M5 J11A - Why is it so BIG ?

[Derek_alt]

Why on earth is the M5 J11A so massive ? It seems amazingly over-built/designed for what it is currently doing.
Also, I notice that the J11 signs with the white M5 blocks are having new signs erected in front of them...
Derek, Leicester

[Jimbo]

M5 J11A appears on CBRD's Bad Junctions pages and one of the original designers gives reasons why it was designed the way it was. Basically, it may not look busy, but it is, particularly in rush hour, and can agree with this having driven through it a few times during rush hour.

It may be a bit over-engineered, but so what. We spend an awful lot of our time complaining about under-engineered junctions, so we shouldn't be complaining about ones that do their job well. I bet many people would love a few freeflow links on their local junctions !!!

Jim.

[Derek_alt]

Myself included Jim, as the M1 J21 is right near me. I wasn't complaining at the size or anything like that, it just seemed overengineered, especially when compared to the dumbell junction at J12...

[Jimbo]

Ah the story of J12 is an interesting and puts J11A into context a little more.

When the M5 was first built in the late 1960's, Gloucester was served by the 3-level stack J11 (with the A40) and J12, which was originally built as south facing freeflow slips. This meant that all traffic heading north from Gloucester had to go through Gloucester to J11. This is a real pain, particularly as there is a lot of industrial and commercial properties on the south side of the city, which meant a lot of traffic around the A38 ring road (not a ring and mostly S2).

When J11A was built in the early 1990's (or was it late 1980's ??) as part of the A417 upgrade, it was built to solve some specific problems, with some freeflow slips on the busiest flows, leaving the others to J11. It did nothing to help the problems with J12 because it was really too close to J11.

J12 was finally upgraded to all directions in 2002 when the south-facing freeflow slips were replaced with the current dumbell junction. You can see the difference in aims between J11A and J12 - J11A had some specific requirements and they were well met with the current design. The only aim for J12 was a full junction and that was done as cheaply as possible (although the actual implementation was a little suspect - they bult 1 new bridge and demolised the 2 old bridges !!).

It is interesting to note that out of the 3 M5 junctions, both J11 and J12 suffer from peak-hour congestion, but J11A handles it fine. It is also worth noting that J11A has the only freeflow slips of any significance (there are couple of minor ones on the Quedgeley bypass) in the whole of Gloucester, and it shows because it is the only junction in the whole of Gloucester that works well.

With J11A, it looks like they could have done a lot more with the space, but they had the space and there was no real justification for doing more so whay spend extra money. They could have just used a roundabout junction, but that would now be horrendously congested just like all the other roundabout junctions in Gloucester. If all the other junctions in Gloucester had been implemented properly, J11A would look fairly normal.

Jim.

[jamesd]

Hmm, been through J11A a few times going M4W-M5N via A417/9 a few times, but never bothered to have a look at the map. What a strange junction. Seems odd they didn't tie together the slip for "M5N->A417E " with the one for "M5S->A417E". Is there a filter lane on the roundabout?

Accessing M5S can't be easy, from both directions you're turning the wrong way at the roundabout.

[Truvelo]

I've been doing some research on this junction following the last comment on this CBRD page. One of the people who designed the junction mentioned a simpler junction was originally planned so some investigating at archives has revealed a lot of finds.

Firstly a bypass for Brockworth was planned in 1987 along the same route as the current bypass but with a simple roundabout GSJ for J11a, an at-grade roundabout at the A46 and a gap in the central reservation for Dog Lane just before the dual carriageway ends. The orders are attached to the plans which means it must have been close to going ahead. For some reason nothing happened and in 1991 a revised scheme was planned along the same alignment but with no junction at Dog Lane, a roundabout GSJ at the A46 and four options for J11a. One is a 3 level stackabout and three are partial freeflow designs. One of the designs was the preferred option and it's this that will be obvious to anyone who's seen a map of the junction.

I've been rattling on about schemes planned years ago with full separation only to be built in the 1990s with at-grade junctions on the cheap. There are numerous examples: Bilston Link, Black Country Spine Road, Wilmslow Bypass, A444 Coventry, Gloucester Northern Bypass to name a few. This bucks the trend with the original plan being el cheapo at-grade but built in the 1990s with GSJ's. I wish more roads were built this way.

1987 design


1991 options

[A303Chris]

I think the the stackabout would have been the best option but as you say it was nice that an at grade was upgraded to a GSJ route

[fras]

Not forgetting, of course, that if they ever complete a dual carriageway connection at Birdlip to the A417 dual-carriageway, this junction will be ideal, whereas a roundabout would have caused delays.

I suppose this link was cancelled by the last Labour lot, who seemed to have cancelled off almost all road building and cut the strategic road network by a third too in their time in office. Of course the previous Tory (John Major) government were pretty useless too. It was Mr Kenneth Clarke, no less, who said "why build more roads, they only fill with traffic" !! Wasn't this the mob who put in the A14/M6/M1 parody of a junction ?

[Owain]

Not forgetting, of course, that if they ever complete a dual carriageway connection at Birdlip to the A417 dual-carriageway, this junction will be ideal, whereas a roundabout would have caused delays.

