Where is it?
North of Bristol, the point where two of the most important roads in South West England cross each other and, rather ambitiously, attempt to interact with the local road network at the same time. This is actually two junctions on the M5 that are stuck together — junction 15 for the M4 and junction 16 for the A38 at Filton.
It is one of the most-nominated Bad Junctions ever.
What's wrong with it?
In its component parts, nothing at all. It took me years to work up the courage to actually list this on the site because junction 15, the M4-M5 interchange, is a four level stack, one of the highest capacity junctions it is possible to build and one of only three of its type in the UK. We could do with far more of them, so it feels quite wrong to see it here.
The Maltese Cross at Almondsbury isn't the problem (though the motorways it connects could do with a bit of extra capacity). The trouble is that it has been glued on to another hapless junction with the A38, a major road into Bristol and now surrounded by shops, offices and car parks.
Linking the two overloaded junctions is a collector-distributor road setup that collects traffic for a brief scramble to change lanes before splitting up into sliproads for the next junction.
Why is it wrong?
In 1966, the year it opened, Almondsbury was the most incredibly complex and exciting junction the UK's road network had ever seen. It had a free-flowing interchange with four levels! It had four motorway carriageways running parallel to each other! It had it all.
Unfortunately what happened to Almondsbury is traffic. When there's not many people on the roads, all that lane changing on the outer linking carriageways is easy. Once it starts to get busy you have problems: traffic coming from the M4 westbound has to move right and right again on its way to the M5 southbound, while trying not to bang in to the M5 southbound traffic frantically moving left to reach the A38. The more vehicles there are, the harder it is to maneouvre, and the more everyone is in everyone else's lane.
The worst bit is that all of the roads here are predisposed to come to a shuddering halt in the summer when the holiday traffic is passing through, and any sort of traffic jam blocking those collector-distributor lanes will then spread onto all the surrounding sliproads and make the perilous lane-changing moves even more dangerous than before. Changing from a lane travelling at speed into a stationary one is not an easy trick to pull off.
What would be better?
This interchange is crying out for some investment. It was once the marvel of the motorway network and it doesn't deserve its bad reputation. I feel quite sorry for it.
The most obvious improvement is to get rid of those outer collector-distributor carriageways, and replace them with a braided junction. Separate sliproads would cross each other with flyovers to carry conflicting traffic movements without incident.
Right to reply
What isn't mentioned in the article is that, next year, the M5 is getting Active Traffic Management. Whilst all sources state J17 to J15 (Cribbs Causeway to the M4), I can't see how it is physically possible to have ATM around here. This may cause complete and utter chaos, which could potentially kill off ATM for good.
And whilst the M5 has the 'summer Saturday' reputation, it is getting to the stage where the Bristol section is gridlocked all year round. The tourists start at Easter, and don't stop until September. Cue the inevitable annual roadworks on the Avonmouth Bridge, which almost always cause queues back to at least Almondsbury, if not further. Once they're finished, you've got Christmas - and the miles of queues for Cribbs Causeway Shopping Centre. Whilst most traffic uses J17, J16 is a popular back route into the complex, which adds to this junction's problems. After the January sales, you might have a brief respite until Easter comes once again.
As mentioned, you will have the ATM works to add to this next year, which could be fun.
Luckily, if you are coming from the M4, or want to do M5S-M4 in any direction, one can use M5 j18a and the M49 (pathetic as it is;) ) to bypass this Bad Junction's sliproads. You'd just be going straight through the middle on the M4 ! :)
When M5 J16 was built, the A38 was a single carriageway road and the surrounding area was fields. Since then the whole area has been massively developed and the A38 has become a major access route into Bristol. J16 is a basic roundabout junction and is quickly followed on the A38 by another roundabout. As both of these are now traffic light controlled to cope with the load, it is no wonder the whole complex is completely overloaded.
Unfortunately, as the whole area is developed, any improvements would require large scale demolition and so is unlikely ever to happen. One way to improve this junction, particularly from the summer Saturday queues, would be to provide another route from the M4 to the M5 around the east and south side of Bristol, but penny pinching on the A4174 has probably ruled out that idea.
