In his inaugural speech Friday, President Trump promised “a great national effort to rebuild our country.” To that end, he has already floated a plan to spend $550 billion over four years on infrastructure.

And when it comes to spending on roads, transit and airports, nobody in Congress is in favor of small government. That was obvious during the confirmation hearing this month for Trump’s nominee for transportation secretary, Elaine Chao.

A parade of senators asked for everything from new highways through “treacherous terrain” in the Southwest to commuter rail in New Hampshire. “How are we going to pay for all these great ideas?” Chao asked rhetorically, as senator after senator asked her to support each state’s pet project. (And no one was curious about cutting costs.)

But we can get a lot of good infrastructure for less than $550 billion. Even spending half that would give us a great start.

And how to pay is easy: Washington borrows money for solid long-term investments, just like everyone does.

The harder part is to make sure they are good investments. Here are eight good ideas for America’s infrastructure:

Build a rail tunnel under the Hudson River between New York and New Jersey

The existing tunnel is 107 years old. It’s falling apart faster now because of damage from Hurricane Sandy nearly five years ago. But Amtrak can’t shut it down without disrupting rides for 200,000 people daily, most of them New Jersey Transit commuters from New Jersey to New York.

As New Jersey Sen. Cory Booker said at Chao’s hearing, “more people use those tunnels than the entire population of South Dakota every day . . . If these tunnels would go down, they would cost about $100 million in lost productivity every single day.”

Already, commuters are suffering more unpredictability — and lost productivity at work and at home — as Amtrak scrambles to keep up with the deterioration to tracks, signals and electrical wires.

A new tunnel would make life better for Jersey residents and their New York employers and colleagues. But it’s an even bigger interstate project than that. More capacity would mean that Amtrak could offer more service from Washington through New York to Boston, part of a plan eventually to cut travel times among the three cities.

Crucially, too, the tunnel is a project that nobody objects to. For that reason, it’s a better prospect than New York and New Jersey’s other mega-project: a new bus terminal for the commuters who take buses instead of trains. Yes, the Port Authority Bus Terminal is falling apart, too, with its upper floors unable to bear the weight of today’s bigger buses.

But the reality is New York and New Jersey politicians have no clue how and where to build a new bus terminal without hurting the people who live and work in Hell’s Kitchen and without disrupting existing commutes. The two states still need years to show they can take these problems seriously, not money now.

Cost: $20 billion for the tunnel

Have a competition, too, for better commuter rail

From Silicon Valley to Massachusetts, highways are getting more crowded at rush hour, yet almost nobody takes the train to work. As rookie New Hampshire Sen. Maggie Hassan said at Chao’s hearing, even her once-rural state could use commuter-rail investments into Boston as the immediate suburbs become more crowded and expensive.

Let’s have a national contest for new commuter-rail line cash for regions willing to build denser housing — condos, apartments and single houses closer together — around those lines. More commuter rail would take some pressure off high-cost cities, too, as people would have more housing options outside of the metropolises.

Cost: $50 billion

Finish the Second Avenue Subway

New York is finally enjoying the first three stops of the subway, with the first of what will eventually be 200,000 new riders experiencing a faster commute and more time with colleagues or with family (depending on whom you like better). But the subway is supposed to go up through Harlem and, in the other direction, downtown. The state and city haven’t started work, or found most of the money, for the next three stops.

Cost: $8 billion

Launch a competition for train-to-the-plane projects

Only in America can you not take a train from urban centers to the plane — or, at least, do it in under two hours. Gov. Andrew Cuomo wants to build train connections to both JFK and La Guardia but hasn’t said how he’ll pay for them. Boston, too, has a primitive bus system to get you to your plane, and Chicago has only a subway that makes local stops. Getting more businesspeople and tourists on high-quality trains from city centers to airports means less traffic on local roads and highways.

Cost: $15 billion

Build an interstate highway between Las Vegas and Phoenix

As new Nevada Sen. Catherine Cortez Masto, who ran partly on the issue, said at the hearing, these cities “are two of the largest in the country” — just 300 miles apart — “that are not connected by an interstate.” Fixing this would be good for tourism and business and good for public safety, too, as highway travel is much safer than travel on smaller roads.

It would be a good idea, too, to study the idea of building rail along the new interstate, to give people a free-market choice of how to travel. That way, people going from outlying areas of each city could drive, but people going from Phoenix’s increasingly popular downtown to visit Las Vegas wouldn’t need a car for the trip, just like from New York to Boston.

Cost: $10 billion, more with rail

Fix the nation’s subway systems and commuter rails

It’s a good thing it doesn’t snow anymore, because Boston’s subways barely work in a blizzard. Even on a good day, the Red Line, which was once a dream compared to New York’s packed trains, is a disaster of delays and breakdowns. San Francisco passengers, too, are suffering the effects of years’ worth of delayed maintenance.

To ride the DC Metro is to take your life in your hands; nine commuters and nine workers have died in little more than a decade. New York is in better shape but could use more money for normal repair and replacement and for modern signal technology to run more trains closer together, as well. Commuter rails around the country, including in New York, could still benefit from converting rails to electric — a rather proven technology by now — from diesel.

Money, though, should come only with much better accountability for exactly how it is spent and on the results. The feds should compare who does this work most efficiently and reward them over a period of time with more.

Cost: $50 billion

The Wall

Relax, please, if you hate the Wall. And (if you don’t like Trump) stop falling into the trap that helped Trump win. Many Trump voters were sophisticated enough to understand that border security is core national infrastructure.

There is a reason why the US government makes you put your passport in the little slot at JFK when you come home from skiing, before they let you pass through what is, well, the immigration hall’s physical wall: It is generally thought to be a good idea to have some dim notion of who is coming and going.

Border crossings from Mexico and points south are down from a decade ago, in part because of bipartisan efforts and more than $100 billion worth of spending to make it harder. In fact, we already have big chunks of a wall on the Mexican border (really — I saw it!).

But with nearly 200,000 people still making the trek each year, we still face both a security risk and a humanitarian risk.

For all of Trump’s bluster, his proposal is to keep doing what we’ve been doing and do it better: using physical barriers as well as technology to make it even harder (Trump’s voters were also smart enough to realize that a wall can be partly metaphysical). A securer border is good for workers, too: People who have no right to work in this country are the easiest to exploit and endanger, and employers use their presence to push wages down for other low-wage workers.

Cost: at least $20 billion. (And yes, Mexico can pay for at least part. The US government can tax the money that workers here send back home to Mexico. This idea may be good or bad, but it is not, and never was, absurd, as Trump’s opponents often claimed.)

Help states, cities and towns do basic maintenance and management

As we know from Flint, Mich., some states and cities don’t even have the financial resources or competence to guarantee the basic right of safe water. Closer to home, Syracuse, too, has long requested money for water investment.

Poorer areas are in a vicious circle: If you can’t deliver water, keep the streetlights on and fill in potholes, you’ll lose even more residents. The feds should offer grants and zero-interest loans for particularly distressed areas, coupled with outside management expertise to help them relearn the basics.

For middle-class and wealthier areas, the feds could offer smaller grants and slightly higher interest-rate loans to do the basic work of filling in the cracks in the roads. Some of these boring but vital projects are expensive, too: New York will need close to $2 billion to keep the Brooklyn-Queens Expressway from falling down.

Cost: $50 billion

Nicole Gelinas is a senior fellow at the Manhattan Institute. Twitter: @nicolegelinas