Why there is always traffic on this Bay Area stretch of I-80

In a twist of highway irony, the construction of the managed lanes will temporarily add to traffic congestion over the next two years as crews convert existing high occupancy vehicle lanes in one section or build out two new lanes in another.

For decades, I-80 in Solano County has forced Bay Area drivers to do something that betrays their inner code: slow down and deal with it.

The big merge

Before I-80, we had America’s longest main street.

The highway is named after Dwight D. Eisenhower, whose administration installed the transcontinental interstate highway system across the country. I-80 was built on top of what was once U.S. Route 40 — nicknamed the “main street of America” — replacing this roadway and designation entirely.

I-80 wraps the country, starting with the Bay Bridge and ending at the George Washington Bridge in New Jersey. As a major artery, the route is fed with multiple other roadways, which is why there’s a frequent flow of travelers. 

Approaching Fairfield from the Bay Area, I-80 connects with two other major roadways: Interstate 680 from the East Bay and state Route 12 from Napa. This interchange is where much of the Bay Area merges into a single roadway all at once. 

“That causes back-ups because of the sheer volume of traffic that went from 3-4 highways merging into one main I-80,” Vince Jacala, a spokesperson for Caltrans District 4, told SFGATE via email. “For example, if you’re driving from Martinez/Concord on I-680 toward Sacramento, you’ll merge onto I-80 in Fairfield. If you’re driving from Napa/American Canyon on Highway 12 (SR-12) to Sacramento, you’ll merge onto I-80 in Fairfield. If you’re driving from Vallejo/San Francisco on I-80 to Sacramento, again, you’ll merge onto I-80 in Fairfield. You get the point. It’s been like that since I was a little kid growing up in Vallejo in the 1970s.”

John Goodwin, spokesperson for the Metropolitan Transportation Commission (MTC), which oversees the Bay Area’s transportation planning, added how the data shows trucking from the Port of Oakland connecting with I-80 from I-680. Adding to the holdup is the I-80 Eastbound Cordelia truck scale just after the interchange.

The addition of freight to regular drivers creates a large number of drivers on the road. “Throughout this whole corridor, the average number of vehicles traveling on any given day is over 100,000,” Goodwin said. “That’s a really big number.”

A population shift

What was once a traffic issue snarling peak commuting hours has become a customary inconvenience that’s been further exacerbated by a population shakeup in recent years as more people moved eastward from San Francisco. As previously reported, the top in-state destination for people leaving the Bay Area was Sacramento.

“During regular M-F weekday commute hours, the morning and evening commutes along I-80 in Solano County seem to be increasing,” Jacala said. “That’s because more people seem to be buying more affordable homes in places like Vallejo, Fairfield, Vacaville and Dixon. Then commuting to either the Bay Area or Sacramento.”

The trend is supported by available traffic data. Transportation analytics firm Inrix shared numbers with SFGATE focused on I-80 between I-680 and Interstate 505 for weekdays from 2019 to 2022. The firm found that eastbound evening traffic has worsened since 2019, adding a 5% increase in travel time.

Caltrans keeps a public traffic count; its data is available as far back as 2013 and as recent as 2020. In viewing the data to compare 2013 and 2020 for the section of I-80 between the I-680 interchange near Fairfield and the I-505 interchange near Vacaville, it’s apparent how there’s been a steady increase over the past decade. 

“The number of vehicles passing through Solano on 80 has increased by anywhere from 2% to 7% in seven years,” Goodwin said. “While this increase may seem modest, depending on your location, 2% to 7% has an impact. It’s helpful to think of freeways like how we think of rivers: It’s about flow. You can have a big rainstorm where 2-3 inches of rain will fall, and the rivers and creeks can accommodate it. But the next day, you get half an inch, and that exceeded the banks and the ability of that conduit.

“The point being that on a conduit as heavily used as I-80 in Solano, it doesn’t take a lot of rainfall for flooding to occur.”

Lane management

The last major widening project for I-80 was in the 1970s, but a group of transportation agencies has begun a lane-expansion initiative that was 17 years in the making. 
 
Caltrans, MTC and the Solano Transportation Authority are collaborating on the I-80 Managed Lanes Project, which will add express lanes to both sides of the highway. Also called managed lanes, these highway aisles are available to carpools and to solo drivers willing to pay a toll that will fluctuate depending on volume. 

The vision is that by 2024, the addition of these managed lanes will incentivize drivers to carpool or choose public transit to bypass the clogged lanes. 

The 18-mile stretch of roadway is split into two projects: converting 8 miles of existing carpool lanes into managed lanes between Cordelia and Air Base Parkway in Fairfield and constructing10 miles of new managed lanes between Air Base Parkway in Fairfield and Leisure Town Road in Vacaville near the I-80/I-580 interchange.

The $228 million construction project broke ground last year and is on course to finish on time. As construction continues, drivers can expect another reason to slow down.

“During the project, motorists must also slow down because all 18 miles are an active construction zone with moveable concrete barriers installed and CHP enforcing 55 MPH through the construction zone,” Jacala said. “This area will also see increased construction activity during this summer as crews pour cement, pave roadways, install overhead gantries and perform multiple traffic lane switches during the work.”

Daryl Halls, executive director for Solano Transportation Authority, told SFGATE how this action plan for the I-80 corridor stemmed from a 2005 study as transportation managers were anticipating population growth.

“In the mid-1990s, there wasn’t the traffic you see now, but MTC projected there would be with future growth, as a lot of folks came out here to live in Solano County because it’s more affordable to live,” he said.

The proposal for adding lanes to highways to solve congestion is often criticized. Goodwin said it’s a fair argument. 

“As a concept, that declaration is not without some validity. But then you have to get into the dynamics for this particular corridor,” he said. “Keep in mind, the work going on for the 80 is to add an express lane in each direction. What’s key is that it’s not so much about moving vehicles through the corridor but moving more people through the corridor more efficiently.”

He said that MTC has seen success in express lanes in other parts of the Bay Area like on Interstate 880.

“The data is very clear that folks are using the lane and using it in greater numbers,” Goodwin said. “The qualifying carpool travels toll-free.” he added. “The solo driver has the choice to pay the toll to take advantage of the travel time viability.”