The experts were right: Cambridge roads are getting safer

In the spring of 2023, the Federal Highway Administration published a brief looking at data from Cambridge and 4 other cities. The conclusion: separated bicycle lanes resulted in approximately 50% reduction in bicycle crashes compared to traditional paint-only bike lanes. Yet a recent opinion piece, published under the title “Analysis of Cycling Safety in Cambridge Under the Cycling Safety Ordinance”, purports to show that Cambridge’s growing network of separated bike lanes is increasing injuries. This false claim deserves a rebuttal.

Cambridge Bicycle Safety is a grassroots volunteer group that advocates for safer infrastructure for people on bicycles. We have spent many years advocating for protected infrastructure in order to reduce injuries and deaths, and while there is much more to be done, we are happy to see the progress Cambridge has made.

In contrast, the group responsible for the ‘analysis’, Cambridge Streets For All (CS4A) aims to stop and remove separated bike lanes in the city. The leadership of this group initially tried to delay and cancel the rollout of bike lane projects through policy orders in City Council meetings. When unsuccessful, they escalated  to lawsuits: CS4A asked a judge to remove all quickbuild separated bike lanes in the City [6/10/2022 preliminary injunction memorandum, page 2, for Cambridge Streets for All et al vs. City of Cambridge]. Having failed to convince multiple judges of their legal arguments, CS4A has now switched to statistical fear-mongering.

“Mercenaries attacking villages” or proven traffic-engineering safety measure?

The main author of the ‘analysis’, John Hanratty, stated in an affidavit to the CS4A lawsuit that the Cycling Safety Ordinance is a “deceptive” move by the City Council, “pander[ing] to a small, well-organized special interest group” which later in the affidavit he compares to “seasoned mercenaries attacking unsuspecting villages.”

Reality is more prosaic than Hanratty’s hyperbole: this legislation was preceded by many years of professional planning by City staff, which in turn was based on extensive safety research. Already in 2015, the MassDOT Separated Bike Lane Planning & Design Guide summarized the 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 SBLs, and significant installation started in 2017. When the Council codified and accelerated the City’s pre-existing safety practices in the Cycling Safety Ordinance in 2019 and 2020, City staff provided significant input to the language and designs of both versions. 

The City’s approach to traffic safety was given recent support by the previously mentioned Federal Highway Administration study. After looking at data from Cambridge and four other cities, the FHWA’s concluded that “with the implementation of SBLs, a transportation agency can expect to see a reduction in bicycle crashes.”

Implementing safe infrastructure: Cambridge vs. the rest of Massachusetts

While City, state, and Federal experts consider separated bicycle lanes to be a proven safety technique, CS4A and Hanratty claim that separated bicycle lanes are dangerous and increase traffic injuries. Instead, they offer an alternative, an obsolete theory that suggests the safest infrastructure is no infrastructure: cyclists should ride in the street with motor vehicles and behave the same way as motor vehicles (see appendix 1 for more). Contrary to the City’s focus on infrastructure that protects against mistakes and works for a wide range of abilities, CS4A and Hanratty suggest “cyclists … and pedestrians must learn to assume responsibility for their own safety.”

We can evaluate these two competing theories of street design by comparing outcomes in Cambridge to outcomes in locations following CS4A’s no-safety-infrastructure approach. Cambridge is certainly an outlier—we would say a leader—in the extent of its separated bike lane (SBL) installation and other safety infrastructure. In contrast, the rest of Massachusetts is much closer to CS4A’s preferred street designs, for the most part either lacking separated bicycle lanes, or at best lagging far behind.

To compare the two approaches, Cambridge Bicycle Safety chose two metrics:

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

(For more details on why these metrics were chosen, and the raw numbers, see the appendix.)

Cambridge began major installation of SBLs 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:

Two graphs: first shows Cambridge EMS transports after crashes declining since 2016, while traffic fatalities in MA are much flatter and then rise significantly in 2021 and 2022.

The second graph shows increasing miles of separated bike lanes, from almost none in 2016 to more than 11 miles at end of 2022.

The figure above shows a stark reduction from 2016 levels in crashes resulting in emergency medical transports in Cambridge (blue line in top graph), as SBLs were installed in Cambridge. Conversely, in the rest of Massachusetts, traffic fatalities and fatalities involving pedestrians or cyclists have both increased compared to 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% when compared to the ten-year average of 1,479 crash reports.” The Cambridge post-crash EMS transport data for 2022 is still preliminary, and will likely be revised slightly upwards, but the message is similar: Cambridge is much safer compared to 2016.

