Sunday, 2 December 2012

Britannia Roundabout

At frequent and fairly irritating intervals, the subject of Britannia Roundabout comes up in the local news. It is always the same story. It's a terrible place to drive, nobody knows how to use it and, most recently, it was the source of the most crashes in 2011 - over and above all other city intersections.

Various solutions have been suggested over time. They include a $100m underpass, putting in traffic lights or turning the whole thing into a signalised intersection.

I do not doubt, as some commentators suggest, that some of the crashes are caused by drivers not really knowing how to use a roundabout but I think that the biggest problem with Brittania Roundabout is that it is not really a roundabout.

Here's a view of it from above:

Most roundabouts are round - hence the name. This thing looks like an Aids ribbon rotated to the right:

Where the two ends of the ribbon cross is probably the worst bit of the roundabout.

In the top left of the picture, a white truck is approaching the roundabout where it has to give way. The driver has to watch for traffic coming from her right (left of the picture just above the bright green car partially hidden by the trees). But the driver also has to worry about traffic travelling diagonally from the bottom of the picture to the top left. That traffic either travels straight to the top left of the picture or it may turn right and follow the roundabout in front of the truck.

So the driver is worrying about traffic from two directions about 160 degrees apart. And with the traffic coming towards her it is generally not until the very last second that it indicates right and follows the curve of the roundabout.

Those drivers coming from the left (just above the bright green car) also have to worry about traffic travelling to the top left of the picture - and there is generally a lot of it. Some travels straight on, some goes around the roundabout.

The picture in the news story illustrates the conflict that the ribbon design creates:

Source: The Advertiser

So what do we do? I think the most obvious solution might be to turn Britannia Roundabout into a roundabout.

One option that can increase the capacity of the roundabout is to install a 'turbo roundabout'. It can be done either with or without traffic lights. The idea behind it is that drivers are forced before reaching the roundabout to choose the exit they require. They do that by selecting the correct lane for that exit before entering the roundabout. It prevents lane changes and conflicts on the roundabout itself.

Above all though, it needs to be turned into a proper roundabout to get rid of that terrible source of conflict on one side.

The underpass idea is not a bad one but it needs one tiny change. This is a view from Google Earth of a roundabout in Harderwijk in the Netherlands:

David Hembrow has discussed it and others in detail. Note the red paths separate from the grey bitumen of the roads. They are the cycle paths. Not once is a cyclist forced into a pinch point as they are generally on Australian roundabouts. And nowhere are they required to cycle anywhere near a heavy goods vehicle.

We have paths through the parklands on that side of town. This is how you connect them with the eastern suburbs.

Here's the roundabout from the cyclist's point of view:

Imagine seeing Britannia Roundabout like that.


I cannot of course take any credit at all for this but this has been fixed. Instead of one, there are now two roundabouts:

Whenever I use it, it works so much better. Traffic is still slow in rush hour but my limited experience is that the tail-backs are not as long as they used to be.

It is a big improvement if you are in a car but on a bike? I wouldn't know because I have never gone near it on a bike and I do not intend to. Ever. Very occasionally, I see someone on a bike daring it and I wince in sympathy. Check out the video above. That's the only way to fix it.


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  2. Britannia Roundabout - Ukrainian holiday.

    Interesting segue.

  3. Welcome to Britannia Roundabout. Our prime example of civilisation going backwards