Thursday, June 20, 2024

This Spring, the Federal Highway Administration published a summary of a study looking at data from Cambridge and four other cities. The conclusion: Separated bicycle lanes resulted in approximately 50 percent reduction in bicycle crashes compared with traditional paint-only bike lanes. Already in 2015, the Massachusetts Department of Transportations’ Separated Bike Lane Planning & Design Guide summarized the then-available body of research evidence on these lanes (Chapter 1, Page 4), noting that:

  • “Separated bike lanes attract more people to bicycling.”
  • “Women express a preference for separated bike lanes.”
  • “Separated bike lanes improve safety for all road users.”

Based on this and other research, and significant community engagement, the City’s 2015 Bicycle Plan called for a complete network of separated bicycle lanes; significant installation started in 2017. In 2019 and 2020, the City Council accelerated the installation of the lanes with the passage of the Cycling Safety Ordinance.

And yet, while city, state and federal experts consider separated bicycle lanes to be a proven safety technique, some opponents claim they are dangerous and increase traffic injuries. In a recent opinion piece published by a group trying to sue Cambridge to remove bike lanes, they suggest the safest infrastructure is no infrastructure: Cyclists should ride in the street with motor vehicles and behave the same way as motor vehicles. Contrary to the city’s focus on infrastructure that protects against mistakes and works for a wide range of abilities, they suggest “cyclists … and pedestrians must learn to assume responsibility for their own safety.”

We  evaluated these competing theories of street design by comparing outcomes in Cambridge to outcomes in locations following the no-safety-infrastructure approach. Cambridge is certainly an outlier – we would say a leader – in the extent of its separated bike lane installation and other safety infrastructure. The rest of Massachusetts is much closer to bike lane opponents’ preferred street designs, for the most part either lacking separated bicycle lanes or at best lagging far behind.

To compare the two approaches, we chose two metrics (for more details on why, and the raw numbers, see the full report):

  • For Cambridge: Crashes in Cambridge that resulted in EMS transport to the hospital, a good proxy for the severe injuries that the city’s Vision Zero policy seeks to eliminate, and used by the Cambridge Police Department in its annual report. This includes crashes for all modes of transit (motorists, pedestrians and cyclists), as long as someone was taken to a hospital.
  • For Massachusetts (excluding Cambridge): Traffic fatalities in the rest of the state for all modes of transit; and for pedestrians and cyclists only.

Cambridge began major installation of its lanes in 2017, so we compared each metric’s change over time from the 2016 baseline level. By 2022, Cambridge had installed 11 additional miles of separated bike lanes on high-volume or high-crash streets, plus numerous other investments in street design safety improvements.

Here’s what the resulting outcomes look like:

The figure above shows a stark reduction from 2016 levels in crashes resulting in emergency medical transports in Cambridge (the blue line in the top graph) as the lanes were installed in Cambridge. Conversely, in the rest of Massachusetts, traffic fatalities and fatalities involving pedestrians or cyclists have increased compared with pre-pandemic levels (red and orange lines). Note that 2020 is anomalously low, presumably due to the pandemic.

The Cambridge Police annual report from 2021 reaches a similar conclusion, looking at a different data measure: “In 2021, there were 1,172 crashes reported … down 21 percent when compared to the 10-year average of 1,479 crash reports.” The Cambridge post-crash hospital transport data for 2022 is still preliminary and will likely be revised slightly upward, but the message is similar: Cambridge is much safer compared with 2016, even as Massachusetts traffic fatalities rise.

The city’s transportation department is a leader in traffic safety, relying on proven safety techniques endorsed by state and federal experts; this includes separated bicycle lanes, but also reduced speeds, leading pedestrian intervals and much more. To achieve the goal of zero fatalities and severe injuries from traffic crashes, we must continue implementing safer infrastructure based on the city’s proven expertise.