There is a story that has travelled incredible distances and, perhaps more than anything else, given the unassuming Wiltshire town of Swindon cause to be discussed across the world. It's not a famous person or a particular achievement. In fact, it's far more mundane than that: it's a roundabout.
The Magic Roundabout is a fabled, almost mythical entity discussed in hushed tones by American road enthusiasts already wary of Britain's many fast, multi-lane roundabouts. Stories of it are swapped with fear and trepidation among those planning a trip to Swindon. Guide books that would otherwise have no reason to mention the place find room for a paragraph or two when this little junction is concerned.
Why? Well, because it's the roundabout that goes the wrong way, of course!
What is it?
In Swindon town centre, just next to the local football stadium, is a junction where five roads meet. Until the 1960s it was a standard roundabout - the usual British way of dealing with unusual multi-directional junctions - but even then it had traffic problems.
The most important element is, of course, that it works both ways. Because traffic can choose the shortest path between its entry and exit points, it spends less time on the junction. One of the most common movements - from Fleming Way to Queens Drive - now involves travelling about half the distance as it did when this was a conventional roundabout. And if traffic can get out more quickly, that adds up to fewer vehicles clogging up the junction at any one time.
The trade-off is that there are now a much greater number of points of conflict - places where one stream of traffic crosses another. This effect is offset by a simple priority rule on every approach to every mini-roundabout, which means that no vehicle should be held up for very long at any "give way" line. Additionally, every approach has space for several vehicles (usually three but sometimes more) to wait alongside one another: that way, when there is a gap and it's safe to move off, several vehicles can all go at the same time.
It looks like utter mayhem from the sidelines, but it's actually incredibly controlled. Traffic keeps moving almost all the time, waiting only a few seconds to join each mini-roundabout and thus steadily travelling at low speed across the junction. A normal roundabout would involve long waits to join; signals would involve bursts of movement and long enforced stoppages. As a result, it has been calculated that the Magic Roundabout has a greater throughput of traffic than anything else that it would be possible to install in the same space. Magic indeed!
How was it created?
The first Ring Junction was installed to replace an existing large roundabout in Colchester and, like the four-way design above, had a square central island. Traffic turning left or going straight ahead went around the outside as usual, and "wrong way" circulation could only be used to turn right. Really it was still a big roundabout with gaps in the central island; the RRL called them "unhooked" right turns. Unfortunately, its accident record was terrible: it proved much more dangerous than the congested roundabout it replaced, and after fiddling with road markings and signage, the experiment was abandoned, with the junction returning to its previous state.
There's a "magic roundabout" by Hatton Cross tube station in London (just inside the Southern perimeter of Heathrow Airport), and it works very well indeed. In spite of it being a major artery into the airport and having a very busy bus station adjacent to it, I've never seen it congested or clogged up (and I used it almost daily for about 15 years before moving out of the area).
Couldn't leave the intersection for 15 years? ))
Thank you for this post and the whole website - I have long been fascinated in Colchester's magic roundabouts & came here (as a member of the SABRE forum) as I saw a reference to this.
On this occasion I am prompted by comments and photographs in a Colchester reminiscence Facebook group - I am interested to read more about the development of the Colchester scheme.
Having been a long-term (50 years) road-geek and long-term lurker then member of Sabre, I became aware of Swindon's Magic Roundabout around 20 years ago and was intrigued by it. Still being at that time a fan of roundabout junctions (less so now that I live in Australia, and having seen how well traffic signals can work and how badly UK roundabouts perform under stress) I longed to visit. I finally did that around 2012, and was fascinated and impressed to see it in action. I parked up to observe the traffic for a while before trying it out myself, and was then pleasantly surprised to find that it was not too daunting by about the third pass! (I imagine a newcomer though, with no advance warning, would be horrified and freeze for a while at the first give-way line). Still, much as I admire the daring to proceed with it, I simply cannot believe that it can pass more (peak) traffic than a modern well-designed signalised intersection occupying the same footprint. Incidentally, if I were to be the designer, I would probably stop-up one of the 5 roads to simplify matters.
hi i am 58 i have lived in west bromwich b70 all my life and at the end of shaftbury road b70 we to have an island where you drive round it in either direction its been like that ever since it was there
I think these are a good idea, but do have some issues. The main one being that, when busy, there is always the "lane change" conflict that comes about. That is, for example, when doing, say, right, right, left at a sequence of three minis, there will be other vehicles that have entered at no2 and want to exit no3 to the right. So, obviously, major vigilance is required and it works, but risks are higher that others are not so careful!
Peter Freeman You say ‘I simply cannot believe that [the Magic Roundabout] can pass more (peak) traffic than a modern well-designed signalised intersection occupying the same footprint’. Do you have any evidence for this belief?
In the article it says that, in the course of the development of the mini-roundabout in the 1970s, ‘one RRL researcher, Frank Blackmore...[noted] that the design was also superior to signalised junctions, following a Peterborough experiment where an extra 1,000 vehicles could be handled every hour by a new small roundabout at a previously signalised T-junction’. The article also notes that the Swindon Magic Roundabout ‘is one of the few places where the jams have never really returned despite forty years of traffic growth’.
I’m prepared to be persuaded that a ‘modern well-designed signalised intersection’ could pass more peak traffic, but I would like to see the evidence.
Magic Roundabouts work where there are multiple - 5+ routes to deal with. To bring all those together requires contorted signal timings, significant times lost intra-green and, unless you're going to make it a barrier to pedestrians, more time lost allowing a complete pedestrian phase rather than requiring pedestrians to cross every road in stages.
Traffic lights are also more crude - they have some idea of traffic, but not to the same degree as a driver. Both at Swindon and Hemel Hempstead before you need to commit to lanes you are given a view across the junction so you can travel a longer way around if there is congestion on one side. This is especially important at both junctions because the joining roads all have different capacities and non-linear demand. A MR automatically optimises itself for changes in demand. Football stadium kicking out? Football fans can travel both ways round the roundabout for the hour or so needed. Much more civilised than around here where people turn the "wrong way" onto less busy roads to avoid the queue, then do abrupt u-turns.
There's also just the driver factor. With astute driving you rarely need to stop on a Magic Roundabout. As Chris says, once you actually try one they're intuitive. Each mini-roundabout only has three entrances, so you only need to decide if you are going left or right and get in the appropriate lane. Because at the previous roundabout the driver alongside you will have chosen the other option, changing lanes is not a problem because they will have left the roundabout.
As long as you know what exit you are taking (which is ordinarily only every first, second or third) and treat it as a simple task of getting in the left or right lane at each roundabout, then it's very easy.
There are a couple of flies in the ointment, such as when they close of exits as at Hemel but hey, it still chugs along alright :)