Study: Sharrows Don’t Make Streets Safer for Cycling

Sharrows are the dregs of bike infrastructure — the scraps cities hand out when they can’t muster the will to implement exclusive space for bicycling. They may help with wayfinding, but do sharrows improve the safety of cycling at all? New research presented at the Transportation Review Board Annual Meeting suggests they don’t.

Sharrows are useless and perhaps even harmful, a new study found. Photo: University of Colorado Denver
Sharrows without traffic-calming won’t do much to make cycling safer. Photo: University of Colorado Denver

A study by University of Colorado Denver researchers Nick Ferenchak and Wesley Marshall examined safety outcomes for areas in Chicago that received bike lanes, sharrows, and no bicycling street treatments at all. (The study was conducted before Chicago had much in the way of protected bike lanes, so it did not distinguish between types of bike lanes.) The results suggest that bike lanes encourage more people to bike and make biking safer, while sharrows don’t do much of either.

Ferenchak and Marshall’s study divided Chicago into three geographic categories using Census block groups: areas where bike lanes were added between 2008 and 2010, areas where sharrows were added, and areas where no bike treatments were added. They then looked at how bike commuting and cyclist injuries changed in these areas over time.

They found that bike commute rates more than doubled in areas with new bike lanes, compared to a 27 percent increase in areas with new sharrows and a 43 percent increase in areas where nothing changed.

Meanwhile, the rate of cyclist injuries per bike commuter improved the most where bike lanes were striped, decreasing 42 percent. Areas that got sharrows saw the same metric fall about 20 percent –worse than areas where streets didn’t change (36 percent), although the difference was not great enough to be statistically significant.

One caveat with the study is that measuring bike commuters who live in a given area is not the same as measuring the number of people who actually bike on those streets. Still, the results strongly suggest that sharrows are ineffective as a safety strategy.

Ferenchak told Streetsblog sharrows seemed to have a small effect on encouraging people to bike but provide no additional protection. This is in line with what Dutch bike planner Dick Van Veen told Streetsblog about sharrows in the Netherlands: They should be used in tandem with significant traffic-calming measures — on a street with fast traffic, to put down sharrows alone would be considered “unethical.”

“I think our main takeaway is that we need appropriate infrastructure,” Ferenchak said. “Sharrows don’t dedicate any space to bicyclists.”

145 thoughts on Study: Sharrows Don’t Make Streets Safer for Cycling

  1. only in your dream world. building more paths doesn’t equate to more people riding. your ignorance is showing.

  2. Our motorized vehicle infrastructure was and is politically driven to encourage automobile use. Turns out there are some problems with that. There is no earthly reason not to give bicycle use a reasonably proportionate fraction of the resources that are poured into automobile infrastructure. Bicycle infrastructure is relatively cheap, and cycling has a lot of positive side benefits.

  3. Fact check: as a gun owner for the past several decades, the NRA doesn’t represent me; they’ve transformed themselves from a national advocate for gun safety to a fringe group of hard-liners. They definitely don’t “represent every level of user.” Indeed, the overwhelming majority of American gun owners oppose the NRA’s positions on issues like background checks.

    Don’t assume there’s consensus just because you don’t see the dissent.

  4. Cyclists can have very different opinions of sharrows depending in part on how their local sharrows have been installed — this, for example, is taken from an official Seattle DOT explanation of how sharrows work, and accurately represents how SDOT installed sharrows for many years.

    SDOT openly advocated that sharrows would encourage cyclists to ride in the door zone of parked cars, so that motorists could squeeze through in the same lane with less than two feet of clearance.

    That’s how they installed them, and that’s how drivers interpreted them.

    It took City Council intervention with a mandatory policy of centering sharrows in the travel lane to get SDOT to abandon this practice, but the vast majority of Seattle sharrows are still in the door zone, and SDOT does not intend to correct them until they’ve worn out.

    If you’re a Seattle cyclist, and this is your experience of sharrows, you’re likely to think they’re worse than door zone bike lanes.

  5. Strava heat maps are incredibly biased. They primarily represent the route choices of tech-savvy middle- and upper-income cyclists with competitive aspirations.

    The highest concentration of bicycle commuters in my town is a large apartment complex, not surprisingly, since data consistently show bicycle commuting is highest among the lowest income groups. Visual observation confirms many of these people bicycle for transportation, and Google Earth images clearly show the “desire lines” of bicycle travel through unimproved shoulders just outside the complex.

    Strava shows lines of blue on popular recreational routes on every side of that area of apartments, and not a single blip of blue anywhere within the blocks of apartments.

