Crossing Highway 101: Hillsdale Boulevard

The eight lane Highway 101 partitions the San Francisco Peninsula with an eight lane wall of traffic from San Jose to San Francisco. The Caltrain line with its 50,000 daily commuters runs to the west of 101. Businesses, jobs and residential areas can be on either side of the highway. Many of the three percent of Bay Area commuters who ride bikes must find a way to cross this highway.

Consider Hillsdale Boulevard in San Mateo, California, which is fairly typical of many 101 crossings. In this from Google Maps aerial view, Hillsdale crosses from the lower left to the upper right of this image.

Hillsdale Boulevard @ Highway 101, San Mateo, California

Hillsdale approaching and crossing 101 in either direction has three lanes of fairly fast moving traffic. The right lane for both sides is an auxiliary lane; that is, an exit-only lane that becomes an on-ramp for the freeway.

People on bikes cross by (1) riding their bikes across on the sidewalk, waiting for gaps as they cross the freeway ramps; (2) riding to the far right of all traffic, then stopping where the ramps begin to turn to wait for a gap; or (3) taking the middle of three high speed lanes.

The nearest alternative crossing in either direction is at least two miles away, which means a four mile detour is required to avoid Hillsdale altogether. Many people exactly that.

Hillsdale Boulevard Bicycle / Pedestrian Bridge

Because of persistent demand for a better bike crossing at this location, San Mateo County first investigated a bike / pedestrian bridge near Hillsdale Blvd in 2007. The death of a 68 year old man on this bridge in 2009 underscored the importance of safer cycling facilities here.

This proposed overcrossing is now in the preliminary design phase. The city of San Mateo plans a bridge to provide a separate path for the exclusive use of bicyclists and pedestrians and minimize conflict with vehicles. This bridge will also complete the bicycle network connection from the Hillsdale Caltrain Station to the neighborhoods east of US-101 and Foster City.

If you would like to learn more about this project, the city invites you to their Hillsdale Blvd bike bridge community workshop on Wednesday, February 5, 2014, 7:00 PM — 9:00 PM at the San Mateo Police Department, 200 Franklin Pkwy, San Mateo, CA 94403.

To learn more about this project, visit this page. If you’d like to keep up to date on other bicycling issues for San Mateo County, I encourage you to sign up for the BikeSMC group.


  1. Thanks for reporting on the Hillsdale Bridge workshop. If you are interested, I can send you a short video of what it’s like to bike across the overpass (circa 2007). It’ll make your hair stand straight up. You’ll see how you have to wait for an opportune moment to cross and even then you have to share the lane because motorists just want to go 35-40 mph no matter what.

  2. For intersections of similar ilk I try to be near the last vehicle through the last green light before crossing a freeway. This gives me a low traffic run and hopefully the next light at the top turns green before the down hill section and I have some speed before I have to deal with the people coming off the freeway and turning right, in this case onto Hillsdale.

    The real solution is to ban this type of intersection and get rid off all the turns that have no traffic control. These are bad for any user other than a speeding automobile. they disregard safety for all other users.

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