SM 101 Express Lanes Project
Stay Informed and Plan for Delays
Caltrans is constructing express lanes on U.S. 101 from the San Mateo County/Santa Clara County Line to I-380 in South San Francisco. Construction is expected to be completed in mid-2022 with the full lanes opening to traffic late-2022.
To sign up for weekly or quarterly updates, email with the subject line 'Weekly' or 'Quarterly' to firstname.lastname@example.org. Follow @CaltransD4 on Twitter for Project updates. Para mayor información en español, visite de abajo. 更多详情的中文,请访问下面.
Existing carpool lanes will be converted to express lanes between the San Mateo/Santa Clara County line and Whipple Avenue (blue solid line) and new express lanes will be constructed between Whipple Avenue and I-380 (red stripped line). This will result in 22 miles of express lanes in each direction of U.S. 101.Scroll down to read Project information, construction updates, Project contact information and link to documents. Also, click on the Frequently Asked Questions link above to read frequently asked questions and check out this week’s construction update by clicking the Construction Update link above.
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- Additional information can be found in the Project Fact Sheet
- Para mayor información visite Hoja Informativa del Proyecto
- 更多详情的中,访问 项目优情况说明书
The San Mateo 101 Express Lanes Project is a multi-year, multi-agency project initiated to reduce traffic congestion and encourage carpooling and transit use on U.S. 101 in San Mateo County.
The Project will create 22 miles of express lanes in both directions on U.S.101 from the San Mateo County/Santa Clara County Line to I-380 in South San Francisco. The San Mateo 101 Express Lanes will seamlessly connect to the express lanes being constructed in Santa Clara County.
A goal of the express lanes is to enable travel speeds of 45 mph or greater, resulting in reduced and more reliable travel times.
Key Project Benefits
- Reduce congestion in the corridor
- Increase person throughput (the number of people moved)
- Encourage carpooling and transit use
- Improve travel time and reliability for express lane users
- Use modern technology to manage traffic
- Make upgrades to pavement and lane striping
Construction of the San Mateo 101 Express Lanes is occurring in two phases:
Phase One – San Mateo County/Santa Clara County Line to Whipple Ave: Phase One construction began in March 2019. During this phase, the Project is converting existing carpool lanes to express lanes from the San Mateo County/Santa Clara County Line to Whipple Ave in Redwood City. Minor construction activities will continue throughout 2020 and 2021.
Phase Two – Whipple Ave to I-380: Phase Two construction began in February 2020. During Phase Two, the Project is constructing new express lanes from Whipple Ave to I-380 in South San Francisco. Project construction is currently scheduled to last through mid-2022. Throughout 2020, construction activities will occur on the freeway lanes, shoulders, ramps, and on local city streets. Beginning early 2021 through mid-2022, construction activities will occur in the freeway median. Lastly, the Project area will be repaved and restriped before the new lane is open for operations.
Construction activities will require nightly freeway lane closures, temporary ramp closures, lane closures on city streets, and the relocation of some sound walls. See below for detailed information on anticipated Lane Closures, and Sound Wall Removal/Reconstruction.
Due to current low traffic volumes, Caltrans has begun implementing nightly lane closures beginning at 7:00PM, and ending by 6:30AM, Sunday night to Friday morning. Caltrans will continue to provide real-time traffic conditions via changeable electronic message signs placed within the construction zone. Caltrans will monitor traffic delays and make adjustments as necessary, though project related delays are anticipated to be minimal during this time.
Travelers will be able to see real-time traffic conditions from changeable message signs placed in the construction zone. The Smart Traffic System is being implemented during construction to provide up to date information, improve safety, and reduce congestion.
Sign up for weekly updates to get details on the construction activities planned each week.
Sound Wall Removal/Relocation in San Mateo
As part of project construction, Caltrans has removed and is relocating sections of sound wall in the City of San Mateo throughout 2020 and early 2021.
Additional information can be found here.
For questions during construction, or to request a presentation from a project representative, contact the Caltrans Public Information Officer:
Alejandro Lopez at (510) 385-6856 or email firstname.lastname@example.org.
To sign up for weekly or quarterly updates, email with the subject line 'Weekly' or 'Quarterly' to email@example.com.
You can download other project documents at San Mateo County Transportation Authority’s documents page.