Seattle’s Playful Traffic Circles Tame Neighborhood Streets

Seattle traffic circle 3

Last week, Dongho Chang, Seattle’s chief transportation engineer, posted a series of photos on Twitter of the city’s traffic circles. These neighborhood traffic-calming treatments are so charming, we had to post them here.

Seattle started installing traffic circles in the early 1970s, and now there are more than 1,200 throughout the city, says Chang. Seattle DOT’s traffic circle program typically adds them to intersections in residential areas with no traffic lights or stop signs, though some have replaced stop signs on low-traffic streets at crossings with larger streets.

The circles compel drivers to slow down while approaching intersections, and they’ve made a big difference. “They are installed to address angle collisions, and we typically look for two collisions within the past three years as a basis for considering them,” said Chang. A 1997 study by the city found that the traffic circles reduced collisions causing injury 97 percent and all collisions 90 percent.

Neighborhoods can request traffic circles from the DOT. Because demand is so high, the city prioritizes intersections with safety problems, Chang said.

Each traffic circle costs about $20,000 to design and construct. Crews remove pavement to allow street trees and other vegetation to grow from soil beneath the surface of the street. The city leads the process of landscaping, often in cooperation with neighborhood residents, which is why you see so many creative touches.

The result is an effective, practical, and beautiful way for cities to improve traffic safety on residential streets.

Photo: Dongho Chang, City of Seattle

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Seattle Traffic circle 4

Seattle traffic circle

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20 thoughts on Seattle’s Playful Traffic Circles Tame Neighborhood Streets

  1. Drivers may have to slow down but they don’t have to stop (when they replace stop signs). In any case I think these things are Great.

  2. I’m going to take a contrary opinion. These circles look nice, but they shunt car traffic at an oblique angle into the path of cyclists and pedestrians in the parallel crosswalks. This is basically the same problem mixing zones have here in NYC, where mediocre infrastructure fails in heavy traffic or only works when drivers are careful already.

  3. As someone who bikes and walks around these on a daily basis, they are life savers for the single fact that they slow drivers down. The mixing ends up being very predictable and slow and safe. The oblique angle thing is a non-issue. Since drivers are forced to slow down, they inherently become more observant of peds.

  4. Agree with most of what you said but it should be addressed that many of the traffic circles in neighborhoods without sidewalks are far too small to slow vehicles. I used to commute from Fremont to Shoreline everyday and the bike trip on Dayton Ave from 85th to 110th where I could meet up with the Interurban trail was always my most hazardous because the traffic circles did nothing to slow down cars that were cutting across side streets from Greenwood to Aurora.

  5. They are AWFUL. I have one right outside my front window and contrary to what Dongho says there are stop signs, which were installed as part of a Greenway (aka Sharrows that have mostly faded away).

    There are collisions constantly not to mention the constant sound of honking horns as nobody knows how to use them.

    Issue 1) How do you take a left turn? People who are familiar with traffic circles would go around the circle and turn right on the cross street. People who are not familiar with traffic circles will just turn left and “short cut it.” The answer? Both are right! They are treated as uncontrolled intersections by the city in which case whoever is in the intersection has right of way and everyone not in the intersection must yield.

    Issue 2) Pedestrian crossing. Most of these circles require a bit more right of way for the increased pavement that comes at the cost of any pedestrian markings and leaves pedestrians in a bizarre limbo over when and where to cross, especially when they don’t know where cars are coming from (see issue 1).

    Issue 3) Turning radius. Seattle is a city of big pickup trucks. They tend to run over our circle on a daily basis.

    Issue 4) Stop signs! No No No Never!

  6. “Councilman Steven Matteo and Borough President James Oddo asked the DOT to install stop signs but were told traffic circles were a better fit for the street.”

    I’m amazed that DOT didn’t go for a traffic light, their default. (Other cities remove signals, not add them, to calm traffic.) Could this be a turning point? (Too bad they nixed the raised crosswalks though–those would be useful in so many places.)

  7. Yeah, I’ve lived in 3 different places in Seattle in the past year, 2 of which had no traffic calming and and 1 with traffic circles at almost every intersection. I had a couple close calls with drivers blowing through uncontrolled intersections on neighborhood streets without the circles, and more careful drivers on streets with. Anecdotal evidence, I know.

  8. They’re called round abouts over here and there are road rules in every country/city/area etc – im pretty there would have to be road rules there somewhere – if there aren’t any road rules then perhaps lobbying for it and educating the public might see a change for the better!

  9. Well it was somewhat of a jokey comment, but how does the existence of new traffic circles prove that they won’t eventually be flattened by some asshole driver?

  10. The trick in these low vehicle volume streets to use curb bulb out at all streets feeding into the these circles. This accomplishes the desired effect of forcing cars and bikes to use these intersections in the exact same way, creating the same right-of-way situations for both. Additionally, the narrowing slows down car traffic and makes the crossing distance for pedestrians much shorter, keeping them in the danger zone for as short a time as possible.

  11. That’s a great point and should be noted the the outside curbs are just as important in this design as the inner circle. Your example highlights this perfectly.

  12. The data behind this is interesting. If these really do offer a collision reduction of 90%, how many collisions have been avoided per traffic circle implementations per year? If you factor the total cost of a single collision – property damage, insurance case work, police work, towing, medical bills, lost wages, federal and state disability, etc – it is possible that these things pay for themselves in in spades!

    Such an analysis is time consuming but it would be a great way for safe streets advocates to justify spending if the cost of dangerous streets was clearly explained. So, who’s up for it?

  13. Issue one: the same could be said of merging, braking, turning left on a green, etc. It’s a skill and knowledge we expect of drivers. No difference. In no situation are ‘both right’. There is a clear case of right of way here.

    Issue two: in the examples provided, the streets themselves have indeed not be altered other than placing the circle in the middle. Is there room to choke down the crossing further? Absolutely and this would be a welcome addition.

    Issue three: That’s exactly the point. To slow down drivers and force them to drive more carefully. If you can’t navigate the street, you are too big or don’t possess the requisite skills.

    Issue four: Where is there a stop sign at a roundabout?

    In general, you are making insinuation that these things are dangerous when the data and anecdote proves otherwise. Why?

  14. I don’t have as much hatred for these as Southeasterner, but I can back up that for some reason, Seattle does occasionally put stop signs with these. There is a set on NE 42nd St and 12th Ave NE. I’ve seen others around the city too, but I can’t remember where.

  15. Issue 1: You are incorrect. Both ways are NOT right. In Washington it is illegal to “shortcut” a traffic circle by turning left. You should have learned this when perparing to take your WA driver’s license test, Southeasterner.

  16. Issue 4: stop signs at roundabouts on greenways are great, because bikes don’t really need to slow down much (from 15-20mph) to go through an intersection with a traffic circle (and then accelerate on the other side). If bikers know cars coming from the sides will have to stop it makes the greenway a much better biking route. And I don’t find stop signs at traffic circles to be any problem at all as a driver.

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