Lastly, the M5 north of the Almondsbury interchange didn't open until 1971, so for 5 years, the north side sliproads lead to a field!
There is an obvious cheap-and-nasty solution: build a North-facing half diamond on the M5 at Hortham Lane (the unclassified road bridging the M5 immediately north of all this), stick a roundabout in (or let's be really pathetic: paint a mini-roundabout!) where that joins the A38, then close the links between the M5(N) and the C/D roads. That should simplify things enough to keep it moving.
James' plan would also reduce the possibility of mistakes - travelling from the northbound M5 to the eastbound M4 you need to take the slip road on the left and then bear right. If you bear right too soon however, you end up back on the northbound M5 - it's a long way up to J14 before you can turn round and try again.
As this is now on my way home every week, I feel compelled to give my six penneth. The whole thing suffers from a capacity inadequacy. Two lanes cannot handle the southbound (or northbound) M5 traffic during peak hours (same is true of M4 east or west). An extra lane is the only answer (two hopes), or even better a junction diversion route linking the M49 to the M5 near to Michaelwood (more chance of winning the lottery).
Having used this junction in all directions for the best part of 20 years, I am absolutely astounded that there isn't at least one fatality a month on this junction. Almost every time I pass through it I see a near miss, usually the result of people being in the wrong lane and lurching across the hatched area at the last minute.
My father was part of the team that originally surveyed the junction. He has told me that originally it was supposed to be a 'butterfly' type, but budget constraints reduced it to the 'cross' shape it is today.
When a road is particularly dangerous (as described) it is sometimes worth doing particularly idiotic things just to make it safe.
One suggestion for you to rip apart: Remove the east on / off slip of the A38 onto the M5. This fixes the short interchange problem.
Build a new bridge a sensible distance west along the M5 allowing westbound M5 traffic to turn and come back eastbound. This allows all traffic to access everything, without the short interchange.
It also reduces the complexity of the roundabout, so some of the traffic signals can be scrapped which will ease the flow of traffic. Also consider adding a 4th lane for the entire section between the M4 and new bridge I suggested.
This 4th lane (on the left) is for non M5 traffic, either joining or leaving and connects to the existing M4 connections.
I don't believe I have ever driven through this junction. So perhaps I am not taking something into consideration.
Regarding Andy's idea;
I'm afraid it simply wouldn't work. First, there is no room for a bridge between J16 and J17 - the land to the south of the motorway in particular is very heavily developed. There's also no room for the sliproads on the motorway itself - it would just cause even worse weaving for the whole stretch between the M4 and Cribbs Causeway.
I had to use this junction for the first time recently while returning from Reading, travelling M4 westbound to M5 southbound. And I can quite agree that the C/D carriageway I had to use is a mess!
Since I knew about this junction in advance, I knew I had to move to the right, but there was no indication of where, and I was about to move into the lane that just joined from M4 eastbound when I realized that would be pointless.
It could really do with some advance signage, and longer hatchings, since the lanes are ridiculously wide here for the most part.
For a more ambitious suggestion, I suppose if the M5 was realigned slightly to the northwest there might be room for a pair of one-lane braided sliproads from M5N to the J16 roundabout and back.
Alternatively, scrap the entire junction 16, dual and classify Bradley Stoke Way, and have that link up to a new roundabout interchange with the M4 about a third of the way between this and the M4-M32 junction (such a road could link up to the B4427 too to avoid the motorway restriction problems).
I have used this junction many times, but it was on the last usage I discovered that sat-navs do not understand how the C-D lanes work! It told me to keep right after turning off. It was only AFTER I was part the gore did I realise the lane I was in took me back to the M5. My father-in-law made the same mistake using the same sat-nav.
The problem is the A38 junction - why was it built so close?
Mark has a valid point about sat-navs - they struggle with collector carriageways. I have witnessed them go haywire with the much larger Worsley Braided Interchange.
As for the junction being close - it's an unfortunate by-product of early 1960s thinking that traffic volumes would cope with such short distances - look at how close together junctions in new towns are for example.
It would be hellishly expensive but some kind of slip road braiding would be helpful.
Part of the problem was that the M5 between now junctions 16 and 17 was built as a small bypass of Filton and predates the Almondsbury interchange.