    Strava is a handy tool when engineers say “nobody rides there”, but they’re a lousy tool for identifying where utilitarian bicycling currently takes place.

  6. I would hesitate to claim that sharrows are 100% effective for the people who choose to use them.

  7. Funnily, cycling instead of driving your car is fixing some problems. Smog, for example. Traffic jams. It’s also healthy, thus lowering the overall cost of a social health insurance. Sure, it’s not going to fix the world, but neither does your prejudice.

  8. You may be correct, Josh, but it doesn’t change the fact that bicyclists miserably suck at working together for their own common good. There are many examples of orgs that have a large tent, and everyone is covered by it, and they get lots done. As long as LAB continues promoting only bike paths and protected bike lanes, and the “Bicycle Drivers” remain steadfastly against on-road safety and infrastructure, we’re going absolutely nowhere (yes, there are even bicyclists who oppose legislation such as the Vulnerable Road Users law – based on inequality – even though said laws have resulted in stiffer penalties for the motorist at fault).

  9. I’ve read the study, although it was a difficult exercise. Why? Because the “nonsense” frequency gave me a headache from all the eye-rolling I did!

    Example: The authors begin by claiming the only initial motivation for sharrows was to reduce dooring. That’s absolutely false. They then claim that dooring is a rare problem, despite saying that in Boston, doorings were 11% of car-bike crashes, and 29% of bike messenger-car crashes. Other sources say 20% of Chicago bike crashes are doorings. Those numbers don’t qualify as “relatively rare and benign.” And the author’s polemic question, “Why would we install sharrows that avoid doorings at the cost of of increasing risk for vehicle collisions?” is nonsense, because it displays the author’s hidden assumption that riding more prominently in the lane increases risk of collisions. Most truly competent cyclists have found the opposite to be true, and _that_ is a major point of sharrows!

    Another example: The authors then suddenly switch to claiming that the intent of sharrows is (instead?) to increase passing clearance by cars. They claim the results are “highly variable,” but cite several studies in which that spacing was, indeed, found to increase, by anything from several inches up to 2 feet. They also mention studies correlating sharrows with less sidewalk riding, greatest benefit on four-lane roads, etc. Yet they disparage sharrows as ineffective.

    It’s significant that the paper does not ever count actual cyclists using actual sharrows! (Nor bike lanes, nor plain streets, for that matter.) Instead, it uses approximate data on bike _commuting_ as a proxy for total ridership. And it generates its risk ratios by using _all_ cyclist injuries. In other words, a wrong-way midnight drunk’s crash is divided by the number who claim in surveys to be commuters.

    And not the number of commuters on the street where the drunk crashed! The authors use approximate data on city “block areas” of unspecified size. If a “block area” has some streets with nothing special and one street with a short section of sharrows, it apparently counts as a sharrow “block area.” Furthermore, the before-after computations that purported to evaluate the cycling treatments don’t use even the same “block areas.” Those boundaries shifted over the study period, so the areas are only approximately similar.

    Given all those shortcomings: What the authors actually found was that “block areas” with sharrows saw an increase in bike mode share (based on surveys, not on observation) from 0.69% to 1.32%. As with “block areas” with no changes (0.33% to 0.75%) or those with bike lanes OR recreational bike paths (0.64% to 1.78%), those changes might best be characterized as “from negligible to negligible.” However, all are increases.

    Likewise, the injuries (of _all_ cyclists) per 100 bicycle commuters dropped from 33.3 to 21.1 for no treatment, from 31.2 to 25.1 for sharrow-containing “block areas,” and from 59.2 to 34.4 for bike lane “block areas.”

    Now think about those magnitudes. 59.2 reported injuries for every 100 bike commuters! How can that be? Again, its’ _all_ reported bike injuries – the drunks, the kids falling off their bikes and rushed to ER by helicopter parents, the wrong-way-sidewalk riders, the stunt riders and more. It makes sense only because the commuters are a negligible portion of the total – yet that negligible portion is used as a denominator in evaluating safety. The logic is mathematically weird.

    Note that the sharrow “block areas” did experience an increase in cycle commuting, as well as a decrease in (computed) crash rates. How, then, do the authors justify their statement that “sharrows have less than desirable outcomes”?

    The authors do a fair job of listing the shortcomings of their methodology: the assumption that the impact of bike infrastructure would be experienced _thoughout_ a “block area” if any street gets some bike facility; the assumption that bike commuter survey responses accurately indicate _total_ bike use. They admit that the proper way to evaluate both ridership effects and safety effects would be by accurate before-after counts, but say they chose their strange methods because – well, because it was easier to get this data!

