California Department of Transportation

California Department of Transportation

Date: April 1, 2013
District: 4 - Oakland
Contact: Robert Haus (Caltrans) Seana Gause (SCTA)
Phone: (510) 715-7212 (707) 565-5373


SONOMA COUNTY - Caltrans, the Sonoma County Transportation Authority (SCTA), and the Metropolitan Transportation Commission today celebrated the start of construction on the next phase of the Marin-Sonoma Narrows Project (MSN) on U.S. Highway 101 in Petaluma.

The $700 million MSN Project will widen U.S. 101 from Novato to Petaluma and make other significant improvements.  Known as “The Narrows” for its reduction to just two lanes, this segment of highway has historically experienced heavy congestion.

“This project will bring us closer to our goal of reducing congestion and increasing safety along Highway 101,” said Caltrans Director Malcolm Dougherty.

The MSN projects in Petaluma were allocated $120 million in funding, including $105 million from Proposition 1B, a 2006 voter-approved transportation bond, and $7 million from Measure M, approved by Sonoma County voters in 2004. In total, nearly $15 billion in Proposition 1B funds have been distributed statewide.

The work underway in Petaluma will upgrade U.S. 101 from a highway to a freeway; reconstruct the Petaluma Boulevard South interchange; replace the Petaluma River Bridge; construct or widen nearly three miles of frontage roads; provide new pedestrian and bicycle enhancements; replace the northbound State Route 116 Bridge and widen the southbound SR-116 Bridge to accommodate future carpool lanes on U.S. 101. 

“This work is the foundation for eventual carpool lanes and will bring the highway up to freeway standards,” said Caltrans District 4 Director Bijan Sartipi. “When completed, the highway will be wide enough to accommodate a third lane once the carpool lane projects come through.”
For more information about the U.S. 101 MSN Project, please visit SCTA’s website at or visit the Caltrans District 4 website at 

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