Highway 101 Auxiliary Lane Project

Auxiliary lanes provide a merging area for cars to enter and exit the freeway. The benefits are two-fold: local drivers can use the freeway for short trips to neighboring communities without having to merge into fast-moving traffic and freeway traffic isn’t as impacted by slower drivers entering and exiting the freeway.

The Highway 101 auxiliary lane project was identified as a congestion relief project in the original Measure A initiative. Plans called for the lanes to extend from county line to county line, a total length of 26 miles.

The project has been completed in phases. In 1997, auxiliary lanes were built from Third Avenue to the State Highway 92 Interchange (1.5 miles). In 2001, the section from Hillsdale Boulevard in San Mateo to Ralston Avenue in Belmont (1.5 miles) was completed. In 2004, the lanes were extended from Ralston Avenue to Marsh Road in Menlo Park (3.5 miles). Construction on a 4.5 mile section from Millbrae Avenue to Third Avenue in San Mateo was completed in 2010.

Work on the segment between Marsh Road in Menlo Park and University Avenue in Palo Alto is nearly complete. Construction on the next segment, between University Avenue and Embarcadero Road, will begin shortly. This is the last segment of the southern end of the project. For more information about the project, click here.