Work to repave U.S. 395 south of Stewart Street and expand it to six lanes will be completed by the first week of September.
Nevada Department of Transportation spokesman Scott Magruder said the section of road is one of the most congested in Carson City with more than 40,000 cars using it each day.
"It's something that will really help alleviate the traffic congestion in the south part of town," he said.
The extra lane will eat up the shoulder and eliminate the bicycle lane, but was made possible because NDOT is overlaying and repairing the road with a new 3-inch layer of pavement and a new surface.
"It made sense because we've got enough right of way," he said.
Magruder said the project will cost about $1.2 million. When completed, there will be three southbound lanes from Stewart Street to Jacks Valley Road and three northbound lanes from Stewart to the junction with Highway 50 to Spooner Summit.
Magruder said NDOT has tried to minimize the impact the work would have on existing traffic congestion in the area by doing it at night. Work hours on the project run from 7 p.m. to 6 a.m.