Where is it?
North-east of Exeter, a major interchange is formed where long-distance traffic on the A30 ends its long journey from Hampshire and joins the M5.
It was nominated by Tobye Smith.
What's wrong with it?
A valiant attempt to connect the M5 to the A30 with free-flowing links, brought low by the twin scourges of local access roads and traffic lights.
The tragedy can only be truly appreciated when you realise that this was originally meant to be a free-flowing junction, and when it was first built it was, but at that time the A30 was a single carriageway road almost all the way to Basingstoke. When the expressway was built between Honiton and Exeter, and the A30 became a fast dual carriageway right up to this point, traffic lights were added, breaking the free-flow links.
Why is it wrong?
Things change. This bit of the M5 opened in 1975, at which time the requirement was for a junction where trunk roads met: the A30 was expected to be improved to form a dual carriageway across the South West, and its traffic was expected to merge with the M5 to get around Exeter. The original junction had a loop to carry traffic from the northbound M5 to the eastbound A30, and a simple sliproad from the A30 back to the M5 southbound. It was even laid out to allow two more slips, linking the southbound M5 to the eastbound A30 and the westbound A30 to the M5 northbound.
When the dual carriageway finally arrived the requirement had changed. Now access was needed quickly and cheaply from the adjacent part of Exeter to the M5, so the missing sliproads were built in a different configuration to that originally planned, and traffic lights were introduced so that traffic in all directions could use them.
The final indignity arrived around 2013 when a new direct access was built from this junction to the developing area around Exeter Airport, which had previously been reached via another junction on the A30, meaning that the whole complex now needed more traffic lights, filter lanes, cut-throughs and complications.
With the current plan being to complete the A30/A303 route by dualling the A358, to reach the M5 further north near Taunton, the future for this interchange is to be a local junction for Honiton and the north end of Exeter — and not for trunk road traffic bound for London at all.
Of course, the people who designed this junction in 1975 couldn't have known that there would be enormous commercial developments and an airport here that would want access to the A30 and M5. They also didn't seem to think anyone in the northern part of Exeter would ever want to reach the M5 at all, which is a lapse that's slightly more difficult to explain.
What would be better?
These changes of plan are all very well, but the fact is that this junction is, today, used by an awful lot of traffic doing exactly what the designers envisaged back in 1975 — getting between the A30 and M5 as part of a long distance journey — and even if the A358 is dualled to Taunton, a significant number of them will continue to do so. All that traffic now gets caught up in the traffic lights intended for people getting to the supermarket and the office park near the airport.
The A30 towards Honiton is an excellent road, virtually a motorway, and deserves a better connection to the M5. Let's leave these tangled sliproads as a local junction and build a new pair from the A30 to the M5 to the south, bypassing all of this and relieving it of a great deal of traffic that doesn't want to be here anyway.
The alternative, which would work just as well, would be to demolish the business park, the airport and the northern parts of Exeter, and then return this junction to its original form. That might be a bit more expensive, though.
Right to reply
This junction upsets me. Please make it stop.
For some reason or another I seem to find myself in Exeter two or three times a year and in some varying form, traversing this mess.
For a number of years it seemed to be in a permanent state of construction. But now it's finished it's hopeless.
The problem starts with the local access road to Blackhorse village. Why is it still there? And why is it so over-provided for. God only knows why the powers that be didn't just close it off completely and divert the traffic (as you say) to the proper airport exit a mile or so to the East on the A30 - where there's ample room to expand the slip roads should they so desire. For extra banter they've added a bus lane running straight through the middle as if there wasn't enough traffic conflicts already.
The junction seems to ignore the fact that people might actually want to carry on into Exeter itself, and rather spoils a nice stretch of express A30 with all those traffic lights.
I'm not entirely convinced semi-regular long distance users will be conned into the longer 358 de-tour to the north...and miss out on that rather splendid bit of A30.
What really needs to happen is that the junction should be partially by-passed to the south so A30 route traffic can be grade separated properly onto the M5. Traffic entering Exeter on the M5 from the south doesn't really need to be here, force those off at junction 30 and you can do away with a slip. Get rid of the meddling local road and finish off what's left (which will just be north facing slips for the M5) with a modest roundabout.
As much as people dislike this junction, I'm quite a fan of the 2013 improvements - it's nice to finally be able to get out of Exeter onto the M5 South without having to muck around through Sowton rush-hour traffic jams for 30-45 minutes to J30.
I think you hit the nail on the head with building a new junction for A30 long-distance traffic and keeping this one otherwise unchanged for local traffic.
The two qualms I have though is, firstly the lane arrangement eastbound since the 2013 works, where an extra lane appears on the left and then disappears from the right, shifting everyone over for no reason when they could have just painted the lines diagonally, and secondly the northbound on-slip, which I had to use for the first time yesterday (and many a time in the past have been wary of when passing it on the main carriageway) - it is far too short, it feels no longer than a non-junction Services exit!
The worst part of this junction is going from the northbound M5 to the eastbound A30.
The right-angle turn is sharper than it looks and the road markings are virtually obliterated. Cars on the outside can cut the corner and those on the inside can run wide.
You are therefore trying to watch both sides of the car at the same time and trying to keep in your own lane.
To make things more interesting there is always the chance of stationary traffic just ahead when there is a tailback from the traffic lights just around the corner.
The reason junction 29 has been hacked about so badly is certainly partly to do with the massive explosion of development around it. But I think it also has a lot to do with the poor design of junction 30 (Sandy Gate). When I first moved to Exeter in '97 you had to use junction 30 to get in and out of the city, and it coped, but only just. Queues worsened over the years, and adding extra slips to 29 took some of the pressure off.
The strange thing is that the carriageways of the A379 spur between Sandy Gate and the ring road flair as though there was meant to be a pair of free-flowing slips linking it with the motorway (see also junction 21 at Weston), though I don't know for sure if that was ever seriously planned and if they would have pointed north or south. North would certainly have caused merge hell given how close together the two junctions are but south would have meant pretty sharp curves, not to mention dealing with the massive hill in the way, where the rugby ground is now.
I'm surprised no one has mentioned the ludicrously short merge onto the northbound M5, though. It's downright dangerous if you're not fully prepared or you're following someone slow. I had to borrow a bit of hard shoulder there the other day to avoid sideswiping someone, which was hair-raising.
Some of the issues arise because of the Sandygate slips to and from the services adding greatly to the traffic on the Sandygate roundabout which is afflicted by ill-marked lane changes and traffic lights. Junction 29 and 30 both cause confusion. Accidents are frequently caused by drivers careering from the southbound slip at J29 straight across red lights at the junction with the A30.
The lane changes on the East bound A30 cause safety issues similar to the first bend on an F1 circuit.
Westbound last-minute traffic joining the M5 at J29 leads to many sudden and late pushing into the slip. That slip is two lanes but soon reduces to one.
All in all a shockingly bad and inherently unsafe junction design.