In a narrow swath along Manhattan’s Hudson River, stone walls and beautiful arched bridges set off with trees disguise a buried railroad and entwine a six-lane highway.

This is Riverside Park, and it’s an infrastructure masterpiece.

Congress and President Obama shouldn’t commit themselves to spending billions for “shovel-ready” infrastructure projects before examining every inch of the park, which was built during the Depression.

Regrettably, we can’t create its contemporary equivalent today. Great ossified bureaucracies make it all but impossible to unite highways, rails, transit and appealing walkways.

I fear that “shovel ready” means boondoggles like the E- 470 beltway, a six-lane, 46-mile arc through empty high-desert grasslands dotted with new subdivisions east of Denver. Cars cruise the wide-open toll road at 80 miles per hour.

Touted as essential to the metro area’s growth, this land developers’ delight hasn’t lightened loads on more centrally located highways. It’s just rearranged growth patterns, scattering splotches of development over an unimaginably large landscape. New residents depend on long beltway commutes by car.

We can’t do better now, the lobbying legions say, we need to start the bulldozers fast. Translation: No bridge to nowhere will be left behind.

What’s wrong with America’s way of building transportation has long been known. We segregate roads, mass transit, railways and air. Each has its own pot of money. It’s no one’s job to assemble a transportation system that offers the right travel mode for the task at hand.

Aside from the odious earmarks, most transportation funding decisions are made by Metropolitan Planning Organizations. Never heard of MPOs? They’re supposed to set priorities based on real needs, though instead they operate in obscurity and allow the political horse-trading to go on unimpeded by real oversight.

So much is made of the nation’s neglect of infrastructure, yet the U.S. actually is spending record sums on it.

We don’t make progress because the nation fails to lay out new communities so they can be efficiently served by means other than the auto. A start would be to group people-intensive colleges and commercial centers as hubs along corridors served by transit and walkable streets.

While the bureaucracies (state and federal) get overhauled, officials can easily cross off much on the wish lists, like all those beltways that are really land-development schemes posing as congestion relief. (Charlotte, North Carolina, killed an outer- beltway plan some years ago and has done fine, thank you.)

Next, knock out the fourth, fifth and sixth expressway lanes. When roads get that big, there’s enough demand to support high-quality transit. The six rail tracks that tunnel into New York’s Penn Station haul as many people as 45 freeway lanes.

What should Obama support? Lots of innovation has been trickling up from municipalities. Beltway suburbs like Bellevue, Washington, turned their parking-lot acres into high-value suburban downtowns. Focused on transit, they’re appealing as places to walk, shop, work and live.

Some metro areas are aligning roads and rails (both freight and passenger) in corridors to support these emerging urban hubs. The San Francisco Bay Area could use some cash to finally finish a rapid-transit extension linking Oakland and the East Bay to San Jose and Silicon Valley. Without additional aid, underfunded and overburdened big cities will soon have to stop long-planned, often-deferred projects like New York’s Second Avenue Subway.

Express bus lanes and bikeways sharing “green streets” with cars can reduce auto dependency. In the best cases, each mode is physically separated from the others by planted buffers. These little Riverside Parks aren’t just pretty. They make pedestrian crossings safer and sop up storm water — essential in an increasingly flood-prone era.

Dollars spent that get Americans out of cars will ease traffic, save money, reduce pollution, slow global warming and make us less vulnerable to volatile oil oligarchs.

Road projects do little more than rearrange the traffic jams. Look for freeway spectaculars among the proposals, like the 23-lane extravaganza touted for Atlanta’s suburbs. Mark them “D” — for delusional.

James Russell