Drivers who exit northbound US 101 at Hillsdale Boulevard will need to find another way overnight starting Monday.
Caltrans announced it will close the northbound US 101 off-ramp to East Hillsdale Boulevard beginning Monday, July 20, with nightly closures running from 10 p.m. to 7 a.m. Crews will use the overnight windows to install new traffic signals and lighting on the ramp, according to a Caltrans District 4 press release issued July 16.
The highway carries between 240,000 and 270,000 vehicles per day within San Mateo city limits, according to Caltrans traffic data.
The detour
Northbound drivers headed for East Hillsdale Boulevard should take the connector off-ramp to eastbound State Route 92, exit at Edgewater Boulevard/Mariners Island Boulevard, then turn onto East Hillsdale Boulevard. Caltrans said drivers should follow posted detour signs and allow extra travel time.
Part of a bigger project
The ramp work falls under the $45 million US 101–SR 92 Short-Term Improvements Project, co-sponsored by the San Mateo County Transportation Authority and the City/County Association of Governments of San Mateo County. Construction began in spring 2025 and is expected to wrap up in summer 2028.
At the Hillsdale interchange specifically, the project will widen the northbound off-ramp to add queuing space for exiting vehicles, upgrade the northbound on-ramp to current standards, add pedestrian crossing enhancements, and extend the third eastbound lane on the Hillsdale overcrossing.
The broader project also addresses the westbound SR 92 to southbound US 101 loop connector, merge lanes between US 101 and eastbound SR 92, and the southbound US 101 Fashion Island Boulevard off-ramp.
What residents should know
Caltrans has not announced an end date for the nightly closures. The agency said nearby residents should expect overnight noise and vibrations and noted it will use sound barriers and other mitigation strategies to limit disruption.
All work is weather dependent, according to Caltrans.
This is not the first overnight closure tied to the project. Caltrans has conducted similar ramp shutdowns on multiple occasions since February 2026, including closures in March, April, and June.
For real-time traffic conditions during the closures, Caltrans directs drivers to its QuickMap tool at quickmap.dot.ca.gov. Residents with questions can contact Caltrans public information officer Jeneane Crawford at [email protected] or (510) 390-3253.
Key dates
- Monday, July 20: Nightly Hillsdale off-ramp closures begin (10 p.m.–7 a.m.)
- Summer 2028: Expected completion of the full US 101/SR 92 interchange improvement project
