The Nevada Department of Transportation is lining up money for the expansion of a congested 3.7-mile highway interchange in Las Vegas. Currently the busiest section of I-15 in the state, the interchange moves about 250,000 vehicles each day from the Las Vegas Strip through downtown and to the city’s northern suburbs, with the amount of traffic expected to double over the next couple of decades.

The expansion, named Project Neon, will consist of five parts, ranging from building larger ramps to connecting carpool lanes. Depending on how many components are eventually approved and funded, the project could cost anywhere between $600 million and $1.8 billion.

Plans to expand the Spaghetti Bowl, as the interchange is known, come as U.S. cities everywhere struggle to cope with the dual burdens of increased traffic and aging infrastructure. In its 2013 “infrastructure report card,” the American Society of Civil Engineers gave American roads a less-than-stellar grade of D, with urban systems singled out for costing $101 billion annually in wasted time and fuel. The reasons for the lack of funding are complex, but come from a combination of declining federal support for transportation projects and dwindling gas tax receipts as people drive less and purchase more fuel-efficient cars.

Rather than rebuild or expand obsolete highways, some urban leaders have turned to the idea of removing downtown highways and replacing them with boulevards. In places like San Francisco, Niagara Falls and Dallas, planners expect that downtown highway removal would increase pedestrian and cyclist connections, create green space, improve public health and return investment to neglected neighborhoods. They are not without precedent.

Downtown Las Vegas, through which the Spaghetti Bowl runs, fell on hard times after most of the city’s gambling moved a couple of miles south to the more famous Las Vegas Strip. In 2012, Zappos CEO Tony Hsieh announced a $350 million investment to move his company’s headquarters to the area, with the goal of turning downtown into a bustling tech hub à la San Francisco.

Urban highway removal would have the potential to attract the residents and investment that Hsieh is looking for. In a city like Vegas, however, a move like that would face multiple obstacles. For one, there’s Sin City’s car-centered development patterns. Though the Brookings Institution cited Las Vegas as having the eighth best transportation system in the country based on access to employment and coverage, the city earned the spot almost exclusively through buses, which are subject to the same road congestion as drivers.

The region’s spread-out economic activity would also pose and issue, as commuters are split between downtown, the Strip and industries in outlying suburbs. Zappos had a former headquarters in Henderson, Nev.

Whatever route NDOT chooses to take, the region is likely to see more and more cars on its crowded roads in the coming years. Las Vegas is the nation’s 31st largest metro area according to the census, but between 2000 and 2010 it grew by 575,504, or 41.8 percent — making it the fastest-growing in the country.