Night Lane Closures for High Occupancy Vehicle (HOV) Sign Replacement in Marin, Sonoma Counties on US-101 as Part of Marin Sonoma Narrows B-7 Project

Schedule: Marin work scheduled for Aug. 4; Sonoma work scheduled for Aug. 18

Marin County And Sonoma County — Crews are scheduled to switch high-occupancy vehicle (HOV) signs along Northbound and Southbound US-101 in a 52-mile stretch as part of the final steps of the Marin Sonoma Narrows B-7 project this summer. Signs along the corridor are being modified or replaced with signs displaying new uniform carpool hours.

Signs are in the median of US-101, so the far-left lane in both directions of US-101 are scheduled to be closed. Marin County sign replacement is scheduled to begin on Monday, Aug. 4, and Sonoma County sign replacement is slated to start on Monday, Aug. 18. The new signs will be installed prior to the third lane opening in Marin County in late August/early September.

Signs will be switched out between 10 p.m. and 6 a.m. in all directions except for Northbound US-101 in Marin County, which will be between 10 p.m. and 7 a.m.

The new HOV lane hours in both counties will be 5 to 10 a.m. in the mornings and 3 to 7 p.m. in the evenings, Monday through Friday.

The existing HOV hours of operation on US-101 in Marin County for the southbound direction are 6:30 to 8:30 a.m. and for northbound direction 4:30 to 7 p.m. In Sonoma County, the existing hours of operation in both directions are 7 to 9 a.m. and 3 to 6 p.m.

During the HOV signage construction, the existing hours will remain in effect. Motorists may see new signage with updated hours, but these hours will not be in effect until the completion of the Marin Sonoma Narrows B-7 project projected to finish by the end of August/early September 2025. Caltrans is activating changeable messages signs along the entire corridor to provide advance motorists' information accordingly.

Motorists may experience some additional delays and increased travel times during the construction and transition period as the traveling public gets adjusted to the new hours in both counties.

HOV lanes reduce traffic by increasing vehicle occupancy as people switch to ridesharing or using transit. Carpool lanes carry more people than general purpose lanes and improve the efficiency of the freeway system. HOV operating hours are typically set to cover the periods of peak congestion and short time blocks leading up to and after those peak periods.

The HOV hours for US-101 were determined through an analysis of traffic data that was collected in the summer of 2024.

Construction for the Marin Sonoma Narrows B-7 project 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.

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 the Richardson Bay Bridge near Sausalito in Marin County to Windsor in Sonoma County. HOV lanes are scheduled to be open to use in the summer of 2025.

For more information about new uniform HOV lane hours, see bit.ly/3HoVfOO

Please drive with caution. Slow for the Cone Zone and Be Work Zone Alert.

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