Marin-Sonoma Narrows B-7 Project to Hit Next Milestone as Traffic Shift on US-101 Scheduled for April 11


Schedule: Times, ramp closures to be announced later

MARIN COUNTY — The Marin-Sonoma Narrows B7 construction project continues in April with paving and k-rail adjustment work leading to a traffic shift targeted for April 11 on US-101 in both directions from Novato near Olive Avenue to San Antonio Road.

Southbound traffic will be realigned away from the temporary median lanes, into the newly constructed Southbound US-101 road section. That section has been raised to match the median that was opened back in June 2023.

Northbound US-101 traffic will be realigned into those same temporary median lanes now moving in the opposite direction, as the next phase of construction begins to reconstruct the old northbound road section.

Specific times and dates and nighttime ramp closures will be announced in the coming days.

The new lanes are part of the final phase of a decade-long widening project in Marin and Sonoma counties meant to relieve traffic congestion on the corridor.

All work depends on weather.

Changeable message and directional signs will be in place to assist motorists traveling in the area. The California Highway Patrol (CHP) will be on-site during the closures.

This is the last remaining High Occupancy Vehicle (HOV) lane construction project as part of the 16-mile US-101 Marin-Sonoma Narrows (MSN) program. This project will complete and allow continuous HOV lanes on US-101 from Sausalito in Marin County to Windsor in Sonoma County. HOV lanes are scheduled to be open to use in the summer of 2025.

Construction includes widening US-101 to install HOV lanes for 3.5 miles along the northbound lanes from North Novato to the Marin, Sonoma line, and for 6.3 miles along the southbound lanes from De Long Avenue to the county line.

On June 10, 2023, Caltrans diverted Southbound US-101 traffic onto new elevated lanes spanning San Antonio Creek to just north of Atherton Avenue in Novato. This was the first major milestone for the project.

Please drive with caution. Slow for the Cone Zone and Be Work Zone Alert. Caltrans thanks motorists for their patience while we work to maintain our state's highways, bridges, and tunnels.

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