Frequently Asked Questions

Project Design

What is an express lane?

How Expresss Lanes Work

How do express lanes work?

The San Mateo 101 Express Lanes will prioritize 3+ carpools and buses by always allowing them access to the lanes at no charge. When an express lane is not full with carpools or buses, the excess capacity can be sold to other drivers willing to pay for the time advantage. The first priority in managing the lanes is to keep the traffic moving for carpools and buses. Excess capacity is only sold when it won’t harm the travel of those priority vehicles. When capacity is available, dynamic pricing is used to control the demand of paying vehicles. The more capacity that is available, the lower the price. As the express lane reaches capacity, non-priority vehicles are prohibited from traveling in the express lanes. How will the project reduce congestion?

The primary goal of the project is to move as many people as possible within the corridor. With the anticipated population growth, there is a need to implement new, innovative solutions to traffic problems. Adding express lanes provides 3+ carpools and buses with travel time savings when compared with the general purpose lanes. Selling excess capacity, when available, draws non-priority vehicles out of the general purpose lanes. This helps to reduce congestion in these lanes as well. This will move more people through the corridor without reducing the number of general purpose lanes. A more efficient freeway also encourages traffic to use the freeway instead of city streets. Express lanes also promote ridesharing, which can ultimately reduce congestion on the whole freeway.


How long will construction last? Construction to convert the existing HOV lanes from the San Mateo County/Santa Clara County border to Whipple Avenue will begin in March 2019. Construction to add a lane from Whipple Avenue to I-380 will begin later in 2019. Construction is projected to end in 2022. During construction, every effort will be made to minimize impacts on existing traffic flow and neighboring communities.

How will construction impact me?

Construction will require nighttime lane closures on U.S. Highway 101 throughout the corridor. Working at night will minimize impacts on traffic during the day. Construction will include infrequent daytime partial-ramp closures and temporary detours to city streets. The project also includes removing and rebuilding some sound walls adjacent to northbound U.S. Highway 101 in the City of San Mateo.

How will I find out about construction activities?

All lane closures, ramp closures, and construction activities that could disrupt traffic flow will be posted to social media (i.e. Twitter: @CaltransD4) and updated on the Construction Updates page. Construction activity with the potential to affect city streets will be communicated to City and County Public Information Officers, as well.

Where can I get more information?

You can sign up to join our mailing list or ask a question here. You can follow us on @CaltransD4twitter and read construction updates here.