CS4A suggests that City actions are increasing Cambridge traffic injuries. In fact, Cambridge is getting safer, while at the same time, Massachusetts traffic fatalities are on the rise. The dangerous status quo elsewhere in the state is the alternative promoted by the CS4A.

The City’s transportation department is a leader in traffic safety, relying on proven safety techniques endorsed both 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.

Appendix 1: A partial list of flaws in Hanratty and CS4A’s ‘analysis’

The CS4A ‘analysis’ suffers from a number of flaws. A partial list:

  1. Looking at only a small minority of the many SBL projects installed by the City.
  2. Only comparing two years, 2019 and 2022, ignoring the much longer history of separated bicycle lanes in Cambridge that predates the Cycling Safety Ordinance.
  3. Ignoring broader trends, like the significant state-wide increase in fatalities between 2019 and 2022; Cambridge is not an island, with many drivers coming from outside the City.
  4. Relying on a subset of the data. As described below, the Cambridge crash log is often missing entries, which is why the Cambridge Police manually reanalyze all written records before publishing their annual report.

The ‘analysis’ also promotes an obsolete theory known as “vehicular cycling”. Hanratty quotes John Forester, the main promoter of the idea, who suggested that to keep safe, “cyclists [should] act and [be] treated as drivers of vehicles.” As an example of the practical flaws in this scheme, consider that:

  • 25 MPH is the speed of motor vehicle traffic on Mass Ave (or sometimes higher when drivers speed).
  • 10 MPH is Google Maps’ fairly accurate assumed speed for normal city biking, by fit adults.
  • Children, seniors, people with disabilities, and those less experienced with biking may be even slower.

This difference in speed, combined with large and heavy motor vehicles with large blindspots, is a recipe for disaster when people on bikes try to share the road. Vehicular cycling has for the most part been abandoned; see for example this historical survey from 2018.

Appendix 2: The data, and how we chose our metrics

The data used to generate the graphs above includes:

  1. Total quickbuild separated bike lane miles in Cambridge, based on [1] and [2].
  2. Cambridge traffic crashes that required ambulance/EMS transport (for all crashes, motor vehicle, pedestrian and/or cyclist) as a proxy measure of serious injuries, based on the Cambridge Police Department annual report for 2021, with the crash log used for preliminary 2022 data.
  3. State-wide traffic fatalities (with Cambridge fatalities excluded) as a baseline, taken from a statewide database.
YearMiles of quickbuild separated bike lanesCambridge crashes requiring EMS transportsMA traffic fatalities (all)MA traffic fatalities (peds + cyclists only)
20207.61119(lowered by pandemic)34162(lowered by pandemic)
20219.4(at end of year)23341381
202211.5+(at end of year, estimate)203(preliminary data)437108

Choice of metrics

Our comparison aims to show the big picture: whether or not the City is doing a good job on traffic safety overall. The City’s main focus is on reducing severe injuries and fatalities, so that is what we want to measure. A comparison to the rest of Massachusetts is useful as it both illuminates broader trends, like the post-pandemic fatality spike, and allows us to see the impact of Cambridge’s particular choice of policies and street interventions.

While the state traffic crash database also includes some measure of injuries, as does the more detailed Cambridge crash database, the injury measure is problematic:

  1. Thousands of crashes every year don’t have injury levels recorded at all.
  2. Some of the severity level names are ambiguous.
  3. Deciding on an injury level can be a subjective decision.
  4. Electronic data entry is apparently not as reliable as the original written reports; see below.

In contrast to injury levels, fatalities are unambiguous, and are severe enough that one assumes they tend to be reported more consistently. And they should correlate well with major injuries, given a sufficient number of instances. Massachusetts-wide traffic fatalities are therefore used as a proxy measure, with Cambridge fatalities subtracted.

Annual traffic deaths in Cambridge are so low that they don’t provide sufficiently fine-grained information about trends—for example, the one fatality in the 2022 police log happened in a parking lot. So we use crashes with EMS transport to the hospital as reported in the Cambridge Police annual reports, currently available up to 2021. This is a metric also used by the Cambridge Police.

The Cambridge police log in the Open Data portal also lists EMS transports, but according to a discussion with CPD that data is less accurate. Per CPD, annual reports include a manual review of all written reports to catch missing electronic data entries. As 2022 data is not yet available, we used the crash log data as a preliminary source.