Roundabout Thoughts

Another cyclist has died negotiating Bow Roundabout whilst using an East London bicycle "superhighway".   Bow Roundabout is the junction of the A11 and A12.   Surprisingly it is only a two lane roundabout, but it does also feature a cycling facility.   Looking on Google Streetview this was the usual, lethal cycle lane around the outside, but I don't know how it has been modified for the "superhighway" other than what you can see here, where you will notice that the death count appears to have risen since the BBC article.

On this forum recently the death of a cyclist on Dartmouth Circus was announced.   Roundabouts are lethal for cyclists, but they don't have to be.   In Germany this summer I noticed that all the roundabouts I encountered were of a different design to those in Britain.   For some reason I just cannot imagine it took me an age to find a photo of this type of roundabout, but thankfully contributor to Wikipedia Niteshifthas photographed one of them:

Note the cobbled section in the middle.   I don't know for certain why this is done, but I know why Germans place similar cobbled sections down the centre of roads in towns.   The idea is that you can drive across the cobbles if necessary, but it will be a rough ride so you have to take it slowly.   This discourages overtaking moving vehicles.   I think the idea behind the semi-cobbled roundabout is to narrow the smooth section to one lane to prevent drivers using the roundabout as a small dual carriageway, whilst allowing drivers of large vehicles to negotiate the roundabout without dragging their rear wheels through the shrubbery.   The cobbled section also allows the roundabout to continue to function if one exit starts backing up.   Since the roundabout has only one lane (and only one lane on the entrance to match), such roundabouts are much easier for cyclists to negotiate.   As the traffic slows on the approach you can take your opportunity to move to the centre of the lane, and stay in the centre for the entire duration of your passage through the roundabout.   Since there's only one lane no hair-raising lane changes are required, and the dangerous concept of riding around the outside is irrelevant.   Also, anyone who tries to use the cobbled section to barge past you will find the experience unpleasant.

Such roundabouts are of course much easier for motorists too.   Coming from a right-hand drive country, I was hugely relieved that all the left-hand drive roundabouts I encountered were of this design.   They were in fact easier and less stressful than T junctions.

A single lane roundabout like this has a greater capacity than you might think, because it's easier than on multi-lane roundabouts to eyeball other road users and to take your turn.   However, what happens if one lane just isn't enough?   Well again there's a solution, and this time it's a solution I've encountered in Britain.   It's called a spiral roundabout.   They're pretty rare in my experience, but their operation is quite magical.   Since they are quite rare I'll risk teaching the sucking of eggs and describe their operation.   You pick the correct lane lane on the approach, and stay in it.   The lane markings spiral outwards on the roundabout, so they will guide you to your exit:

You can pass through the largest, busiest of roundabouts without a single lane change except for the initial lane selection.   However, if you realise in time you picked the wrong lane, traffic permitting it's possible to switch to the correct lane on the roundabout in the conventional manner.   Details on spiral roundabout lane markings may be found here in Figure 3/4 on Page 3/5.

Now imagine such a roundabout with traffic lights and an advanced stop line on the entrance.   Even if the roundabout was very busy, you could wait on the left for the red light, pootle across in the advanced stop zone to the centre of the correct lane, and when the lights turn green pedal off staying in the centre of the lane until the roundabout markings guide you off at your exit.   It would be pretty grim, but I reckon it would be doable, unlike attempting the same on, for example, a three lane conventional roundabout.   Why aren't spiral roundabouts more common?   I've no idea.   Maybe someone can tell me.   Would I prefer something off-road?   Absolutely (so long as it wasn't hopelessly slow).   Alas off road probably means "too expensive".