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Canadian study: On residential streets, traffic diversion is key for safe cycling

From a Cycling in Cities presentation at Velo-City 2012

The University of British Columbia cycling safety research group Cycling in Cities presented the Velo-City 2012 conference with some fascinating studies on the relative safety of urban cycling infrastructure in Canada. Their findings could be extremely useful as the city updates the Bicycle Master Plan and attempts to take the first steps in creating a network of neighborhood greenways.

One big—and somewhat surprising—find is that traffic circles scored very poorly. Seattle has invested heavily in residential street traffic circles, which are proven to reduce traffic collisions and slow motor vehicle speeds without the negative effects of having too many stop signs (the more seemingly pointless stop signs you have in a traffic system, the more people tend to roll or ignore all stop signs, which is bad).

However, while traffic circles might work well at reducing car collisions, the BC study suggests that people biking do not fare as well. Traffic circles have been at the heart of the debate between SDOT and many neighborhood greenway advocates, who want to see stop signs for residential streets that cross a neighborhood greenway. SDOT has maintained that traffic circles are an acceptable treatment and do not want to add the signs. So this study could give greenway advocates a push in making their case.

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The best scoring factor for safe neighborhood streets in the study is traffic diversion (1/20 the risk compared to no infrastructure). Fewer cars means better safety for people cycling, so constructing barriers to reduce through traffic makes the street safer. All points on the street remain accessible to people driving, but anyone traveling more than a couple blocks should be required to take other streets (preferably, a nearby arterial street).

These findings suggest the city may have missed some opportunities with the Wallingford neighborhood greenway on N 44th/43rd Streets. All intersections along the route are controlled by traffic circles (preexisting) without stop signs, and the city scaled-back a traffic diverting crossing at Stone Way to allow motor vehicle turns and through traffic movements.

This isn’t to say the Wallingford Greenway is a failure or that SDOT’s trust is traffic circles is misguided. Our neighborhood streets are very skinny, and car speeds are very low (another very key factor in cycling safety). It’s not clear how our street conditions compare to those studied. But we should be looking for ways to make each neighborhood greenway we create better than the ones before it. Projects due to be completed this summer include neighborhood greenways on Beacon Hill, NE Seattle and West Seattle.

Other findings in the study suggest that cycle tracks are, indeed, extremely safe (1/20 the risk compared to no infrastructure). We should be installing them as our go-to piece of infrastructure on high traffic streets. Bike lanes are slightly safer than nothing, and sharrows actually scored worse than no infrastructure at all.

As Portland planner Roger Geller reportedly said during a Velo-City presentation, “Just use the hammer.” Protected bike facilities are clearly the best, and they should be used in nearly all arterial street situations. This should be a key tenet in the new Bicycle Master Plan.

Perceived vs Observed Risk

Cycling in Cities also presented on the relationship between perceived risk and observed risk for cycling facilities. Their findings suggested that people have a pretty good idea of which facilities are dangerous.

However, people studied suggested that they felt cycle tracks are more dangerous than they actually are. They also thought multi-use trails (where people biking mix with people walking, roller blading, etc) are safer than they actually are.

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21 responses to “Canadian study: On residential streets, traffic diversion is key for safe cycling”

  1. Leif

    Very interesting. My route to work from Greenwood down 6th contains many traffic circles and a few unregulated intersections. I routinely observe cars and bikes flying through the unregulated intersections as if nobody could possibly be coming in the other direction. I feel very unsafe at those. The traffic circles have the (theoretically) beneficial forcing function of making everyone slow down a bit and I certainly feel safer on them than with nothing at all. I guess that is an example of perceived risk being lower than actual.

  2. LWC

    Most interesting to me: they found that a major street with no bike lane is actually slightly safer than a multi-use path, as long as there are no parked cars. A support for vehicular cycling?

    1. Tom Fucoloro

      Note that their definition is “multi-use path” seems to be more like a pedestrian plaza space than something like the Burke-Gilman Trail (which they just call a bike trail). See the images they use in the report to get an idea of what I mean.

  3. […] the rest here: Canadian study: On residential streets, traffic … – Seattle Bike Blog This entry was posted in Blog Search and tagged cities, city, columbia, conference, presentation, […]

  4. phillipb

    I have, on several occasions, nearly been creamed by cars taking traffic-circles clockwise, i.e. the very dangerous 1/4 way ‘round left-turn shortcut. I have even been overtaken by cars speeding through circles down the wrong side as if the intersection were merely some bulbous passing lane.

    Combine motorist impatience and ignorance in negotiating traffic-circles with the impeded sight-lines of many of the more flowered-&-forested circles and I can see why they are statistically more hazardous to bicycling than one might initially assume.

  5. Doug Bostrom

    I wonder if by “traffic circle” the study looks at real traffic circles on arterials etc.? There are very few intersections in Seattle w/traffic circles that would be recognizable as such by people living in countries where circles are the norm.