    But they also hint at perhaps the biggest shortcoming: the implied direction of causality. The entire paper implies that the bike lanes _caused_ more increase in cycling than the sharrows, and _caused_ greater increases in safety. Segregation-promoting websites like Streetsblog have certainly taken up that cry. However, four paragraphs before the end, they say “the results of this research do not imply causality…”

    Right. In effect, its an admission that their paper’s message is not justified by their own data, as weak as that data is.

    To explain: There could be many undetected or ignored confounding factors behind the data. Did bike lanes increase cycling more where they were installed? Or were the bike lanes installed because those “block areas” had lots of cycling, good cycling conditions and lots of commuting potential via short trip lengths, hip local culture, accommodating businesses, etc.? Did those already cycling, and right on the edge of commuting, demand the bike lanes? Would the commuting have increased just as much during this period of growing bike fashion? We don’t know; but it would not be at all surprising if DOTs installed bike lanes where cycling was growing the fastest and requested the most – in other words, where cycling was already pretty good.

    Finally, the authors tip their hand in their final three paragraphs. These young research assistants in Denver constructed this paper because, according to them, Denver is on track to completing its planned sharrow installations, but it is “falling behind” on other facilities. (Yes, gentlemen, installing any bike lane, especially a “protected” one, is more time consuming because of the need for acquiring and clearing right-of-way, or studying the effects of reducing traffic lanes. Separate bike trails are even more complicated. Who could be surprised that sharrow installation happens more quickly?)

    Here’s their final polemic: “It is time that sharrows are exposed for what they really are, a cheap alternative that not only fails to solve a pressing safety issue, but actually makes the issue worse through a sense of false security.”

    That’s what I call a “Danger! Danger!” argument. “Oooh, riding a bike is SO risky that it’s a pressing safety problem!”

    Let’s keep in mind that data shows Americans ride over 10 million miles per year between fatalities. And that, per mile traveled, those walking experience three times as many fatalities as those riding bikes. Those numbers, BTW, come from John Pucher, who – despite the data’s message – is another “Danger! Danger!” proclaimer regarding bicycling.

    It is flatly anti-cycling to exaggerate the danger of bicycling, and to claim that one dare not cycle until one has completely segregated infrastructure. It suppresses cycling here and now, and tends to blame those few victims who are injured while riding legally, using their rights to the road. “Advocates” of that stripe need to be exposed for the fear mongers they are.

    Meanwhile, the main benefits of this paper are exposing those who buy its message. They place themselves firmly in the fear-mongering camp, and illustrate their gullibility and their bias.

  10. That’s interesting. I wrote the author and asked for a copy to read myself. He said it was in peer review and couldn’t be distributed just yet. Obviously, it had been distributed so the answer wasn’t plausible. Nevertheless, thanks for this great analysis.

  11. Agreed. I have seen some terrible examples, the last being door zone sharrows in Pittsfield MA. I was shocked to see it, because this would never happen anywhere in the State of Delaware. A memorandum from DelDOT (who controls 90% of all roads in the State) limits them to 25 mph multi-lane zones, 14′ from the edge line or curb which places them in the center of the lane.

    As for checking the box, my example in Newark is anything but. It’s a 2 lane, one-way road through a downtown, with space only for cars and parallel parking. Sharrows combined with BMUFL is the last, best, and only treatment available. The rest of the City is balanced with a wide array of treatments, depending on available ROW, VMT, and other factors.

    DelDOT has its problems, but they’re working through them on the input and advice of advocates. This means sticking to AASHTO guidance as well as developing new treatments that are a hybrid of dedicated space (shoulders/bike lanes) as well as full lane control at intersections. Maybe some of the time people spend commenting on these pages should be spent advocating their own DOTs to do the same.

  12. I have yet to meet a bicycle driver who is against on-road who is against on-road safety and infrastructure and I know a heck of a lot of them.

  13. I wouldn’t assume some of the above are bicyclists. At least one just looks like a hater trying to spread his ignorant views.

  14. My being lawfully *in the way* of motorists does make some of them angry. I wish that wasn’t their reaction; I don’t ride to cause problems. Sharrows can inform motorists that bicycling is allowed and intended *in the way.* Calif. has modified their MUTCD to allow use of Sharrows on roads with posted speed limits higher than 35 – where bicycling is not prohibited and no Bike Lane, Bike Path, or Cycle-tracks is avalable why not inform motorists that people bicycling may be present? Really.

  15. Still waiting to hear Angie Schmitt’s review of the study itself. May I share some statistics from the study that weren’t in the abstract? According to their data, which I think is flawed because they use census data for cyclist counts (which is number of census takers whose primary mode of transportation to work is bicycle), the injuries per year per 100 cyclists is 34.4 for census blocks with primarily bike lanes, 25.1 for census blocks with primarily sharrows and 21.1 for census blocks with no bicycle infrastructure. Think about that.

