then, there’s no plan — except to wait for a crisis, when we’ll need a plan in a hurry.

Nicole Gelinas is a contributing editor to the Manhattan Institute’s City Journal.