Avg. daily car traffic


Avg. daily truck traffic


Project Length in Miles

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marin sonoma narrows

The Narrows on US Highway 101 (US101) links the San Francisco Bay Area and Oregon and is the only continuous north-south route through Marin and Sonoma counties. Issues with the route include an insufficient number of lanes through the Narrows, sections that do not meet current freeway standards and a consistent poor level of service (e.g., delays, slow traffic, traffic jams) in many sections. This project is included in the 2010 Regional Transportation Plan and the 2002 Key Transportation Corridors in the Bay Area Region. 🙂

Project objectives:

Widen 17 miles of US101 from four to six lanes by adding one high occupancy vehicle (HOV) lane in each direction.

Create a controlled-access freeway section (no traffic signals or intersections) through the historic “Narrows” to improve traffic flow

Upgrade the highway to current freeway standards from Route 37 in Novato (Marin County) to Old Redwood Highway in Petaluma (Sonoma County)

In addition to the carpool lanes, new interchanges and frontage roads are being built to remove unsafe access from private properties and local roads. The project also includes continuous Class I and Class II bikeways between Novato and Petaluma.

For more details, visit the Caltrans website

Fast Forward Drone

MSN Aerial Video - November 2019

Time Lapse Video - San Antonio Creek Area

Bird's Eye View of Marin Narrows

San Antonio Creek Area Construction

Fast Forward Drone