Where is it?
Halfway around the A720 Edinburgh City Bypass, where two of the city's radials cross the bypass and each other.
It was nominated by Chris Williams.
What's wrong with it?
Imagine, if you will, the city of Edinburgh. Around its southern fringe lies the A720, otherwise known as the City Bypass, a grade-separated dual carriageway (complete with hard shoulders and motorway-like restrictions) that speeds traffic around the urban area. It's like some kind of dream.
However, largely thanks to this junction, if the A720 is any kind of dream, it's the sort that makes you wake up screaming at three in the morning. It's pretty obvious from the diagram what's wrong with it — it's a roundabout. Traffic chaos day and night is caused by the fact that this junction, in the middle of what is effectively a motorway, is one flyover short of adequacy.
Naturally, traffic engineers have done their best to entertain those stuck in the congestion this roundabout causes by surrounding it with cheery red, amber and green disco lights.
Why is it wrong?
There are two schools of thought on this one, and each is equally plausible. The first is the more optimistic; when the Bypass was designed and built it was thought that the volume of traffic entering or exiting the road here would be a significant proportion (ie, the flows of traffic between the two arms of the A720 would not be heavy enough to warrant grade separation). With the benefit of hindsight (and all the thinking time that a typical Sherriffhall traffic jam permits), it's clear as day that this idea was wrong.
The other, more frightening, answer is that the junction is built on the site of old mine workings, and that this made grade separation impossible. The ground is not stable enough to support a flyover. This is backed up by the fact that the design of the junction does not even leave room for future grade separation. If this reason is true, then the future looks grim for regular users of this junction.
What would be better?
A flyover and a free-flowing A720. Or an underpass. Anything. Please. Quickly.
Right to reply
3 options now being considered by Transport Scotland. 2 dumbbell layouts and a grade separated roundabout. Details on Transport Scotland website.