The intervention works, and it has held.

Both College Avenue (Menlo Park) and Sanchez Street (San Francisco) are designated bicycle corridors. Sanchez had a minimal, low-cost intervention five years ago.

Sanchez Street average daily vehicle traffic, before and after
1,750Pre-impl → 3202021 → 3202023 → …Our 2026 fetch
Pre-implementation Sanchez Street carried 1,750 vehicles per day. SFMTA's 2023 Slow Streets Evaluation Report measured 320 in 2021 and 320 again in 2023. Our 2026 sensor measurement shows the reduction has held for five-plus years of sustained, measurable change on the same street. The interventions were minimal: paint, signage, traffic diverters, gateways. Cost: hundreds of dollars per device, not millions.
The diversion question

"Where did those 1,430 vehicles go? Won't they just dump on other neighborhood streets?"

No, and this is the point of the network design, not an unintended consequence. Through-traffic belongs on arterials: streets engineered with capacity, signal timing, and continuous lanes for moving cars at the posted speed. Neighborhood streets are for the people who live on them: walking, biking, kids playing, slow local trips.

When SFMTA gave Sanchez minimal calming, navigation apps (Google Maps, Waze, Apple Maps) re-learned within weeks that Sanchez no longer offered a faster route, and routed through-traffic back to arterials where that traffic belongs. The 1,430 vehicles per day that left Sanchez did not concentrate on neighbouring residential streets at any meaningful scale; SFMTA's evaluation tracked the network and confirmed this directly. The diversion happened correctly: back to the arterial network.

For College Avenue, this means the equivalent intervention does not threaten other neighborhood streets. It sends through-traffic to Middle Avenue, the arterial built to carry it. That is precisely the role Middle Avenue plays in Menlo Park's circulation system. Cars staying on Middle Avenue is the intended behavior; cut-through routing through Allied Arts is the failure mode the intervention is designed to fix. See the College Ave pilot ask → · Read the citywide amendments →

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Sources. Sanchez Street pre-implementation, 2021, and 2023 ADT figures from SFMTA's 2023 Slow Streets Evaluation Report. NACTO bike-boulevard target criteria from the NACTO Urban Bikeway Design Guide. All other figures computed live from sensor measurements on each street, over the same Mar 31 – Apr 24, 2026 representative weekday sample (excluding weekends, spring break, and the install/calibration window). Methodology: speed metrics use the per-hour passenger-car speed histogram the sensor reports (heavy-vehicle speeds aren't classified separately); volume counts include cars + heavy vehicles.