LAS VEGAS — Transportation officials are bracing for major traffic tie-ups when a widening project closes ramps around the state's busiest freeway interchange in downtown Las Vegas beginning late Wednesday.

Ramps connecting Interstate 15 in both directions to northbound U.S. Highway 95 will be closed by Friday for the next four months in what traffic planners have ominously dubbed "Car-nado."

Nevada Department of Transportation spokesman Tony Illia told the Las Vegas Review-Journal the improvements are desperately needed.

"Ultimately, we ask for southern Nevadans' patience, cooperation and understanding while making these crucial improvements," he said. "The sacrifice will be worth the reward."

It's all part of a $1 billion project to smooth traffic flow through the city's congested Spaghetti Bowl interchange, a chokepoint on Interstate 15 that links Los Angeles with Salt Lake City.

The latest segment of Project Neon will also close I-15 ramps to Martin Luther King Boulevard until late February, according to the Transportation Department.

When complete Project Neon will widen 3.7 miles of Interstate 15 in downtown Las Vegas around the Spaghetti Bowl, the busiest stretch of highway in Nevada which sees 300,000 vehicles daily, about one-tenth of the state's population. Planners forecast traffic through the I-15 corridor will double by 2035.

Transportation officials, who have designated several detours, are urging motorist to use alternate routes and apps to help them navigate around the project.

More closures are planned for 2017 and 2018, with work expected to wrap up in 2019 after nearly two decades since the largest public works project in Nevada history was conceived.

When complete, the widening project will add special HOV lanes and flyovers and realign and reconstruct interchanges in the downtown area.

This story has been corrected to show the name of the repair project is Project Neon, not NEON.