  16. May. “Must” wouldn’t be appropriate, really. There are times when it’s appropriate to move over and let cars pass. We have some long stretches of parallel parking that are often times not occupied, opening up what appears another whole lane. Even though there’s sharrows, better to use that and let cars pass.

  17. Well, that is the clear impression one is left with. I challenge you to read any of their pages or forums, and see if you can glean what they are actually in favor of. There is the very occasional mention of a “good” bike lane, for example, but never do they define what exactly that is, or what they see as acceptable for on-road infra. Even Sharrows draw the ire of some. Most everything discussed revolves around how horrible everything is. Even the Vulnerable Road Users Law somehow became offensive, because it suggests inequality (I swear it was on a page I was reading, probably “Bicyclists Belong in the Traffic Lane”).

    The other problem I have with these groups is, they love to complain, but rarely – if ever do they advocate for whatever it is they do want. Every time I pose the question “have you taken the time to know your legislators, DOT planners & engineers, your MPO (if you have one) and work with them to implement properly designed infra”. Or if you can’t do that, join your local or state advocacy org and demand that they do. When these questions are posed, it’s the last comment of the thread.

  18. I wouldn’t count on Angie’s, or LAB’s support for anything on-road infra, Khal. Both are under the delusion that someday soon in the U.S., there will be bike paths for everyone, everywhere; roads need not apply. We’re having the same problem with our own State’s advocacy org (DE), that actually sabotages efforts at on-road safety and infra because they see it as a “threat” to the existence of separated pathways. They’re afraid it will provide our DOT with an out not to build any, because something was already provided on the road. They are the extreme opposite of the Bicycle Driving movement, in that every road = bad. Again, this is why bicycling advocacy in the U.S. is all but useless, ineffectual, and simply cannot organize itself. In the U.S. – especially in its suburbs – there are so few ROW opportunities for pathways, that this very notion is ludicrous, laughable. In the cities, narrow streets are all you have most of the time. So how these people think we can eliminate roads someday, I will never know.

  19. The article is my review of the study. Are you saying the author of the study misinterpreted his own findings and that both the Transportation Research Board and I failed to notice it? I think it’s more likely that you made a mistake reviewing and interpreting it. I don’t have time to respond to every comment in this thread. But defend sharrows all you want if you like them. It’s just one study. The author acknowledges there are limitations.

  20. “…Here’s their final polemic: “It is time that sharrows are exposed for what they really are, a cheap alternative that not only fails to solve a pressing safety issue, but actually makes the issue worse through a sense of false security…”

    An unbiased study should not have such statements. That sends up a big red flag.

  21. The problem I see with sharrows is that most people don’t know what they are for. They assume that they just mean there might be a bicycle on the road, rather than to indicate the safest place to ride. Even with them, cyclists continue their own bad practices. On top of that, they are usually on the busiest streets (because that’s where they’re needed). Crashes on those streets will naturally be higher.

  22. I believe that the methodology of the study was flawed because it compared census block groups rather than specific streets with infrastructure. Also, I don’t think census takers who use their bicycle as their primary mode of transportation is a good measure for ridership. Does a census taker bicycle only in their census block? Of course not. When I asked how the author derived the numbers of crashes per 100 cyclists, he told me that the data for those statistics was for a different period than the data for the injuries per year per block group and he said it was confusing. Yes I do question the data. I’ve said it before and I’ll say it again. Studies about bike infrastructure should be looking at before and after cyclist counts and crashes on the street with the infrastructure. I am not saying that sharrows are safer than bike lanes. But I am saying that sharrows increase ridership and decrease crashes, and are a good choice for streets that are appropriate for cycling to guide cyclists to proper lane position and educate motorists that we belong on the roadway.

  23. I am not going to explain where my point of view comes from, but I know exactly how and whey the data that you cite is gathered. I also know exactly what the figures are. I also know how few are using this infrastructure for commuting to work type purposes. Sure, using your bike in NYC or Vancouver to get around and pick up groceries is smart. I am all for that. But to believe that you are somehow going to fix our future by eliminating lanes on the road way or creating more connection paths is going to be cost effective…you are frankly dead wrong. Bicycles are not new. I rode one plenty when I was a child. I rode it to work, I rode it to the store, etc. I ride one when it is necessary or makes sense today. However, I also didn’t demand gutting infrastructure or believe I was saving the world. I got along just fine without a care in the world to what kind of nonsense the cycle nuts spew. The costs do not justify the means….and the whole build it and they will come idea is a net loss for communities by and large in real $$. It is never going to be practical to expect Mom to drop off her kids at school on her bike. Or a business man taking his bike to a meeting only to dust off his suit. The real problem with traffic is commuter traffic and that will not be answered by people getting on a bike.

