City staff is examining the reports of crashes on Cambridge streets where separated bike lanes are being planned – Cambridge Street, Main Street and Broadway – to identify safety hazards and devise remediations. I appeal to City Manager Yi-An Huang to examine the crash reports for streets that already have “quick-build” separated bike lanes for the same purpose.
On two streets where separated bike lanes were first installed, the number of crashes has increased.
In August 2017 a Pilot Safety Project was installed on Cambridge Street between Quincy and Antrim streets, and in September 2021, Cycling Safety Ordinance “quick-build” lanes were installed on Massachusetts Avenue between Trowbridge and Inman streets. These two segments, Cambridge Street West and Mid-Massachusetts Avenue, are similar to the three road segments now in planning: They have high traffic volumes, had parking and loading areas on both sides that served nearby residents and businesses and are too narrow to accommodate two protected cycle lanes without removing parking on one side. It is to be expected that the addition of “quick-build” lanes will have similar impacts for safety – positive and negative – on the streets in planning.
Cambridge Police Department reports show that the annual numbers of motor vehicle crashes with vulnerable users on Cambridge Street West and Mid-Massachusetts Avenue are no lower than before the lanes were installed and that there are now more crashes involving pedestrians.
The following table of reported pedestrian and cyclist crashes in the CPD database shows the total numbers of crashes for 2015 and 2016, before any lanes were installed, and for 2022 and 2023, after they were installed on both streets.
There were 27 total crashes in the latest two-year period, compared with 21 crashes in the two years before the first lanes were installed. Most of the increase was for crashes involving pedestrians. Crashes involving cyclists also increased.
It’s time to find out if the quick-build design creates safety hazards as it eliminates others.
Expert review of these crashes by police and engineering staff is needed to identify and remedy safety hazards in the new layout to avoid repeating them in new projects.
I appeal for a “data-driven approach” to safety called for by Cambridge’s Vision Zero policy. Genuine progress toward safer streets and zero serious injury crashes depends on it.,
The writer is the former chair of the Cambridge Board of Traffic and Parking. He is the vice chair and interim chair of Cambridge Streets for All.
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The opinion misses a critical part of safety analysis: that the crash _rate_ is what is most important. A rigorous analysis of crash rates by professional staff is included in the city’s “Bicycling in Cambridge” report: https://www.cambridgema.gov/-/media/Files/CDD/Transportation/Bike/bikereports/20231023bicyclingincambridgedatareport_final.pdf
There are three important considerations to analyzing crashes and crash rates:
Increased Cycling: From 2015 to 2023, the number of cyclists has surged, and while crashes may have risen, the crash rate per cyclist actually dropped [See Report].
Higher Reporting: Improved reporting mechanisms and policies have led to more recorded incidents, not necessarily more crashes.
Reduced Severity: Crash severity has decreased, [See Report] showcasing the effectiveness of new policies and designs.
Additionally, it is important context to note that John Pitkin has been the Interim Chair of Cambridge Streets for All, the group which unsuccessfully sued to stop and remove quick-build bike lanes in Cambridge.
Thanks Chris, “crash rate” is the first thing I thought of when I read this essay. Unfortunately, the numbers don’t all come from the same place so it’s easy to be misled by rising number of crashes.
I would love to see absolute crash numbers come down too, but I think that will require concrete not just flex posts, and a bike network with no gaps.
Yes, it’s the rate that matters.
The funny thing is that my kid in elementary school *just* took a class in which explained this kind of deceptive misrepresentation of data!
A bit more on injury severity—
One of the biggest impacts on how serious a crash injury is for pedestrians (and people on bikes) is the speed of the motor vehicle hitting them. And what Pitkin won’t tell you is that the the west Cambridge St bike lanes significantly reduced speeding.
First, why speed matters much more than you would think:
According to the Federal Highway Administration (https://highways.dot.gov/safety/proven-safety-countermeasures/appropriate-speed-limits-all-road-users):
– “A driver traveling at 30 miles per hour who hits a pedestrian has a 45 percent chance of killing or seriously injuring them.”
