Northbound drivers on Highway 101 are advised of two night closures in Petaluma that will remain in force through Thursday, Aug. 29.

As part of the Marin-Sonoma Narrows widening project, one northbound lane will be closed 11 p.m.-6 a.m. between the Sonoma County border and the Kenilworth pedestrian overcrossing. At least one lane will remain open.

The northbound U.S. 101 on-ramp from State Route 116 will be closed from 10 a.m.-5 p.m. through Thursday, Aug. 29. Caltrans suggests the following detour route: From Petaluma Boulevard South, continue north to East D Street. Turn right, then right again on Lakeville Street, left on Caulfield Lane, left on S. McDowell Boulevard., left on E. Washington Street, and turn left at the northbound U.S. 101 loop on-ramp.

The northbound U.S. 101 off-ramp to Petaluma Boulevard South will be closed from 9 p.m.-6 a.m. Wednesday, Aug. 28.

Unless there are weather delays, Caltrans also will reopen the northbound Highway 101 on-ramp from Petaluma Boulevard South on Thursday morning, Aug. 29, which may cause delays.

For more information about the project, visit, call the message line at 781-2245 or follow Caltrans District 4 on Twitter @Sonoma101.