Engineers with the state Department of Transportation said they hope to have the new lanes between Walnut Street and Tryon Road open for motorists by Thanksgiving.
But the highway narrows from four to two lanes north and south of the construction zone, and drivers said they fear new traffic tie-ups near the Interstate 40 interchange -- and on the Interstate 440 Beltline -- and at the split of U.S. 1 and U.S. 64.
"I'm very worried about bottlenecks. I think what the DOT is creating is a situation that's going to help short-term, but it's going to bottleneck long-term," one driver said.
"When it comes Christmas time, it's going to be gridlock. That's a lot of tax dollars spent that didn't get thought through all the way, I think," another driver said.
Jon Nance, the DOT's division engineer for the Triangle, said it's tough to find a good place to stop a road improvement project without causing new congestion, especially in heavily traveled areas like the U.S. 1 corridor.
"The interchange at the Beltline and U.S. 1 is already busy. It was busy before we started; it'll be busy when we finish," Nance said.
Projects that would help the situation, such as widening I-40 from U.S. 1 to Wade Avenue and widening the two-lane sections of the Beltline, are too low on the DOT priority list to receive funding, Nance said. That could change if the projects were built as toll roads, he said.
Still, Nance said that traffic flow will improve through Cary when the new lanes are opened in the coming weeks.