    1. Orv

      I wonder that too. In most countries a “traffic circle” is what we call a roundabout — e.g., one that’s large enough to circumnavigate in one direction no matter which way you’re turning.

      I think the mini-traffic-circles we have here that allow for clockwise left turns are a bad idea, but they do slow down traffic.

      It would be interesting to see how traffic diversions affect emergency vehicle response times, compared to traffic circles.

    2. Tom Fucoloro

      The photos they use in the report shows traffic circles on residential streets (they also make references to them as residential street features). They do not seem to discuss roundabouts in the report.

      The question is: are their streets as skinny as ours? Do they have parking on both sides of the street? Do they have strict landscaping rules like Seattle supposedly does (though they are not always followed) to prevent sight-blocking plants? How far from the corners are cars allowed to park? These are all factors in the safety of them.

      But it looks a bit doubtful that they could be considered GOOD for cycling…

      1. S. Morris Rose

        In Vancouver, cars are required to park 6m from an intersection. However, it’s not well-known- it’s not posted on stop-signs, for example- it’s lightly-enforced, and it’s therefore not widely observed. In Seattle, the rules are both widely publicized *and* widely ignored.


        Residential streetwidths in many Vancouver neighborhoods are similar to those in Seattle neighborhoods, perhaps slightly narrower. What’s different is that most neighborhoods have lanes with unattached garages off the lane. That makes for many fewer curbcuts for driveways and many fewer conflicts with vehicles entering the roadway mid-block. Also to many fewer cars parked across sidewalks. That would seem to make a sidewalk a great place to ride a bike in Vancouver, but it’s not legal for adults to do it.

  6. GordonofSeattle

    Thanks for the clarification Tom I was really scratching my head at the risk of multi-use trails.

  7. ODB

    My understanding of the study’s methodology is that for each injury, it compared the injury site with two randomly-selected “control sites” that the rider passed by without incident before the injury–deeming the random sites to be safe.

    Unfortunately, there is not a lot of explanation of how the analysis was done (and I might not have understood it anyway), but it seems to me that the types of infrastructure most-extensively used by cyclists, whether they prefer it or have no other choice (such as streets with no bicycle improvements or intersections with traffic lights) would be more likely to be selected when randomly locating the “safe” control points than infrastructure less-commonly chosen or encountered by cyclists (like sidewalks and traffic circles).

    In other words, unless the study corrected for the the cyclist’s degree of exposure to a given piece of infrastructure, it would seem to be biased towards randomly selecting the most commonly-used pieces of infrastructure as relatively safe.

    Would that help to explain the poor marks given to traffic circles–perhaps a relatively rare piece of infrastructure in Vancouver and Toronto–which otherwise seems like an anomalous result (8 times as risky as traffic light)?

  8. I’m a bit surprised by the traffic circle result, too. Traffic circles seem to create order at uncontrolled intersections. But collisions are exceptional events, and maybe it’s more common for people to commit severe errors at them (like driving the wrong way through them, which should be flat-out illegal… if your car can’t make the turn the right way, turn somewhere else).

    Some of Kirkland’s residential areas have traffic circles, but with much wider residential streets than Seattle has. A driver and cyclist can travel side-by-side until they approach the intersection and are then forced together (this is a problem with other sorts of traffic calming as well, including sidewalk bulbs for those cyclists that prefer to ride in shoulders and empty parking spaces). I wonder if this is common in Vancouver and Toronto. The section of the Lake Washington Loop west of the Arboretum has this problem in some places — I’ve seen drivers pull out as if to pass me (this should be illegal on any street with traffic circles, including this route), then realize they have no place to go and stop. My guess is that the traffic circles along most Seattle side streets (like those used by the Wallingford Greenway) are much safer, since nobody is actually going to get beside you there (anyone that does deserves something harder than a traffic ticket going through his windshield) but obviously I don’t know for sure, and of course SDOT fouls up the whole thing by encouraging cyclists and drivers to get parallel at other intersections.

    Of course, this whole study ignores the details of design and questions of practice. A shoulder re-painted as a bike lane doesn’t magically attain the benefits of a bike lane, and a sidewalk re-painted as a cycle track doesn’t magically attain the benefits of a cycle track. And as far as practice goes… collisions are exceptional events. The difference between the best and worst cyclists is greatest on the worst infrastructure, and the difference between the best and worst infrastructure is greatest for the worst cyclists. Follow good practices and your odds are better than the printed numbers by a lot. A good cyclist may face increased risk at traffic circles because of idiot drivers going the wrong way, but probably isn’t 8 times more likely to be injured as at other intersections.