  24. Holy thread resurrection, Batman!
    Looks you spent 22 days trying to come up with a rebuttal, which is basically a wordier re-statement of your original, evidence-free opinion. Sad.

  25. Ever see one of those photos of a Dutch train station, with several thousand bikes parked outside?

    You know what the U.S. Census would tell you about those bikes?

    None of them are owned or ridden by bicycle commuters, because they only rode them to the train station — they’re transit commuters.

    Any study that uses Census counts of bicycle commuters as a proxy for cycling exposure has already made a fatal mistake.

  26. We use sharrows where we don’t have the room to do anything else. If the study shows a 27% increase in ridership that is a significant improvement – much better than nothing at all. Sharrows are inexpensive and are politically acceptable. Yes, other treatments likely to more, but cost more and require more space. The study shouldn’t be interpreted to say sharrows are worthless. They are a tool to use where nothing else fits. And we use them not expecting too much. Greenback sharrows are likely more effective and are a tool to be used on busier streets.

  27. Let me explain the flaw in your logic: Currently we don’t have very much cycle infrastructure. If we were too add more, more people would ride. The same thing happens with cars. Countries without very good car infrastructure don’t have a lot of people who drive, such as in the Turkish city of Istanbul, where only 15% of trips are made via car.

  28. That’s not necessarily true. Infrastructure does not always increase mode share and usually doesn’t increase it by as much as infrastructure advocates optimistically predict.

    The Dutch didn’t get mode share from infrastructure. They got infrastructure from mode share.

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  30. Concur. When we installed sharrows on Coast Highway 101 in Encinitas, we also had Bicycles May Use Full Lane signs to help drive the point across. The sharrows have been extremely successful in the downtown area, with its diagonal parking.

  31. Let’s not make the perfect the enemy of the good.
    This “yaybikes” article offers a more balanced view.

    I love protected bike lanes as much as anybody, but it isn’t going to happen everyplace. If we insist on bike lanes instead of sharrows we wind up with inadequate bike lanes, which are worse than having nothing, especially if you live in a state (such as New York) that legally requires cyclists to be in the bike lane, and you have bike lanes that butt immediately up against parked cars. It means you have street markings that legally require that you ride in the door zone. How insane is that?

    Sharrows have not been on the scene as long or as broadly as bike lanes, so it’s to be expected that driver’s may not be as attuned as they should be. Also, it may mean that we haven’t yet discovered the right formula. On the section of my regular commuting route that has sharrows, they appear only at 100-foot intervals, so could escape the attention of drivers. How about shortening that interval to 50 feet, to make them more visible? How about making them yellow instead of white?

  32. You may want to take a critical look at the study. It was presented at a conference, never published, never peer reviewed and as far as I can find never recreated or reinforced by another academic study.

    The study was based on self reported crash statistics, and as you know these are underreported and unreliable.

    However, it seems that hipster publications and various other popular websites seem to think sharrows are useless, we are now quickly headed back to the precursor of sharrows which is nothing at all.

  33. The findings that streets with shared lanes had even less growing of cycle traffic and less decrease of injuries then streets where nothing had been changed, raises the question, in what types of streets shared lanes had been installed.

  34. And now in English 🙂 – The findings that streets with shared lanes had even less increase of
    cycle traffic and less decrease of injuries than streets where nothing
    had been changed, raises the question, in what types of streets shared
    lanes had been installed.

  35. It is an error that cycling on separate infrastructure were safer than mixed traffic, as most accidents accur at intersections. There the various modes of mix necessarily, and coming from a cycle track behind parking cars, you are not visible well.
    And separate cycling infrastructure can be more comfortable or less comfortable than cycling on the roadway.
    Where cars are congesting, cycle tracks can make cycling quicker, but on many crossroads cycling infrastructure (especially cycling traffic lights) impedes cycling. That’s an outcome that many peopla in the daministration consider motor traffic more important – sometimes in spite of cycling themselves.
    I live in Bremen that has twice as much length of cycletracks than Copenhagen.
    Bremen is one of those cities, where cycle tracks were built, because there were always lots of cyclists.
    Today it is normal that mothers carry their children to kindergarten by bike, often with a trailor. Though the model split of cycling is as low as about 26 % (Bremen has has an extension of 39 km = 24 miles), also a significant number of bankers cycle to work. ((A City where cycling bankers are almost dominant, is Parma in Italy))

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