Major fixes for addressing traffic, sea level rise on Highway 37 identified

The first projects, which officials say are about seven years away, will be aimed at reducing traffic along the congested corridor.|

Imagine driving along a four-lane elevated causeway above the brackish San Pablo Bay, shaving more than an hour off the normal Highway 37 commute.

Transportation planners have for years envisioned remaking the 20-mile route from Novato to Vallejo into the North Bay’s most important east-west corridor. Now, they are ready to act.

Officials in Marin, Sonoma, Napa and Solano counties have been meeting for several years, pondering solutions to Highway 37’s notorious bottlenecks, where 45,000 cars per day stretch the normal 20-minute commute to as much as 100 minutes. They have also acknowledged that traffic improvements will be irrelevant without addressing sea level rise - without action, the highway will be underwater in 30 years.

The first fixes will be completed within the next seven years, officials say, and a new formal partnership defines the roles various agencies will play and sets the process in motion.

Branded as Resilient State Route 37, the program that includes the transportation agencies of the four counties plus Caltrans and the Bay Area Toll Authority, is planning vast changes to the highway. The Sonoma County Transportation Authority signed onto the partnership on Monday.

“We’re trying to move into the next phase,” said Supervisor David Rabbitt, an SCTA board member. “I think the pace will pick up going forward.”

During the preliminary work, the study group broke the route into three distinct segments: the four-lane flood-prone stretch from Highway 101 to Sears Point; the narrow two-lane stretch from Sears Point to Mare Island that is plagued with congestion and also susceptible to sea level rise; and the four lanes from Mare Island to Highway 80, with bottlenecks and outdated interchanges.

The middle segment, from Sears Point to Mare Island, was identified as the top priority. Fixes are already in the works to temporarily relieve traffic, although officials say the final solution, which could drastically alter the route’s alignment, is still decades away and could cost several billion dollars.

In the meantime, officials are using $100 million in expected new Bay Area bridge toll money to design the first projects. According to planning documents, the first construction project will be a new roundabout to replace the current traffic signal at Highway 37 and Highway 121 near Sonoma Raceway. The $30 million project should take seven years to complete, according to the documents.

At the same time, another project could expand the capacity of the current two-lane segment from Sears Point to Mare Island by adding a flexible third lane during peak commute times. Using the existing right of way, the extra lane could be added with either a movable median barrier, like the one on the Golden Gate Bridge, or a shoulder running lane, like the expandable third lane on the Richmond-San Rafael Bridge.

Those improvements are expected to cost as much as $150 million and be completed by the end of 2025, the planning documents estimate.

“A couple of interim projects will alleviate the pain,” Rabbitt said. “We’d like to move forward with those.”

The ultimate solution, which accounts for sea level rise, includes some radical concepts and is not planned to start until at least 2040. Plans range from raising the existing roadway onto a combination of embankments and causeways to drastically shifting the route inland so that it parallels an existing rail line. The most revolutionary design would build a straight bridge over San Pablo Day directly from Novato to Vallejo, bypassing the shoreline entirely.

Estimates for those concepts range from $2.4 billion for the causeway along the existing route to $3.3 billion to build a new bridge.

Future plans also call for transit links, including potentially extending SMART train service east to Solano County. Pedestrian and bike paths and wetlands improvements are part of the plan.

The $100 million in funding for the initial phase is currently on hold due to a lawsuit filed by the Howard Jarvis Taxpayers Association, which claims the bridge toll measure voters approved last year was really a tax and needed two thirds of the vote. Officials are still collecting the increased bridge tolls and hope to be able to use the funds if they are successful in court.

For future funding, officials plan to add Highway 37 to the Bay Area Toll Authority’s bridge toll program, which would take an act of the legislature, according to the memorandum the SCTA signed Monday. But even bridge toll money will not be enough to fund all of the necessary improvements, officials acknowledge in the memorandum.

“The parties ... intend to develop a financing and funding plan consisting of other traditional and untraditional funding sources to deliver the program,” the memo said.

(Contact Matt Brown at

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