  9. Breadbaker

    I’m familiar with neighborhoods in Vancouver that are set up essentially so that you can’t drive more than a block without turning onto a side street, but which include an express throughway for bikes. Not surprisingly, these are quite a bitch to drive and quite a wonderful thing to bike through. Essentially there is a curb with a sidewalk-sized cut for bikes, wheelchairs and pedestrians. That these would be more safe than a traffic circle is no surprise. There is generally good visibility as you bike through to the other side (where traffic is turning the other way). The key, though, is that there is no way for a car to do anything but turn while the bikes are going straight.

    General impression, and obviously I haven’t biked all of Toronto though I’ve biked a huge part of Vancouver, is that residential streets are wider and if there are traffic circles, they’d be on streets that are less calmed between the intersections than 44th and 43rd in Wallingford. I also have the impression, and it is only an impression, that the traffic diversions are not an infrastructure that is intended for bikes, but to keep through traffic out of the neighborhoods.

  10. basketlover

    I dig the “chicanes” that let just one lane through at a time.

    1. The instances of these I’m aware of are: NE 70th St east of Roosevelt Ave; somewhere along 19th Ave; and on the Lake Washington Loop route west of the Arboretum.

      The ones on 70th are really substantial; they seem to be pretty effective at deterring all but the most necessary car traffic east of them. The ones on 19th also seem somewhat effective; they’re south of one of the arterials, and south of there there’s considerably less traffic to deal with than north of there… but, then, north of there it’s designed much more as a through-route and commercial street. The Lake Washington Loop ones are more troublesome. They seem designed to slow drivers down, and make everyone get serial through intersections, and that works as long as the drivers are cooperative. Drivers impatient about passing would create conflicts on that route with or without these minor calming devices, but the devices seem to prolong the conflict.

  11. Edmonds cyclist

    Interesting to come across this study, as I’ve just moved to Interurbanland and gotten an up close and personal experience with riding through areas regulated only with traffic circles/roundabouts where the Interurban route continues through North Seattle. It made me nervous. I was surprised at the amount of vehicle traffic cutting through from Aurora at every other street or so, and wondering why we have to have all these perfectly gridded, connecting streets one after the other. Apparently it’s not too difficult to fly around a traffic circle way above the posted speed, and many of the drivers I encountered looked surprised to see someone on a bike (panic stops and then yielding or zooming on through). I’d much rather be on a major arterial with signs/lights because I feel like I can better predict dangerous situations than having to frantically look 3 different directions with limited sight lines.

  12. lunatiki

    I couldn’t agree more about Fremont south of 105th. That area always feels like the most dangerous part of my bike commute. The city’s idea that having bikes on a designated street would help slow drivers down because the drivers would anticipate the cyclists is a bunch of rubbish.

  13. merlin

    Having just spent 4 days riding back and forth on one of Vancouver’s neighborhood bikeways (Ontario, from Langara to downtown, for those who know Vancouver) I can say that the traffic circles differ from ours in several ways. First, Ontario is quite a bit wider than our residential streets, so even though cars have to deal with diverters, traffic circles and bike-prioritized stops (I don’t know the technical term), parked cars don’t serve as additional traffic calmers and cars can move pretty fast despite the 30 km/20 mph speed limit. Second, the traffic circles are all signed with arrows indicating that you’re supposed to go around them on the right, and I didn’t observe anyone cutting corners on these like they do in Seattle. The vegetation in the circles does not include trees but can still obscure oncoming cars. Traffic volumes were very low on the whole length of Ontario when I rode it, early morning and evening.

  14. But even “bike trails” didn’t score anywhere near as well as the vehicular diversion options. Before I came to SBB, I thought of bike lanes and cycle tracks (and even sharrows) as the “freeways” of the non-motorized transportation system, with multi-use bike paths being more like Aurora (besides the pedestrians, you also have to cross sidewalks and connections from businesses and homes).

  15. Okay, this is weird. When I hit reply in Chrome, I get returned to the top of the page, and then it doesn’t post as a reply even though I know for a fact it looks for all the world like it’ll post as a reply.

  16. As a UK resident, I know precisely why traffic cycles are dangerous. They encourage drivers to come on at speed rather than to a complete halt.

    Here’s a video of a journey I’m doing with my son on a quiet holiday morning -I pull ahead of him to be more visible to the car you can appear approaching on the left.


    If you look at the video, you can see the driver shoots past without apparently looking, about the same distance from my front wheel as Cavendish beat Grimpel today. You don’t see the driver looking vaguely apologetic as he did so.

    This video was enough evidence to get the driver to plead guilty to driving without due care and attention, a £400 fine and penalty points on his license. He did still try and hide from owning up to it for six months -the police had to tag his numberplate as one of the cars the police should pull over if it went past and their automatic plate recognition system saw it.

    This is why lights are safer than circles -at least in the UK when vehicles cannot turn if they have a red light. In the US you have to worry about vehicles turning over you at any time

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