Nightly Ramp Closures Set For This Week: Marin Sonoma Narrows Project

NORTH BAY, CA — The Marin-Sonoma Narrows B-7 construction project continues this week as Caltrans crews replace ramp lights, requiring closures on southbound U.S. Highway 101 near Novato.

The Atherton Avenue on- and off-ramps on southbound US-101 are scheduled to be closed nightly from 10 p.m. to 6 a.m. Tuesday through Friday.

The De Long Avenue on-ramp on southbound US-101 is scheduled to be closed nightly from 10 p.m. to 6 a.m. Tuesday through Friday.

Detour for Atherton Avenue freeway ramps:

• For the on-ramp closure, drivers should use southbound Redwood Boulevard and enter southbound US-101 at De Long Avenue.
• For the off-ramp closure, drivers should exit at De Long Avenue, turn right, and use Redwood Boulevard.

Detour for De Long Avenue freeway ramp:

• Drivers should enter northbound US-101 at De Long Avenue, exit at the Atherton Avenue off-ramp, and then re-enter southbound US-101.

All work depends on the weather.

Caltrans Reaches Milestone In Marin-Sonoma Narrows HOV Project

The project reached a milestone April 12 when traffic was shifted on US-101 in both directions from Novato near Olive Avenue to San Antonio Road.

Southbound traffic was realigned from temporary median lanes into the newly constructed southbound US-101 road section. That section was raised to match the median, which was opened in June 2023. Northbound US-101 traffic was realigned into those same temporary median lanes, which are now moving in the opposite direction as the next phase of construction begins during which Caltrans will reconstruct the old northbound road section.

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

Motorists are asked to drive with caution during this last remaining High Occupancy Vehicle —HOV— lane construction project of the US-101 Marin-Sonoma Narrows project. The 16-mile MSN project will complete and allow continuous HOV lanes on US-101 from Sausalito in Marin County to Windsor in Sonoma County, with the HOV lanes scheduled to be open for use in the summer of 2025.