101/Willow Road Interchange

Map of East Palo Alta containing project location, near US101 and Willow Road.

U.S. Route 101/Willow Road Interchange in Menlo Park to Close for Weekend Starting Friday, October 5, 2018

Willow Road closed 10:00 PM, Friday, October 5, 2018 – 4:00 AM. Monday, October 8, 2018

Connector Ramps Closed until 6:00 AM, Monday, October 8, 2018

SAN MATEO COUNTY - Caltrans will close the Willow Road interchange on U.S. Route 101 (U.S.-101) in Menlo Park for 54 hours, beginning 10:00 pm, Friday, October 5, 2018, until 4:00 AM, Monday, October 8, 2018, to allow workers to shift lanes on the Willow Road overpass onto newly-built bridges. 

U.S.-101 will be open to through-traffic during the weekend closure, but all on- and off-ramps connecting Willow Road with U.S.-101 will be closed from 10:00 PM, Friday, October 5 until 6:00 AM, Monday, October 8.

By shifting traffic onto the newly built bridges, Caltrans can continue with the demolition of the existing overpass, clearing the way to build a larger overpass to handle more traffic.

The new alignment will not be difficult for motorists to follow. During the closure Caltrans will pave two sections of road that will connect Willow Road to the new bridges. As motorists travel eastbound or westbound they will veer slightly to the right to access the new bridges.

Caltrans is upgrading the Willow Road interchange under a $58 million contract that began in September 2017. The project is on schedule for completion in mid-2019.


Through-traffic on U.S.-101 will not be detoured; only traffic that normally would take the Willow Road Exit will be detoured.

U.S.-101 to Willow

  • Northbound traffic exit at University Avenue or Marsh Road
  • Southbound traffic exit at Marsh Road or University Avenue

Willow Road to U.S.-101

  • Westbound Willow to northbound U.S.-101: Take Bayfront Expressway (SR 84) to Marsh Road, left on Marsh Road to northbound U.S-101
  • Westbound Willow to southbound U.S.-101: Take University Avenue to southbound U.S.-101
  • Eastbound Willow to southbound U.S.-101: Turn right on Middlefield Rd, left on University Avenue to southbound U.S.-101
  • Eastbound Willow to northbound U.S.-101: Turn left on Middlefield Rd., right on Marsh Road to NB 101
  • Pedestrian Access: The overpass will be remain closed to pedestrians. The pedestrian shuttle will remain in use throughout the weekend.

Jeff Weiss
Caltrans Public Information
(510) 286-5543

Existing 101 / Willow Road Interchange

The original interchange, a cloverleaf, was built in 1955 and served traffic well for decades. But cloverleaf interchanges, once the paragon of efficiency for moving traffic and conserving land, cannot handle modern traffic volumes, at least not at most locations in the Bay Area.

Why is that? Traffic on cloverleaves bunches up on the overpasses and the freeway underpasses, the places where the “leaves” connect to the “stems.” Look at the diagram on the right. The weaving areas, the light gray area on the overpass (left) and the freeway below it, are very short, forcing driving to accelerate or decelerate, step on the gas to zip ahead of traffic or hit the brakes to allow traffic to weave in. Weaving in such a short section on roadway requires a lot of vigilance. On busy days, it can be particularly difficult. Also, the size of the interchange is relatively small and compact, which may have been a good thing in decades past as it preserved land for other uses. Nowadays with so much additional traffic traveling through the interchange the small size creates congestion.

101 / Willow Road Future Interchange

The exiting Willow Road Interchange is full cloverleaf interchange. To solve the weaving problem, the Willow Road interchange will be updated to a half cloverleaf, (see below) where only half as many of the ramps connect to the overpass or underpass, reducing congestion and easing the strain on motorists by providing much more room to merge.

The Willow Road Overpass project provides an opportunity to build features for bike riders and pedestrians. The new overpass will have sidewalks and two bicycle lanes in each directions. One bicycle lane, meant for casual cyclists, will be separated from traffic with a barrier, while another lane, meant for faster cyclists, will have a designated lane in the traffic lanes.

Caltrans has partnered with other agencies on this project: The San Mateo County Transportation Authority, the City of Menlo Park, the City of East Palo Alto, and the City/County Association of Governments of San Mateo County.

If you have questions about this project, please contact Jeff Weiss at jeffrey.weiss@dot.ca.gov.