The magic roundabout

Roundabouts are rare in the US (where they are called traffic circles), with traffic authorities favoring stop signs instead. Last year ago, I wrote about the so-called ‘magic roundabout’ in Swindon, UK that contains seven roundabouts looks incredibly complicated but apparently moves traffic through it very quickly and efficiently. In that post, I provided the graphic below but it does not fully capture the experience.

Andrea James says that roundabouts are better than stop signs and provides video of the actual traffic flow in the Swindon roundabout, that has seen only one fatal accident in the last five years.

But for the person navigating it for the first time, it may be a bit confusing as this video of two Finnish tourists narrating their experience suggests.


  1. machintelligence says

    I am not totally impressed with roundabouts for heavy traffic. I encountered one in Stratford upon Avon that essentially blocked the flow of traffic on one of the roads because there was never a break in traffic in the circle. Once in a while a car would turn out and a few cars could enter the circle from the minor road, but it really stalled traffic in one direction. A few years later I was back and found that there was now a traffic signal at that intersection.
    The seven circle one looks like a joke or an attempt at a world record.

  2. DonDueed says

    In my town, a problematic intersection was redone last year. It involves a 4-lane divided highway with on- and off-ramps for both directions, and four surface streets, two converging on either side of the highway underpass.

    The old solution involved a traffic light on one side of the underpass and three stop signs on the other (including a stop sign at the end of the exit ramp on that side). It was nasty, with complex crossing patterns and ambiguity regarding right-of-way. It was dangerous to negotiate, and at times the southbound off-ramp would back up all the way onto the highway and cause a hazard to the traffic trying to go straight through.

    The new pattern replaces the light and stop signs with two traffic circles (we call them “rotaries” in this part of the world), one on either side of the underpass. There are no signals or signs other than yield signs at each point of entry to the rotaries. So far it seems to be working well, after a period of adjustment.

  3. flex says

    Generally it seems that roundabouts work well for traffic but they can be difficult for pedestrians, and on occasion bicycles, to navigate. In a roundabout a pedestrian trying to simply cross one of the feeder streets must recognize that there is no message ever given to the driver that the driver must at some point stop. So in a busy roundabout not only does a pedestrian have to look for traffic entering the roundabout from the street they want to cross, but also all the other streets feeding the roundabout because the street the pedestrian wants to cross may also be where the driver wants to go. There are similar problems for cyclists.

    These problems are not insurmountable, but it tends to make roundabouts a better choice where there is little pedestrian traffic.

  4. OverlappingMagisteria says

    “Roundabouts are rare in the US (where they are called traffic circles)…” unless in you’re in New England where they are called “Rotaries.” Probably just to confuse non-locals even more.

  5. jazzlet says

    I’ve driven through the magic roundabout and for some one used to negotiating roundabouts it’s easy to use. Having heard about it I was a little apprehensive the first time I used it, but when it came to it it was so intuitive that I didn’t realise it was actually the notorious magic roundabout I was going through until I was already out the other side.

    In the UK in areas with heavy traffic the flow onto a roundabout may be controlled by traffic lights, full time or only at the busiest times.

  6. fentex says

    I like round-a-bouts, and they used to be very common where I live.

    But not so much now, many have been replaced by traffic lights -- apparently because when traffic flow increases from one direction it can dominate and become inefficient with the lower volume entrances blocked from entering.

    One big round-a-bout beside our large central park was recently converted to lights and I couldn’t figure out why as busy traffic from all directions used to move smoothly there -- until a friend (who lives nearby to it) explained -- it was too efficient, with traffic constantly moving through it was impossible for pedestrians to cross there at bust times.

    And as my city puts on events in the park (orchestras, food fairs, cricket matches, fireworks) and it contains sports fields, tennis courts, bowling greens and access to our botanical gardens there’s a lot of pedestrians likely to be about when something is on, along with traffic as well.

    jazzlet: In the UK in areas with heavy traffic the flow onto a roundabout may be controlled by traffic lights, full time or only at the busiest times.

    I recall one in Croydon that is a forest of traffic lights. It was a bit of a surprise when I came across it, but I cycled through it okay, twice.

  7. blarg says

    Unfortunately, they are building several roundabouts and proposing even more in this part of central Ohio.
    I can only assume they we are being subjected to them for one of the normal reasons engineers and planners follow fads. Perhaps it is the current sense of beauty in design, or the latest batch of graduates were taught romantically about them as some halcyon cure-all. Likely, the Vogon Planning Council currently green lights and provides matching funding for anything roundaboutish (they did the same thing for new schools that could double as prisons with minor modifications during Bush II). Or just maybe they are the preferred method for the next generation of robo-cars to deliver dissenters directly to the police station.

