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Ramp, Lane Closures on Northbound, Southbound US-101 as Part of Marin Sonoma Narrows B7 Project in Marin County

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Schedule: Monday, May 18 to Wednesday, May 20 from 8:30 p.m. to 6:30 a.m.

Marin County — Caltrans has scheduled ramp and lane closures for erosion control work on Northbound and Southbound US-101 for the Marin Sonoma Narrows B7 project from Monday, May 18 through Wednesday, May 20 from 8:30 p.m. until 6:30 a.m. the next mornings.

Traffic traveling along US 101 where the last remaining High Occupancy Vehicle (HOV) lane construction project will take place as part of the 16-mile US-101 Marin-Sonoma Narrows (MSN) program

The schedule for ramp closures is as follows:

Monday, May 18: The Atherton on- and off-ramps and De Long Avenue on-ramps are scheduled to be closed on Southbound US-101.

Tuesday, May 19: The San Antonio on-ramp on Northbound and Southbound US-101 and the Atherton Avenue on- and off-ramps on both Northbound and Southbound US-101 are scheduled to be closed.

Wednesday, May 20: The San Antonio on-ramps on Northbound and Southbound US-101 are scheduled to be closed.

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 has completed and allows continuous HOV lanes on US-101 from Sausalito in Marin County to Windsor in Sonoma County.

All work is weather dependent.

Detours for San Antonio on-ramp closures on US-101

  • Northbound: Drivers must enter on US-101 southbound at San Antonio Road, exit at the Atherton Avenue off-ramp and then re-enter US-101 northbound.
  • Southbound: Drivers should take Northbound US-101 and exit at Kastania Road, turn left and re-enter Southbound US 101.

Detours for De Long on-ramp closures on US-101

  • Northbound: Drivers should enter Southbound US-101 at De Long Avenue, exit at the Rowland Blvd. off-ramp, turn left, and enter Northbound US-101.
  • Southbound: Drivers should travel Southbound on Redwood Boulevard and enter Southbound US-101 at Rowland Boulevard.

Detours for Atherton Avenue on-ramp closures on US-101

  • Northbound: Drivers should travel south on Redwood Boulevard and enter Northbound US-101 at De Long Avenue
  • Southbound: Drivers should travel Southbound on Redwood Boulevard and enter US-101 at De Long Avenue

Detours for Atherton Avenue off-ramp closures on US-101

  • Northbound: Drivers should exit at San Antonio, turn left, and enter Southbound US-101 to get to the Atherton off-ramp.
  • Southbound: Drivers should exit at De Long Avenue, turn right and use Redwood Boulevard.

For 24/7 traffic updates, please visit 511.org: https://x.com/511SFBay
For real-time information, visit Caltrans QuickMap: https://quickmap.dot.ca.gov
Follow us on X: https://x.com/CaltransD4
Or call 1-800-472-7623, 1-800-427-ROAD for state highway conditions statewide.