Skip to main content
You are the owner of this article.
You have permission to edit this article.

Big Highway 12 project underway to end Jameson Canyon backups for Napa motorists

Here’s a sight for congestion-weary eyes — orange-vested construction workers driving piles, bulldozing dirt, and building bridges where Highway 12 meets Interstate 80.

Call them the Jameson Canyon bottleneck-busters.

They are building what is supposed to be the solution to eastbound, mile-long evening Highway 12 backups. While the highway through Jameson Canyon is two lanes in each direction, that drops to one eastbound lane just before the freeway.

A one-lane connector ramp between highway and freeway is the culprit and a two-lane ramp is the planned solution. That will get rid of a much-maligned merge point.

This is a $77 million project in Solano County that should benefit Napa County, given Highway 12 is the main link between Napa County and the Central Valley.


Ashley O’Brien is among those looking forward to the day of completion scheduled for fall 2022. She commutes between her Elk Grove home and Napa job and that backup can add 15 minutes to her trip home.

O’Brien wonders just what exactly is taking shape with a construction project that spreads over a sizable area. Workers are doing far more than slapping down pavement for an additional lane.

“I just kind of pay attention every day I go past it,” O’Brien said. “I’m really interested in what the final (project) is going to look like.”

So is Jennifer Tydingco, who makes the commute from Vacaville to her Napa job. She said the Jameson Canyon bottleneck is the biggest congestion problem on her evening trip home.

“I can’t really envision it yet,” Tydingco said. “I can see there’s stuff going on and they have these signs up. It’s a construction zone. I’m focused on the road.”

What’s to come

On Tuesday, Caltrans officials gave a tour of the construction site and explained what’s to come.

Napa County residents will benefit from this Solano County project designed to end Highway 12/Jameson Canyon backups.

A major focus, of course, is replacing that one-lane connector ramp bridge that curves over I-80. As of Tuesday, the wooden form for the new, wider bridge was taking shape. Expect the new bridge to open this fall and the old bridge to be demolished, Caltrans officials said.

But it will take more work to bust the bottleneck. The area will remain a construction zone for perhaps another year.

Another project component is sorting out the traffic streams heading to eastbound I-80, Green Valley Road, and southbound Interstate 680. They presently crisscross as drivers jockey for position.

“This is a major complaint we have from the traveling public,” Caltrans Resident Engineer Fernando Dos Santos said.

So the connector ramp will split after crossing the freeway, with I-80-bound traffic going one route and Green Valley Road-bound going another. Meanwhile, still another route will carry eastbound I-80 traffic bound for Green Valley Road and southbound Interstate 680.

Separating these traffic streams will mean building a second, smaller bridge.

Still another change is coming within a matter of weeks. Red Top Road ends in a T-intersection at Highway 12 just before the connector ramp. Vehicles turning left or right from Red Top Road onto the highway must squeeze amid the traffic stream.

Tydingco said she’s seen a lot of near-miss accidents.

“That whole section right there is a little dangerous, in my opinion,” she said.

Caltrans will close the Red Top Road entrance onto Highway 12 for safety reasons, though people will still be able to exit the highway onto Red Top Road.

When all is done, eastbound Highway 12 vehicles still might not always flow onto I-80 without a stop. If I-80 has heavy traffic, a metering light will be triggered along the connector ramp, similar to the one that is there today.

The past

The Highway 12 route through Jameson Canyon dates back to the horse-and-buggy days, when it was a dirt road. It provided a link between the then-small towns of Napa and Fairfield.

In 1917, the automobile age had dawned and big changes were coming to the road. The State Highway Commission awarded a $30,000 contract to a Colusa County firm to pave 3.5 miles through Jameson Canyon.

By 2013, Caltrans estimated 33,500 cars daily traveled Highway 12 through Jameson Canyon during peak months. Yet most of the highway still looked like a two-lane country road, albeit one jammed with traffic. Solano County residents working in Napa County used it for their commute.

That congestion fueled a push to expand all of the Jameson Canyon stretch to four lanes. The project was completed in 2014. In 2019, an estimated 46,500 vehicles traveled the road daily during peak traffic seasons, according to Caltrans traffic counts.

However, the ramp from eastbound Highway 12 to eastbound I-80 remained one lane, leading to the merge and the bottleneck. Now the work is underway to put what might seem like a finishing touch on the Highway 12/Jameson Canyon widening.

The big picture

That’s the perspective from Highway 12 in Jameson Canyon. There is also a perspective from I-80, where a series of interchanges for Highway 12, Green Valley Road, I-680, and Suisun Valley Road spread over a mile have caused traffic snarls for decades.

The Highway 12/I-80 connector ramp project underway now is only a piece in a far larger puzzle to ease I-80 congestion problems.

“I’ve got a question for all of you,” Rep. John Garamendi, D-Walnut Grove, said during the virtual groundbreaking for the Highway 12 connector ramp project on Oct. 26, 2020. “What is the single biggest interstate highway project in California?”

The answer, of course, is the effort to cut this Gordian knot of interrelated I-80 traffic tie-ups.

The solution announced in 2012 was to spend about $740 million to reconfigure various interchanges. The package was broken down into seven stand-alone parts.

The first piece, completed in 2017, involved renovating the westbound Highway 12 entrance to Jameson Canyon and relocating the Green Valley Road interchange. This cost about $67 million.

Now comes piece two, the eastbound Highway 12 connector ramp to I-80.

Still to come are such pieces as relocating the I-80 and I-680 interchange and extending Business Center Road in Fairfield’s Green Valley area over the hills to a planned Highway 12 interchange in Jameson Canyon. Money must still be found.

All of these pieces are to someday dovetail in an effort to create highway harmony out of congestion cacophony.

Catch up on Napa County's top news stories

In case you missed it, here is a look at the most-read stories on

You can reach Barry Eberling at 256-2253 or

Get local news delivered to your inbox!

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.

Napa County Reporter

Barry Eberling covers Napa County government, transportation, the environment and general assignments. He has worked for the Napa Valley Register since fall 2014 and previously worked 27 years for the Daily Republic of Fairfield.

Related to this story

Get up-to-the-minute news sent straight to your device.


News Alerts

Breaking News