Full Overnight Closure December 4-5

San Mateo County ― Caltrans will conduct its annual mandatory emergency response drill at the State Route 1 (SR-1) Tom Lantos (Devil's Slide) Tunnels. The drill will take place overnight starting on Thursday, December 4, 2025. This exercise will include testing of fire suppression and communication systems, exercise scenarios, and multi-agency coordination. For the safety of crews and the public, both the northbound and southbound lanes will be closed during the exercise.

Schedule

Lanes close: Thursday, December 4, at 8 p.m.
Lanes open: Friday, December 5, at 4:30 a.m.

Detours

Heading southbound from Pacifica

From SR-1, exit at Sharp Park Road north towards Skyline Blvd. Turn right at Skyline Blvd. continuing to southbound I-280. Follow I-280 and exit on SR-92 west to Half Moon Bay.

Heading northbound from Half Moon Bay

Take eastbound SR-92 and enter northbound I-280. Exit at Skyline Blvd. and follow the road to Sharp Park Road. Turn left on Sharp Park Road and follow it to SR-1.

This emergency management exercise will be a coordinated effort with the participation of Caltrans, the California Highway Patrol (CHP), State Fire Marshals, the San Mateo County Sheriff's Office, Pacifica Fire and Police Departments, North County Fire, Cal Fire, and other first responders.

Please follow detour signs.

All work is weather dependent. Please drive with caution. Thank you for your patience as we work to maintain our state's highways, bridges, and tunnels.

For real-time traffic, click on Caltrans QuickMap: https://http://quickmap.dot.ca.gov/