As simple as possible, as complex as necessary

The simplicity of roundabouts

1 July 2011

The best applications of simplicity often go unnoticed. In the UK, roundabouts are a common and long established feature of our road network, but reading a BBC piece on how British roundabouts appear to be gaining popularity in the US reminded me just how simple and effective they are as a way of managing intersections.

Couple a simple circular layout with a single rule - give way to cars already on the roundabout - and you effectively have a junction that manages itself.

Contrasted with traffic light systems, the benefits are numerous:

  • Cheaper to build;
  • Cheaper to maintain;
  • No risk of electronic failures of or damage to control systems;
  • More fuel efficient, since stopping and starting is greatly reduced;
  • Less polluting, since engine idling is greatly reduced;
  • Journey times are shortened: in the BBC video one driver claims he can save 15 minutes on his commute by choosing a route with roundabouts as opposed to traffic lights;
  • Statistically fewer accidents;
  • Visually more attractive: roundabouts afford great opportunities for floral, artistic or other aesthetically pleasing displays;

The main downside is one that often dogs convention-based simplicity: unfamiliarity. If you don't know about or are not used to that single give-way rule, you may find them intimidating.

Roundabouts from hell

The rule is key though. Without it roundabouts can make matters worse. I will never forget the first time I was driven around the Arc de Triomphe in Paris twenty years ago. The French highway code at the time had a blanket rule of "always give way to the right". Everywhere. Including on roundabouts (which unlike in the UK run anti-clockwise of course). So even though you were on the roundabout, you had to keep stopping for any car wanting to join it (since they would be feeding in from the right). Completely potty. My companion at the wheel agreed and said UK style roundabouts were starting to be introduced. Perhaps today they are the norm.

Magic roundabout

Google map of Swindon's 'Magic Roundabout
The Magic Roundabout: scary-looking but actually quite safe

If our US friends do also follow suit in adopting roundabouts widely, then I would advise them to try and avoid having too many in close proximity.

In the town of Swindon, 80 miles to the west of London, there is an egregious example of how a simple solution applied thoughtlessly can lead to a mess of complexity: the notorious Magic roundabout.

Although regularly featuring in lists of the worst examples of road design, it apparently has an excellent safety record because the traffic moves around it so cautiously.


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