– “At 20 miles per hour, that percentage drops to 5 percent.”
Notice that reducing speed by 33% reduces chances of bad outcomes by around 90%! It’s not a linear relationship, if you look up the underlying formula it’s actually quadratic, so even small differences in speed make a big difference. This is why the City is currently setting speed limits to 20MPH across most streets.
However, merely setting the speed limit doesn’t necessarily change the actual driving behavior. As we’ll see in a second, there was plenty of illegal speeding on Cambridge St before the redesign. To reduce actual speeding you need street design changes.
That’s exactly what happened as part of the installation of the west Cambridge St bike lanes. As shown in the City study (https://www.cambridgema.gov/-/media/Files/CDD/Transportation/Projects/cambridgestreet/SpeedandCountDataCambridgeStreet.pdf):
– Before the bike lanes were installed, 15% of drivers were going faster than 31 MPH, and 5% of drivers were going faster than 35MPH.
– After the bike lanes were installed, those numbers dropped to 25MPH and 28MPH.
In other words, we have data showing that Cambridge St bike lanes significantly reduce speeding, therefore significantly reducing the injury severity of any crashes that do happen. Pretty important given this is a route to CRLS, the library, and the War Memorial complex.
Why are you adding together crashes from two completely different street segments? This obscures the fact that, even by your own haphazard analysis, the total number of crashes still decreased on Cambridge St (9 before and 8 after in the intervals you chose).
And why are you comparing 2015-2016 to 2022-2023, but ignoring all the other years of data? If I arbitrarily compared 2018-2019 to 2022-2023 for Mass Ave, it would show a net *decrease* in crashes (22 before and 19 after, and that’s even avoiding the pandemic year).
And that’s not even addressing the fact that you forgot the *denominator* in all of these calculations, the number of people walking and biking.
Not only is your data oddly cherry-picked and only includes nominal count instead of rate, it also doesn’t account for the changes in driving behavior since the pandemic, where driving deaths and injuries have spiked nation-wide.
All actual, peer-reviewed data on the matter shows that these types of projects improve safety, not just for cyclists, but for all road users.
We all know you’re anti-bike, John, just say it with your chest instead of trying to hide behind bad data.
When I read John Pitkin’s letter, I wondered how many hours it would be before the indispensable Chris Cassa debunked John’s argument by pointing out that John was ignoring crash rate, severity and other details. John had to know that this was coming, as it has been pointed out many times before. Yet John’s letter contained no prebuttal of the obvious response. If John had a good argument,why didn’t he make it? He is showing us that he doesn’t have good arguments.
This is total nonsense. You need to look at crash *rate* data, not just the number of crashes.
Bike lanes increase overall cycling. To determine if bike lanes affect accidents, you need to examine crash *rate* data.
An error like this would earn a failing grade in an introductory class.
Cambridge Streets For All (Cars) repeatedly makes these rookie mistakes. Either they don’t know what they’re doing or they’re spreading disinformation.
CSFA: Find someone who knows how to analyze traffic data. You do not.
This letter is ridiculous. Pitkin and CSFA are not using the correct data. Crash *rate* data is needed to determine if safety has changed.
They should know this. They’ve heard it before. They’re either incompetent or deliberately spreading propaganda, or both.
Federal reports using crash *rate* data show a decrease in accidents.
Pitkin should have realized he was doing something wrong when his results differed from those of the experts, but apparently not.
To summarize:
John Pitkin uses incorrect data. Crash rates, not raw numbers, should be analyzed. He selectively examines only a few short segments of the bike lanes and narrows the focus to limited time periods.
This approach appears to manipulate the data to get desired results.
Pitkin and CSFA: The city is full of people who understand data analysis. You do not.
The impact of bike lanes is already well-documented. Federal scientists have properly analyzed the data and found a 50% reduction in accidents.
Pitkin and CSFA: Stop trying to mislead people. You are spreading disinformation.
