It's the road everyone in the North Bay loves to hate. If you’re checking highway 37 traffic right now, you’re likely sitting in a line of brake lights stretching from Sears Point toward Vallejo, or maybe you're just smart enough to check the status before leaving the house.
Honestly? It's a mess.
Today, Sunday, January 18, 2026, the situation is a mix of the usual Sunday afternoon "everyone going home from Napa" crawl and some persistent weather issues. Caltrans issued a dense fog advisory earlier this morning for the stretch between Sears Point in Sonoma County and the I-80 junction in Solano County. While the sun is trying to poke through, that heavy "tule fog" lingers over the marshes, dropping visibility to almost nothing in the low spots.
The Real Reason Highway 37 Traffic Right Now is So Bad
People call it the "Blood Alley" for a reason. It’s not just the narrow lanes or the lack of a median for long stretches; it's the fact that the road is literally sinking. We’re dealing with a highway built on a 19th-century levee.
Right now, if you're heading Eastbound toward Vallejo, you'll hit that infamous bottleneck where two lanes suddenly become one. It’s a design flaw that has frustrated commuters for decades. As of mid-day today, speeds are averaging about 15-20 mph through the "narrow" section. If you're coming from Marin, expect a 25-minute delay just to get past the 121 interchange.
Construction and Maintenance Alerts
Wait, there’s more.
- Marin County Maintenance: Caltrans has been out this week between Atherton Avenue and the Petaluma River Bridge. They are doing "Capital Preventive Maintenance."
- What that means for you: They've been installing concrete barriers and shifting K-rails. Even when they aren't actively working, the lane shifts cause people to slam on their brakes.
- Bridge Work: There were scheduled lane closures on the nearby Carquinez and Benicia bridges recently. When those bridges backup, people try to "shortcut" through Highway 37, which just makes the gridlock over the marshes even worse.
Is it Flooding?
Not today. But it’s always on our minds.
We remember January 2023 when Novato Creek overtopped the levee and shut the whole thing down for four days. Thankfully, even with the recent rains, the road is currently dry. However, with the high tides we've seen this week, the "Manzanita Park and Ride" lot in Mill Valley—a common meetup spot for 37 commuters—has seen partial closures of its lower half due to flood warnings.
If you are parked there, move your car.
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The $500 Million Fix (Finally)
If you’re fed up with highway 37 traffic right now, there is actually some light at the end of the tunnel. Or the causeway, rather.
Governor Newsom recently signed Assembly Bill 697. This is a huge deal. It clears the legal hurdles for the "Sears Point-to-Mare Island Improvement Project."
Basically, they are going to spend roughly $500 million to widen a 10-mile stretch of the road. No more merging into a single lane in the middle of a marsh. They’re also planning a tolled eastbound lane to help pay for it. Construction on the first phase is slated to start later this year (late 2026).
It’s not just about adding lanes, though. The "Resilient 37" partnership is trying to figure out how to raise the entire 21-mile corridor onto a bridge-like structure. If they don't, experts from the Metropolitan Transportation Commission (MTC) say the road will be underwater permanently by 2050 due to sea-level rise.
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Better Ways to Get Around Today
Look, sometimes the best way to handle highway 37 traffic right now is to just not be on Highway 37.
- The Highway 12/121 Alternative: It takes you through the Carneros wine region. It’s beautiful, but honestly? On a Sunday afternoon, it’s often just as backed up with wine tasters.
- Richmond-San Rafael Bridge (I-580): If you’re trying to get from San Rafael to the East Bay, this is usually faster, but keep in mind Caltrans has been doing overnight lane closures on the westbound side there too.
- Check the "Sears Point" Camera: Before you commit to the marsh, look at the live Caltrans QuickMap. If you see a solid red line from Lakeville Highway to Mare Island, take the long way around through American Canyon. It’s an extra 15 miles, but you’ll keep moving.
Current Incident Report
As of 1:15 PM today, there are no major accidents reported on SR-37, but there is a "Traffic Hazard" report near the Mare Island exit involving debris in the slow lane. CHP is en route.
If you’re driving, watch out for the "rubbernecking" slowdowns. People love to look at the birds in the San Pablo Baylands, which is great for birdwatching, but terrible for the person driving behind you.
Actionable Tips for Your Drive
If you absolutely have to be on the road:
- Turn on your headlights: Even if it’s bright out, the salt spray and lingering fog over the bridges make cars disappear.
- Fill the tank in Novato or Vallejo: There is nothing—and I mean nothing—between Sears Point and Mare Island. If you run out of gas or your EV dies in the single-lane section, you are going to be the most hated person in the North Bay for about three hours.
- Sync your maps: Use an app that has crowdsourced data (like Waze or Google Maps). Highway 37 changes fast. An accident at the Petaluma River Bridge can turn a 20-minute drive into a two-hour ordeal in less than ten minutes.
You've got this. Just stay patient, keep your distance from the bumper in front of you, and remember that by 2029, we might actually have a four-lane road that doesn't sink every time it rains.
Next Steps for Your Commute:
Check the live Caltrans QuickMap or call 5-1-1 for the most immediate updates on any sudden lane closures or accidents before you hit the Sears Point interchange. If visibility is still low, consider delaying your trip until the afternoon sun fully clears the marsh fog.