2023 Slow Streets Evaluation Report

When the SFMTA Board approved a permanent Slow Streets Program in December 2022, they required that every Slow Street meet certain data-driven targets to keep everyone safe and comfortable: average vehicle speeds of less than 15 miles per hour (mph), and average daily vehicle volumes lower than 1,000.

The SFMTA Slow Streets team has been hard at work collecting data on streets in the program to understand how they’re performing against these targets. We’re excited to share the results of this evaluation effort, and detail how these findings will inform design changes on Slow Streets.

To gather this data, the team placed pneumatic tubes every four blocks along existing Slow Streets corridors in January of this year to capture vehicle volume and speed data. Of the 18 streets currently included in the Slow Streets Program, the team conducted data collection on 16 of them (Cayuga Avenue and 22nd Street were not included in the analysis because they are not yet implemented).

The good news is that all but four of the existing Slow Streets corridors— (20th Street, Minnesota Street, Noe Street, and Page Street)—are meeting or exceeding the goal of fewer than 1,000 vehicles per day. That means most of our Slow Streets are working to keep cut-through vehicle traffic off of them.

Streets also became measurably safer following implementation of the Slow Street designation: on average, Slow Streets have seen a 48% decrease in collisions following designation, compared with a 14% decrease in collisions citywide over the same time period.

However, while median speeds have decreased following Slow Streets designation and all streets have median speeds of 20 MPH or slower, most Slow Streets have not met the 15 MPH target set by the Board. This means that Slow Streets have slower-moving traffic, but not slow enough to feel safe for our most vulnerable road users.

This Evaluation Report captures how Slow Streets are working in 2023, which lets us see trends to compare to how these same streets were working before they were Slow Streets, and mid-pandemic in 2021. As a whole, Slow Streets are safer than they were before being designated Slow Streets—there are fewer vehicles on them, and those vehicles are traveling slower. A typical vehicle on one of today’s Slow Streets was traveling at 20 MPH before the pandemic, and in 2021 and 2023 that number is now 16 MPH. Back in 2021 in the middle of the COVID pandemic, the typical vehicle on a Slow Street was traveling around 16 MPH, and in 2023 the typical vehicle was also traveling at 16 MPH. The same trend can be seen with the number of cars on Slow Streets—nearly 2,000 vehicles per day prior to the pandemic, 700 in 2021, and 800 today.

The Program team will use the results of this evaluation to inform design changes on streets that aren’t meeting the established speed and volume targets:

• • Slow Streets that aren’t meeting Board-adopted volume targets (4 of 16) will require volume management tools, like traffic diverters and turn restrictions, to reduce the number of vehicles on the street to below 1,000 vehicles per day.
  • Slow Streets that aren’t meeting speed targets (12 of 16) will need traffic calming treatments.

The Slow Streets team will begin the design phase for these design changes now, with designs coming out by this summer.

You can find more details on the methodology in the complete report, along with individual corridor findings. You can peruse all the tools considered on Slow Streets in the 2023 Slow Streets Design Toolkit (SFMTA.com/SlowStreetsToolkit). To learn more about next steps following this evaluation, you can subscribe to updates from the Slow Streets Program and individual corridors on the program website. We look forward to sharing more about how this data will inform next steps for Slow Streets designs across San Francisco!