Yet another Cambridge streets for cars crash course on how to lie with statistics and via omission. We clearly shouldn’t expect anything else from them but why are their repeated lies still being published?
If I had an agenda, like not wanting more bike lanes installed, and I wanted to use data in a dishonest way to convince people to take my side, this is just the article I would write.
Pretending to care about safety while advocating against safety measures is quite Orwellian, and it’s sad that the author feels that this is the best way to achieve his goals.
I understand that Cambridge Day doesn’t have a staff statistician to review Letters. However, it should be clear to everyone that CSFA is dishonest, manipulating data to push their agenda.
I have donated to Cambridge Day in the past, but I will no longer support it. Cambridge Day is spreading propaganda. They may not have realized it initially, but it is now obvious.
Come on, Cambridge Day! Would you publish any garbage someone submits in a letter?
The problem is not that Jon Pitkin believes this – he’s allowed to be a bad amateur data analyst if that’s how he wishes to spend his free time. The problem is that Joan Pickett believes it, and this type of poor data interpetation influences others who have decision making ability.
It seems pretty clear to me that the real concerns of bike lane opponents are parking convenience, impacts to small business, traffic etc. I think they should just be honest that those are their concerns, instead of pretending to care about bicyclist safety and doing obviously flawed data analysis exercises. As others have noted, real systemic analyses have found enormous safety benefits of protected bike lanes:
https://drive.google.com/file/d/1oUZ2mKGBSWwBwpU3i_2RGm9NlWhOi1mw/view
This is another example of CSFA members willfully ignoring city and other data that disproves their posturing that bike lanes are less safe (than the driver-centric status quo) and are destroying local, small businesses. They should just be honest about their true priority: preserving unmetered and unrestricted street parking. Then the debate can be honest and focused on how much parking it is appropriate to preserve in relation to meeting the city’s commitments to Complete Streets and Vision Zero.
There are 16 comments on this letter, all highlighting the deep flaws in the CSFA data analysis.
Cambridge Day, stop publishing propaganda from this group. They are clearly fabricating lies.
Would you publish a letter making false claims about election fraud? Why are you publishing this nonsense?
I agree with Frank D. The only description of the opinion section says “A separate section is set aside for (also fact-based) expression of opinion, and all voices are welcome in its pages.”
Why are Cambridge streets for cars mistruths continuing to be printed. This and several other submissions by them include major factual inaccuracies that are convenient for their talking points. People should not be allowed to publish lies in the local paper to push their agenda.
Cambridge Day is essentially a labor of love, and there is no professional staff to review stuff to the degree we would all be happy with. So while I was first to debunk this poor analysis, I want to take a moment to remind folks that we benefit so much from having a local news outlet, and thank you Marc Levy for keeping it going. One idea to suggest is that we could have a point-counterpoint the next time something like this gets submitted.
I do especially agree with Jan’s take — let’s just be honest about what this is really about: some people wanting the convenience of plentiful free parking. These redesign projects challenge that status quo in a more equitable way for people taking transit, walking, and biking. There are many of our neighbors who can’t afford a car or who would prefer to travel in a more efficient or socially conscious way.
CS4A, if you’re listening, maybe it’s time we at least stop these usual arguments / tropes:
* We all know that bike lanes make biking safer (duh.)
* We have plenty of local evidence that business districts are doing well. As Paul Toner pointed out this morning, North Mass Ave has no rampant storefront vacancies (the last one I know is gone after the planned business opens within Season to Taste, which moved.) Same with Cambridge St ‘West’ (after Asaro replaces Darwin’s next week!), and Brattle St. Porter Sq just announced three businesses are expanding and two are being re-opened after COVID closures.
* There is no epidemic of cyclists hitting pedestrians. It’s just not there in the data. The most serious and prevalent danger continues to be cars hitting pedestrians and cyclists.
* The Cambridge Police Commissioner and Fire Chief both said that emergency response times have not been an issue in a recent council committee hearing.
