A new national report advocates tearing down ten aging highways in order to improve cities across the United States. Released by the nonprofit Congress for the New Urbanism (CNU), the report Freeways Without Futures 2017—now in its fifth edition—says that removing highways would fight pollution, ease traffic, and improve walkability and health.

Much of the U.S.’s 200,000 miles of freeways and bridges are falling apart. The most recent Infrastructure Report Card from the American Society of Civil Engineers, for example, said the country would need to spend $3.6 trillion to repair our country’s crumbling roads, rails, pipes, power grids.

From alternative highway designs to making cities safer for pedestrians, the future of urban planning is very much in flux. Central to the problem is how to fix aging interstates. Some cities are reclaiming elevated highways by renovating their underpasses into art installations and parks. But organizations like CNU want to go even further and remove the highways entirely.

Tearing down highways isn’t as crazy at it sounds. Research from cities like San Francisco has shown that demolishing elevated freeways can have positive effects on development without negative effects on transportation.

For many city planners, replacing highways with helps reconnect neighborhoods, decrease our dependence on cars, and reverse urban blight. CNU has identified 10 different highways—from California to New York—as candidates for teardown based on their detrimental impact, the possible benefits of removal, and the political feasibility of each project.

Scajaquada Expressway in Buffalo, New York

Scajaquada Expressway ramps to and from the I-190. #urbanphotography #urbanexploration #landscapephotography #wny #716 #buffalony #wny #landscapephotography A photo posted by Chuck Maley (@chuck_maley) on Jun 24, 2016 at 10:20am PDT

Constructed in the early 1960s, this 3.6-mile four-lane highway carries people in and out of Buffalo, New York, and cuts through the Frederick Law Olmsted-designed Delaware Park.

Community members and the Scajaquada Corridor Coalition want to redesign the parkway to cut noise, decrease pollution, and reduce high-speed traffic. Short-term improvements have already been made: In 2015, the New York State Department of Transportation reduced posted speeds from 50 to 30 miles per hour and reduced lane size.

Construction to transform the expressway into a low-speed urban boulevard is expected to begin this winter, and local community groups are in the process of advocating for more pedestrian and bike-friendly amenities.

I-345 in Dallas, Texas

The Divide #I345 #tearitdown #mydtd #instaDFW A photo posted by Hayden Bernstein (@bernden_p_haystein) on Jun 3, 2015 at 8:36pm PDT

Originally built in 1973, critics of this two-mile elevated highway in Dallas say that the freeway cuts off neighborhoods from downtown and has furthered urban blight. Activists with the organization A New Dallas want to demolish the highway, arguing:

“Blowing up I-345 would free up 245 acres for development that could bring in another 27,540 downtown residents and, based on developable-square-footage estimates, more than 22,550 jobs. … And those estimates are conservative. It would restitch the grid, reconnect Deep Ellum and East Dallas to downtown, and allow the active development happening farther up Central Expressway to move south. … What happens then? Within 15 years, as much as $4 billion in new investment and more than $100 million in yearly property tax revenue.”

The Texas Department of Transportation agreed, releasing a study in 2016 that said demolishing I-345 could be beneficial. Opponents, however, say that a teardown would snarl traffic and overburden city streets. For more on this discussion, head over to the Texas Tribune.

I-70 in Denver, Colorado

The Colorado Department of Transportation has announced a $1.2 billion plan to tear down one of the crumbling viaducts of Denver’s Interstate 70, bury part of the highway, add four more lanes, and expand toll lanes, shoulders, and service roads.

The plan sparked debate among locals because of the highway’s location in three urban neighborhoods: Elyria, Swansea, and Globeville. A group called Unite North Metro Denver has countered the city with a different plan: Reroute interstate traffic to the north and redesign I-70 as a bike- and pedestrian-friendly boulevard.

Proponents of a teardown argue that a boulevard would cut noise and air pollution and bring new investment opportunity to neglected neighborhoods. Folks on the other side of the aisle believe that I-70 is too important to tear down: The highway functions as the regional connection to Denver International Airport and carries upwards of 200,000 vehicles per day.

I-375 in Detroit, Michigan

CNU admits that demolishing a highway in a city built largely by and for the automobile industry may seem unlikely.

But advocates of tearing down Interstate 372—a four-lane, below-ground spur constructed in 1959—point to Detroit’s declining population as a catalyst for removal. Annual daily trips on I-375 have decreased and proponents believe that replacing the highway with a boulevard can reunite Detroit’s Riverfront, Greektown, Eastern Market, and Stadium districts.

