Drivers dread it, but some can’t avoid it.

The intersection at Highways 121 and 116 in Schellville has been a traffic congestion nightmare for both visitors and residents of Sonoma and Napa. However, motorists have few alternatives when trying to pass through that part of Wine Country.

“There’s no back way, unless you cut through a (gated area) or a vineyard,” said Alan Wastell, tasting room manager at Anaba Wines, at the northwest corner of problematic highway intersection. On busy days, “it can back up for miles,” Wastell said.

State and local officials have been looking for a remedy.

They’re moving ahead with plans that call for a possible two-lane roundabout or traffic signal at the intersection, which is now a four-way stop. However, motorists will have to wait several more years to see any relief.

“We’re at the halfway point” of studies and planning, said Seana Gause, senior programming and project analyst with the Sonoma County Transportation Authority.

Officials are still assessing environmental and other impacts, such as a noise, for both options before they can move ahead with designs, she said. They’re also meeting with business and vineyard owners, who could see some encroachment if a roundabout is built.

“If all the stars align, we would probably be ready to go to construction in five years,” Gause said.

The intersection handles traffic from the two-lane Bonneau Road to the west, and Highways 116 to the north and 121 from both the east and south. While many of the commuters are tourists, Gause said many local residents use it. It’s an important east-west thoroughfare for Napa and Sonoma counties.

Caltrans found 18,000 vehicles traveled daily on that segment of Highway 121 last year, while 15,500 traveled daily on Highway 116.

It also found that the intersection had a “higher than average” accident rate. There were 13 accidents on Highway 116 between April 2008 to the end of March 2011, according to the latest figures provided by Caltrans. Up to a third of them were related to congestion.

During the same period, Caltrans said there were 19 accidents, one of which was fatal, on Highway 121. About half of those incidents were related to congestion in the area, according to the state agency.

Wastell, a Sonoma resident, travels the same roads to get to and from work. He said congestion gets worse around the holidays and weekends when tourists are visiting Wine Country.

Sonoma city officials also are considering building two roundabouts, including one in front of the historic Plaza. The idea faces opposition from many residents.

Sonoma County Supervisor Susan Gorin said she’s seen some support for a roundabout at the intersection of Highways 121 and 116.

“Almost universally, the folks who have talked to me have supported a roundabout approach,” Gorin said, adding that a roundabout seven miles to the north, on Arnold Drive and Agua Caliente Road, has worked well to ease traffic.

She said it’s taken so long to deal with the crossing at 116 and 121 in part because of the number of government agencies involved.

“Because this particular intersection at Highway 121 and 116 is multi-jurisdictional it’s even more complex to design a new intersection,” Gorin said.

Money also will be a hurdle.

Gorin said it’s unlikely the county’s general fund will be tapped for the project, estimated to cost $17.7 million to $26.5 million.

About $5 million could come from Measure M, the quarter-cent sales tax voters approved back in 2004 for transportation needs and road improvements, Gause said. Work continues to make the project “shovel ready” in case officials find state and federal dollars.

The plans also call for sidewalks up to 10 feet wide, which would accommodate both pedestrians and bicyclists. An existing park-and-ride lot could be relocated and the nearby bridge over Yellow Creek replaced.

John Sweazey, owner of Anaba Wines, said although he doesn’t expect to see any “Michelangelo fountains,” a roundabout would be better aesthetically for the highway intersection. He said it remains to be seen whether it would work in an area that will continue to draw heavy traffic.

“We’re excited about having something happen. People have been waiting for a while,” he said.