If you’ve driven on State Route 37, you likely know how regularly the Bay Area commuter throughway experiences major traffic backup. Now, the State of California plans to revamp the Highway 37 corridor through projects expected to cost over a quarter-billion dollars.

37 is the North Bay’s most heavily-trafficked highway in the east/west direction, leading not only to major and significant delays, but also occasional flooding during winter storms. People take the 21-mile route to work, but tourists from San Francisco also use it to get to wine country in Napa and Sonoma Counties. Four Transportation Back in December 2015, traffic authorities in three North Bay counties (Sonoma, Napa, and Solano) signed a Memorandum of Understanding aiming to address issues the highway will soon face, and now there are new plans to move forward.

As Caltrans explains, the rebuild is in its earliest planning stages, and construction work wouldn’t start for several years, if not longer. However, the State feels it’s crucial to either rebuild or reroute the road to avoid a projected rise in sea level that would cause significant flooding by 2040 and entirely sink the street by 2050.

Photo: California Department of Transportation • Caltrans

Because the route goes over protected and important marshland, environmental studies into improvement projects have to take into account the sensitive ecosystem’s needs along with the goal of finding solutions to future traffic patterns and flooding.

There has been some work already to try to protect the road, which goes through the San Pablo Bay, one of the biggest remaining tidal marshes in the Bay Area. For the past 30+ years, agencies with both the federal and state government have partnered up with environmental conservation non-profits to restore the habitat.

“Caltrans has looked at over 120 miles of preliminary alignments for evaluation in the planning and linkages study,” the Agency says.

The Sears Point to Mare Island Improvement Project gives a couple options for the portion of 10.4-mile SR 37 that spans between Sonoma and Solano Counties. In that stretch, the highway narrows to one lane in each direction, creating a traffic bottleneck. The Improvement Project has several Alternatives for cross-sections. The first is to incorporate a reversible lane, so that peak periods could have two lanes going one direction and one in the other to account for extra traffic headed in a single direction. That could cost about $256 million up front, plus $2 million each year for maintenance and staffing.

The second Alternative proposes incorporating a new lane but also adding a fixed median. The extra lane would be chosen for either the eastbound or westbound lane based on peak commute times, and would cost around $306 million.

Other proposals are to either have two lanes in each direction with a reduced shoulder width, or four total lanes with regular shoulder width. Those would round up a bill between $325 million and $415 million.

Other ideas shift away from simply adding new lanes. Some believe the best option is to elevate the highway or to build a new levee system. There are also some concept designs to re-route the highway further north.

Some propose a bridge across the San Pablo Bay with a separate bike lane and pedestrian pathway. With that notion, the State would want to add in transit options like bus routes, or work-arounds for ferries and trains.

Top image: Sonoma County Transportation Authority