Where is it?
North-west of Oxford, the A34 is running north-south as a bypass of the city, the A40 is running east-west as a bypass of the city (more or less), and the A44 is a major road out of the city passing through on its way to the countryside. The city's outer ring road uses bits of A34 and A40, and has to get between the two.
It was spotted by Martin Smith.
What's wrong with it?
This junction appears to have been designed by several different committees, each working on their own discrete area, and which were not talking to each other due to some fundamental and long-running dispute over how the interchange ought to be laid out.
The result is a big tangle of roads that only really interact with each other in the most disinterested and careless ways, making journeys from one to the other unnecessarily tedious and disorienting. Oxford City Council have made a contribution by placing a park and ride site on the junction, accessed by a further set of traffic lights that delay traffic travelling between the A34 and A40. Thanks, guys.
Why is it wrong?
As you might be able to tell by the series of roundabouts that appear to be used in place of any really good ideas for how to connect multiple roads together, this junction really was built in several stages by different groups of people who hadn't consulted with each other. It is complicated by the A34 running on a lengthy viaduct over the top of the A40, making any interchange there difficult.
It is, of course, one of those places where the design of a simple, effective junction is nearly impossible anyway because of the many conflicting routes that pass through here and the nature of the people who live near to it.
The situation hasn't been helped by some particularly inept planning decisions in the time that has elapsed since then, of course: the location of Peartree Services and the park and ride site seem to have been wilfully chosen to cause as much disruption as possible, and the laughable size of the southernmost roundabout can only be some sort of in-joke amongst whichever set of traffic engineers set it up.
What would be better?
One finds oneself hoping that some sort of extremely localised natural disaster might strike here and clear away the mess — perhaps a tidal wave down the Oxford Canal that would wash the A34 viaduct away, or a very small volcano that would rise up in the triangle of land between the roads and cover them all in molten lava without doing any damage to the nearby housing estates.
There are wider problems to be fixed here, you see. The A40 northern bypass runs through the suburbs of Oxford, when what is really required is a fast dual carriageway to link the existing Witney Bypass to the Oxford Eastern Bypass. You could connect that to the A34 at a suitable high-capacity junction, and make a local access point to reach Oxford, the A44 and other assorted local amenities off that.
Whoops, mind your head — those pigs are flying a bit low today!
Right to reply
Locally this is thought of as three junctions - Loop Farm roundabout (A44 and A4260 to Kidlington, most of the latter being a part of the Oxford western by-pass severed by the Gosford diversion opened in 1990); Pear Tree Interchange (A34 and A44, converted from roundabout as part of the Gosford diversion) and the Wolvercote roundabout (A40, A44 and [unsigned] A4144 from Oxford; built in 1930s as part of Oxford northern by-pass and little changed since).
I'm sure Pear Tree interchange was left as it was because it was assumed that the so-called 'Tin Hat' scheme which would have built a new dual carriageway to by-pass the suburban stretch of the Oxford northern by-pass would follow swiftly in the 1990s. Needless to say, it didn't happen and probably never will. There have been schemes for relief roads, including one from a new roundabout to be built at the park and ride junction down to the A40 running parallel to the A34 at ground level, but this is tied in to proposed industrial development in this triangle to pay for it, and there is huge local opposition - not only because it's green belt, but because new industry will only generate more road traffic.
I've never personally had a problem with this junction. Well, to be more precise, I have had issues here but they're to do with the massively congested M40 junction 9 a bit further north.
You wrote "This junction appears to have been designed by several different committees, each working on their own discrete area". Well that's not really surprising given the junction layout as a whole dates from three separate schemes each spaced about 30 years apart from each other! The A44 is centuries old (it has, in order, been part of the A42, A34 and A43 - is this a record?). The A40 here opened in 1935, the A34 in 1964, and the flyover at the top in 1991.
What your map also doesn't show is that where the A34 crosses over the A40 is right next to the main line railway immediately before the branch to Birmingham splits from the branch to Worcester, and it's also right on the flood plain of the Thames (or the Isis if you're feeling posh). There physically isn't the room to even put an at grade roundabout here without doing some serious and expensive faffing about. Be grateful the two roads didn't just slam into each other at a pair of lights - something that could well have happened if the western bypass had been built in 1934 instead of 1964!
Also, it should be noted that there isn't much A34 to A40 traffic if you look at the wider picture. A34 north to A40 east has either taken the other flank of the ring road along the A4142, or further back has taken the M4 and A404. A34 north to A40 west only really serves the Abingdon / Witney area, more long distance traffic takes the M4 and A419 / A417 to Gloucester. The dominant traffic flow here by miles is the A34 queuing up to the M40 - which is Southampton - Midlands traffic.
Honestly, if you want a real bad junction, come down to Canterbury where the A2 meets the A28 - it's restricted access (like all A2 exits into Canterbury), so A28 NB to A2 WB requires going through the city centre. D'oh!
I've only used this junction twice, and hope I never have to again. It is an overloaded, badly thought out mess. During my second time queueing from the A40 to the west to turn up towards the A44/A34 I saw many of those "in the know" cut through the BP petrol station to do the same movement. It's a dog's breakfast but as has been said it's unclear what can be done.
My other half uses the A40 from Glos to Oxford (and beyond to Milton Keynes via A34) on a regular basis and talks of it taking the best part of an hour from the end of the Witney by-pass to the Wolvercote roundabout. Clearly, Mr Swann does not use this regularly!
The A34 is not on a long viaduct as this author claims. You only have to drive under the A34 along the A40 to see this. Much of it is on an embankment (you can see it on Google Streetview). What would be most helpful are two lanes alongside the A44 from the Pear-Tree to the A40. Not impossible and anywhere else that would see this level of congestion on a daily basis would have seen some kind of alleviation many years ago.
There's always work going on along this stretch of the A40 - sadly none of it ever seems to be about improving the road itself in terms of relieving congestion.
Had to come this way a couple of times last year en-route between Crewe and Bournemouth so I was actually driving through on the A34. The traffic is always horrendous on this part of the Oxford Bypass, and although one usually keeps moving it is an icon of the failure of our transport planners and builders to address demand and sort out the bottlenecks all over our green and pleasant land. If you get too stressed up, try going along the old road for a bit north or south between M40 and this junction - now a B road and virtually empty, it gives the driver a little rest before "bashing on". If you're feeling sorry for youself, just look at what the poor inhabitants of Botley have to live with - a virtual 2-lane motorway through their midst !!
I have been using this junction for upwards of thirty years before there was an A34 fly-over or the M40 was built.The problems have grown with the traffic use. Like many others (see my other posts) slapping another layer on it or another local 'upgrade' has just made things worse. The up-grade of the A43 (greatly needed) although not actually part of the junction has fed in more traffic. It's all caused by Icelandic butterflys flapping their wings.