A9 - M90 - A93
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Ordnance Survey map - Alternative aerial view
Where is it?
The end of the M90 spur (originally the mainline M90) at Perth, where it meets the A9 and the A93 into Perth itself. From the map, it might not look much, but it's one of the busiest roundabouts in Scotland and the centre of the country's road network.
It was nominated by 'Mad Manx'.
What's wrong with it?
Bad Junctions is about poor design, not just places that have run out of capacity. That's why most flat roundabout junctions that have problems don't make it in. Broxden is something quite different.
For one thing, it doesn't seem to be a very well designed roundabout. It's on a steep slope, meaning that heavy goods vehicles tip over here with alarming regularity, causing frequent hold-ups to two of Scotland's key trunk routes. It is statistically the most dangerous roundabout in Scotland because of this.
There's also the small consideration that there is simply no way around it. You can't avoid it, except possibly by going through Perth itself, which is hardly recommended. But there are no easy routes to bypass it in any direction. This is unhelpful when Broxden is the collision point of north-south and east-west journeys across Scotland, and one of the calling points on most journeys between places like Glasgow and Aberdeen or Edinburgh and Inverness.
Why is it wrong?
British road planners (and their whip-cracking political leaders, who write the rule books) like roundabouts. Roundabouts are cheap, they require no maintenance like traffic signals or bridges, they are easy for drivers to use, and they are almost unbelievably versatile. You can take any bizarre road layout and hammer it into a sensible shape with a couple of roundabouts.
It's great to have such a useful tool in your armoury. The problem is that the roundabout is also the default choice when the traffic flows and turning movements aren't very decisive or you can't make your mind up about who should get priority through the junction. That is what seems to have happened here. You can almost imagine the conversation...
"We've got three high-speed roads meeting here west of Perth. Should we free-flow them together somehow?"
"Which one is the main road?"
"Er... we don't know. It looks like people will be moving around a lot so there won't be a dominant flow through it."
"Oh, that's fine then. Just stick a roundabout in and we'll put the spare cash towards the Christmas party."
What would be better?
Without having access to the traffic flows and a model of the turning movements that are made here, it's hard to say where a flyover or a bypass should go. Do more people go between the A9 to the north and the other arm of the A9, or do most of them actually head for the M90? Without knowing it's hopeless to speculate.
Some quick and effective fixes could be found, however, by some more left-turn lanes to enable, say, northbound A9 traffic to continue non-stop. You could also erect some signs warning lorry drivers that there is a severe risk of tipping over, because the word obviously isn't getting out. Just an idea.
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