* People do not know about these projects or have not had their voices heard… well this one is just getting ridiculous at this point.
I don’t mean to cast aspersions on the editors. Cambridge day is invaluable to understand what’s going on in Camberville.
That said, I do think people with a pattern of misrepresentation and outright lies should be treated with greater skepticism and there are a few fixtures of the opinion pages that applies to. It’s reasonable to assume good intentions but not yet someone demonstrates their willingness to peddle disinformation it is reasonable to abandon that assumption and place their claims under higher scrutiny.
@slaw, I can’t really disagree with that.
On a positive note, the lanes are working!
https://x.com/aswanson_1/status/1793405193373008296
law, FrankD: “…stop publishing propaganda from this group.” My article was not on behalf of or authorized by CSA. The editor added my CSA affiliation with a view to “full disclosure.”
The article expresses exactly one opinion: that the City Manager, Traffic and Police Departments should analyze the crashes on Cambridge streets that already have quick-build cycle lanes to determine if there are any hazards in the new design that can be mitigated on those streets and in future installations.
The number of crashes on two streets in Cambridge with the longest experience with quick-build lanes clearly indicates that the new design is not a cure-all for pedestrians or cyclists and that there are enough data for qualified staff to determine crash rates as well as any changes in crash severity. It’s their job, not mine.
Chris Cassa, jkang, WilliamF., Itamar Turner-Traurig, GB, cwec, alexw, AvgJoe, nkauf, CH39, DWY333, Jan Devereux: If you truly care about safety, why do you object so strenuously to my proposal? Are you afraid of the results of the kind of review I am asking for?
@John, there was a major federal safety study released last year, conducted by professional transportation analysts. It used data from bike lanes in Cambridge (including the lane you cited on Cambridge St.) The result is (unsurprisingly) that bike lanes reduce crash rates. The safety benefits of changing from a painted bike lane to a separated bike lane are substantial (53% reduction in crashes) and statistically significant.
https://highways.dot.gov/safety/proven-safety-countermeasures/bicycle-lanes
Cambridge Day used the correct procedure by printing the letter (uncensored) and printing responses (uncensored). I found the letter and responses informative for me as an 80 year old adult who has no choice but to drive while respecting the rights and safety of cyclists and pedestrians.
Cambridge Day’s own standards are that published letters must be “fact-based.”
This isn’t. I disagree that it is the correct procedure to publish lies and expect the public to fact check them.
@John Pitkin
Your letter is propaganda. Your data analysis is flawed because it uses the wrong measures. Anyone familiar with analyzing crash data knows that crash rates, not raw crash numbers, should be used. Your data selection is so selective it appears cherry-picked to support your desired conclusion.
Federal scientists have analyzed the same data and found the opposite: bike lanes dramatically reduce accidents.
You either don’t understand what you are doing or you do and are being deceitful.
The city has many experts in data analysis, but you are not one of them.
@Gerald Bergman Cambridge Day did NOT use the correct procedure. These letters are supposed to be fact-based. John Pitkin’s letter is not. It has been contradicted by professional researchers who actually know what they are doing.
Clearly, Cambridge Day does NOT have a procedure in place to ensure that letters are fact-based.
John, it’s not that we’re “afraid” of the results of properly studied data–those results already show that separated bike lanes improve safety for all road users.
What we’re actually afraid of here is more people injured on Cambridge streets as a result of a delay, because everyone here knows that you’re a bad faith actor that has attempted to use the courts to remove all of the CSO quick build lanes in Cambridge, and that you’re working backwards from a conclusion to find a reason to delay these lanes further.
@cwec Exactly. John Pitkin’s flawed, half-baked analyses show all the signs of someone deciding on a conclusion and then manipulating the data to fit. That’s not how data analysis works, John.
We already know that Cambridge bike lanes reduce accidents—a federal study proved that. You’re just fabricating nonsense because you dislike bike lanes.
Are you afraid of losing some parking? Your advocacy will lead to preventable accidents, all because some people prioritize their own convenience over others’ safety.