According to the Freeways Without Futures study, a lack of consensus and funding questions has put the potential removal of I-375 on hold. The city of Detroit is still open to the idea, however, especially given the continued revival of downtown Detroit. For more on the I-375, head over to Curbed Detroit.

I-980 in Oakland, California

#oakland#i980#hwy24#chillin#illest#telegraph#mlk#nobartinsight#thesimplethingsinlife A photo posted by @jaronbe on Nov 23, 2014 at 6:25pm PST

San Francisco is home to two of North America’s most successful freeway removals: the Embarcadero and Octavia Boulevards. Across the bay, the city of Oakland is considering removing its own highway, a below-grade section of Interstate 980.

Like the other projects cited in CNU’s study, the proposed plan wants to replace I-980 with a surface boulevard that has regional rail service running underneath. The project has gained a lot of support in recent months, including from Oakland Mayor Libby Schaaf.

“Our I-980 is a cautionary tale,” says Schaaf. “It was proposed as a part of a plan to build another Bay Bridge and a shopping mall—but this broken promise leaves us with a scar across our city that separates our residents from opportunity. In its place, we want to reknit our community, building infrastructure that creates local economic opportunity, reconnects neighborhoods, and helps connect the region.”

Route 710 in Pasadena, California

Pasadena’s 710 highway was built in 1964, and, according to Freeways Without Futures, the freeway stub “seized a half-mile swath of Pasadena’s most valuable land, demolishing hundreds of houses to extend the 710 Freeway to the 110 and the 134 and 210 freeways.” A similar stub was built in Alhambra and Los Angeles at the southern end.

Now, the Connecting Pasadena Project wants to fill the freeway stub, convert it to a multi-way boulevard, create a new network of blocks and streets, and use the reclaimed land for new infill development.

Five cities--Glendale, Pasadena, Sierra Madre, South Pasadena, and La Cañada Flintridge—have been fighting over three alternatives proposed by the California Department of Transportation for decades.

Inner Loop in Rochester, New York

Closing up the Inner Loop. #urban #rochester #rochesterny #ROC A photo posted by Josh Lau (@_schlau) on Nov 16, 2016 at 6:30pm PST

After decades of urban flight, downtown Rochester, New York is staging a comeback. According to CNU, businesses and shops are thriving and the city’s downtown population is expected to rise more than 400 percent by 2020.

Some credit the partial removal of the Inner Loop highway—currently in its finishing stages—for the revival. A one mile segment is being filled in and replaced with a walkable, multimodal boulevard surrounded by mixed-use development. The New York Times says that Rochester may be the first city to fill in a below-grade highway.

The success of the Inner Loop’s first removal has inspired further plans. Now, the city wants to fill in the northern section of the Inner Loop and replace it was a surface street.

I-280 Spur in San Francisco, California

When San Francisco tore down two highways in 1989, it was thanks to an earthquake that made repairs costly. Now the City on the Bay is looking to remove a 1.2-mile spur of I-280 and reunite neighborhoods like Mission Bay, Potero Hill, and SoMa.

According to CNU, the removal of the I-280 Spur and its replacement with a surface boulevard has been endorsed by San Francisco Mayor Ed Lee and studied by Bay Area nonprofit SPUR. An urban boulevard could transform former highway land into much needed housing stock and possibly allow space for rail development.

I-81 in Syracuse, New York

Syracuse I-81 #syr#syracuse#cuse#centralny#cny#upstate#newyorkstate#nys#i81#interstate81#81#interstate#traffic#traffictrails#lightrails#downtown#su#syracuseU A photo posted by Tony Shi (@tonyshiphoto) on Nov 19, 2016 at 9:06am PST

The Viaduct—a 1.4 mile stretch of Interstate 81 that bifurcates the city—in Syracuse, New York, is reaching the end of its design life. The New York State Department of Transportation is left with three options: rebuild the elevated highway, replace it with a surface boulevard, or build a $2 billion tunnel across the city.

CNU advocates the boulevard option, arguing that current thru-traffic could be rerouted to I-481 and a teardown would reunite long-separated neighborhoods. According to Freeways Without Futures, NYSDOT is drafting an environmental impact statement identifying the preferred alternative, which is expected to be made public in early 2017.

Route 29 in Trenton, New Jersey

Since the late 1980s, locals in Trenton, New Jersey have called for the removal of Route 29—a highway the separates downtown from the Delaware River waterfront. A plan for removal had momentum in the mid-2000s, but was thwarted by the 2008 recession.

Freeways Without Futures says that removing Route 29—which is once again gaining traction—could allow for a vibrant new waterfront, innovative stormwater management, and a much-needed environmental restoration. Now organized as the Waterfront Reclamation project, advocates say that removing the highway could contribute to $2.25 billion to the city’s economy.