It is akin to the M60 junctions 11 to 13 situation where the local junctions 11 and 13 were part of the original Stretford - Eccles bypass and predate the major interchange at junction 12 (M60, M62, M602, former M63) which had to be shoehorned in afterwards and the existing bypass widened.
A lot of traffic should be removed from this junction all together by building a new motorway east of Bristol, this could connect with the mystery junction on the M4 between Bath and the M32. It could continue north to meet the M5 closer to Michaelwood Services and south to meet the M5 near Clevedon. Any traffic heading to and from London could then miss this busy junction all together.
The M49 does a similar job for traffic travelling between the South West and Wales and I imagine it contributes massively to reducing congestion at Almondsbury (apart from the silly roundabout junction where it meets the M4 - Doh!)
I moved to Almondsbury about 4 months ago and I travel all over the South West for work and this is still the worst part of any journey.
People who use only the M5/M4 think this is bad, try going Northbound from the A38 and attempt to get onto the M5 on any morning when the M4 is jammed down to the M32. Whilst the junction is awful, the thoughtless and horrendous driving tendancies by impatient drivers coming off the M5(N) to join the M4 Eastbound make this junction an absolute death-trap. To get onto the M5 Northbound you have to effectively cross a single file queue of traffic trying to get onto the M4E distributor road, so whilst you cross that first line of traffic to get into clear air for the M5, you will get some idiot come flying down the outside trying to tuck into the M4E collector lane at the last minute and thus taking me or someone else out!!!
The only suggestion I can think of is that M5 traffic should have a separate way to join the A38 at Junction 16 and let the M4 traffic flow freely into either the A38 or the M5.
Fixing this junction would be extremely easy. As suggested, a braided junction would be the best answer.
The model I'd suggest for it is the M8-A720 junction - two slip roads go around the M8 junction to access the the A71.
Similarly, the south-facing sliproads from the M4 can be routed around the A38 junction.
How about this?
Build a half diamond from the A38's bridge over M4 (the bridge is already wide enough for the job), with slip roads facing SE, running alongside but not joining M4E (a la A414/M1 junction), until they join the slips roads to and from the M5. Traffic from M5N wanting to reach J16 would only have to cross SW - S Wales traffic, but since M49 that is easy.
Then you can close off the existing access between J16 and M5N, allowing two lanes for the whole length of the sliproads between London and the SW. J16-M4 traffic is unaltered, but now has more time and less competition for space to negotiate the junction.
At the same time, ideally, the M5 should be upgraded to 4 lanes each way from J17 to J15 (splitting 2 for M4, 2 for M5), and the M4 likewise desperately needs a 4th lane all the way to J19 (it only narrows to 3 lanes for about a mile currently!).
Almondsbury residents would probably take the extra traffic through their village in exchange for safer access to the M5 and M4!
P.S. This scheme could also serve as a decent temporary diversion to create the space for grade separating M5N-J16 from M4-M5 traffic, if that ultimately proved necessary.
My my what a mess, since the opening of the 'Managed Motorway' section here, back in the Spring of 2014, the junctions have become an even bigger horror! The Southbound J16 sliproad is now a mad tango of four lanes, with frantic drivers dashing about trying to understand and comprehend the mad and slap dash signage which adorns them from above. For a moment, one might mistake this slip road as part of the M25 or M62, a true nightmare. I question the effectiveness and validity of the recent 'improvements', especially when I regularly find myself fighting a battle with other road users at rush hour, made worse by the Northerner tourists in the summer, you'd think they don't understand the concept of a slip road! Oh my, will we ever see a real improvement to this travesty of a junction!?
I was once traveling along the M5 northward, and was going to change to the M4 east at this junction. A lorry blocked the M4 exit, by pulling across (without indicating, I hasten to add) 2 lanes, and we had to go up to the next junction, and perform a u-turn.
What I would do is split the 4-lane M5 into 2 2-lane carriageways south of the A38. From the outer lane, a third lane would go to the A38, and then the sliproad from the A38 would split, one lane going to the main M5, the other joining the M5-M4 sliproad. The junction would then remain unchanged. Eh volia! A simple, safe, and easy junction for everybody.