    They suffer from many problems.
    Drivers find them confusing, even after they have been around for some time. Older people especially seem to struggle greatly with them, preferring to stop and sit awhile until it makes sense to them.
    Visibility is another problem. Not only are you having to constantly keep your vision to the right for traffic while navigating to the left, but the towns here seem to like putting tall things about them, like statues in the center or ornamental grasses about the edges.
    When the mowing crews are out around them it is like playing Frogger getting through.
    And what a dangerous mess you find when it is time for clearing snow.

    Roundabouts are relics of the pre electric stop light horse and buggy days… but that will likely be a great match to the once paved, now gravel roads that are growing across the county.

  8. springa73 says

    OverlappingMagisteria @#4

    Yup, rotaries are common here in New England. It wasn’t until I was in my 20s that I realized they had other names in other (English-speaking) places.

    As for whether they are better or worse than other types of intersections, I would say that they are actually smoother than other types if the drivers are all familiar with them. If a significant percentage of drivers aren’t familiar with them, they are a lot worse. I grew up learning to drive on them, but for someone who has never driven one before and has literally seconds to learn, I’ve heard it can be quite scary and dangerous.

  9. Jenora Feuer says

    There are multiple roundabouts near the airport in Victoria, B.C., and PDF maps indicating which sequence of turns you want to use to go from one location to another:

    Apparently there actually used to be a roundabout in downtown Victoria, back in the 1960s:

  10. sonofrojblake says


    essentially blocked the flow of traffic on one of the roads because there was never a break in traffic in the circle

    What often causes that is the following. Imagine a road A-A’, onto which butts a side road B -- a T junction. Traffic flows from A to A’ uninterrupted (the city is a A’, a large suburb at A and a rural hamlet at B).
    Wanna get A-A’? Great. Vice versa? Great. B to A? No problem -- you don’t cross the flow of traffic in that direction and a gap is usually likely. It’s MUCH harder to cross the flow to get from B to A’. Not that many people do -- the hamlet at B is small so traffic is light.

    So the planners put in a roundabout. People going A-A’ or vice versa barely notice. People coming from B get to pull out across the flow of traffic, super. Everybody’s happy.

    Then the planners give permission for another 5,000 houses at B. Suddenly the place is full of commuters coming from B to A’, and nobody from A can get onto the roundabout, causing huge queues.

    This exact scenario has played out in at least ten locations within an hour’s walk of my house.

    The solution motorists have found is that the responsible ones actually allow people who do NOT have right of way onto the roundabout. In an ideal world, when there’s a queue at two entries, traffic from both “zips”, each car with right of way allowing just one car without it into the queue. It’s a joy to see, spoiled only by the predictable selfish or oblivious asshole usually driving a BMW who is so important or in a hurry that they HAVE to gain that extra four metres by NOT letting you in. In general though, zipping onto a roundabout is a mildly pleasant experience that reminds you that most people are actually OK.

  11. blarg says

    You are taking heart over a situation that only works when people do NOT follow the proper rules of yielding? And the person who does follow the rules is an asshole? That cannot be a sustainable system. I see the driver behind your Good Samaritan, not realizing the special rules for this particular intersection, rear ending the nice rule breaker when they unpredictably slow to let someone in. Or even worse, the forth person behind bearing the brunt of it when traffic suddenly accordions.

    This reminds be or people slowing, sometimes almost stopping, on a state route or highway to let someone in from an on ramp despite the fact they have the right of way and are traveling much faster, bringing both paths dangerously to a halt. The unnecessary and inappropriate yielding creates hazards for both lanes. At least in that situation with a more traditional merging system there are places for others to maneuver (side berms, medians,…) unlike roundabouts, which, around here have no optional egress for accident avoidance.

  12. sonofrojblake says

    OK, two things. First, read what I wrote. Specifically:
    when there’s a queue at two entries, traffic from both “zips”, each car with right of way allowing just one car without it into the queue”

    What I wrote is predicated on the idea there are TWO QUEUES, which I observe is very common.

    So now we come to your fantasy:

    I see the driver behind your Good Samaritan, not realizing the special rules for this particular intersection, rear ending the nice rule breaker when they unpredictably slow to let someone in

    If you rear ended the car in front, you are:
    (a) driving too fast
    (b) driving too close
    (c) not paying attention
    (d) all of the above.

    There’s just not any excuse for driving into the car in front. If they “unpredictably slow down”, simply brake. Not got space? YOUR FAULT. Own it. And if you’re in a queue, i.e. doing only walking pace at best anyway, then making sure you’re only six inches from the car in front so people joining the flow can’t get in is just antisocial. So yes… assholes for sticking to the rules, absolutely.

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