I have always assumed that it was precisely for that reason, coupled with a possible upgrade to the A436. But even so, the 'loop-the-loop' slip road that you have to follow if travelled from A417 westbound to M5 northbound is quite unusual for UK junctions.... after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

[Keiji]

after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

Wasn't that done just so they could add the services?

[Truvelo]

I think the M5 widening had a bigger influence as the extra lane would have made the loop even tighter, just like the loops at J5 were removed.

Documentation from 1978 makes it clear the Brockworth scheme was part of a Cheltenham Southern Bypass which would have involved upgrading the A436. I haven't yet discovered when plans for Brockworth changed from a Cheltenham Bypass to an A417/A419 upgrade but by the time the bypass was built the A417/A419 route become the dominant route. The idea of an A436 upgrade still floats around but is now a strictly local authority scheme.

[JamesA44]

But even so, the 'loop-the-loop' slip road that you have to follow if travelled from A417 westbound to M5 northbound is quite unusual for UK junctions.... after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

I love that loop!

[Owain]

after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

Wasn't that done just so they could add the services?

I read something somewhere on the web (CRBD?) about it being removed because lorries were tipping over on it.

But even so, the 'loop-the-loop' slip road that you have to follow if travelled from A417 westbound to M5 northbound is quite unusual for UK junctions.... after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

I love that loop!

I agree that I would much rather have a loop-the-loop than a "give way"/roundabout solution. Where M-ways are concerned, free-flow is always better than give-way.

[JamesA44]

after all, they actually removed a trumpet from the M50 junction a few miles up because they thought the loop-the-loop to be too sharp!

Wasn't that done just so they could add the services?

I read something somewhere on the web (CRBD?) about it being removed because lorries were tipping over on it.

Like this?

It was to do with junctions 6 to 8 being widened - but that was a welcome side-effect.

[Owain]

Yeah, that'll be it.

[B1018 A120 M11]

I read something somewhere on the web (CRBD?) about it being removed because lorries were tipping over on it.

Like this?

Wow, that's an amazing photo, and an even more interesting *photostream*. If you go left and right from the original linked pic of the overturned Frigoscandia lorry, there are loads of pics of the M5 pre-widening, or while the widening was going on, which I'm guessing must date from the late 70s/early 80s?

Of particular interest to me, there are some very detailed shots showing what the Strensham freeflow loop looked like at M5 Junction 8 from various angles and directions of travel before it was converted into the current thoroughly dull roundabout. My uncle and aunt lived just outside Hereford from the late 60s until two years ago, and my family used to go down the M50 from the M5 all the time when I was a kid in the late 70s to visit them. But by the time I was properly aware of the junction, it was the early 90s and the current layout was in place. I was amazed to learn on here that it was a loop back when I would have been travelling on it. Unfortunately, I have no memory of it being freeflow... but these photos get me closer to appreciating what it must have been like.

Back on the main topic, I've used M5 J11A a lot in recent years and it is a maddening junction. The thinking of the designers that you would 'simply use other junctions' for the missing movements consigns a lot of people to miserable trawls through clogged-up bits of Gloucester to reach the motorway... and I thought part of the reason for building a Junction 11A in the first place was to deal with that problem! [slaps head]

To take more of a 'glass half-full' attitude, though... at least there is *some* freeflow at the junction...!

[A303Chris]

I read something somewhere on the web (CRBD?) about it being removed because lorries were tipping over on it.

Like this?

{Wow, that's an amazing photo, and an even more interesting *photostream*. If you go left and right from the original linked pic of the overturned Frigoscandia lorry, there are loads of pics of the M5 pre-widening, or while the widening was going on, which I'm guessing must date from the late 70s/early 80s?/quote]

I think you find it was early 90's. I remember going up it in the late 80's and it was still 2 lanes. In fact this old thread gives all the details. J4 to J6 widened late 80's, J6 to J8 widened early 90's

[Richardf]

I think the issue people have with this junction is that it might be a free flow or mostly free flow junction but for the amount of space it takes up its not that well designed. You feel something better could have been designed and built here. Maybe the A417 could have flowed directly to and from the M5 with a TOTSO to continue on into Gloucester?

I feel the roundabout part of it is the problem, without it a much better free flow junction design could have been used. Surely access to the business park could have been provided elsewhere or in some other way?

[jackal]

It's not just access to the business park but also to a swathe of eastern Gloucester, and without it you'd have heavy rat running along Ermin Street. Essentially the Brockworth Bypass would not be a bypass without it.

The key movement pairs are M5-M5, A417-A417, M5 north-A417 east, M5 south-A417 west. Seven of these eight movements are freeflow, and the one that isn't (A417 eastbound to M5 southbound) is a simple left turn at a roundabout. Given the junction achieves all of this while also providing local access it has to be considered an elegant design. By comparison the lazy option of the stackabout would conflict the heavy strategic right turns that are separated here. Nice to see designers earn their fee.

That said, filter lanes at the roundabout so A417 eastbound to M5 southbound and M5 northbound to A417 eastbound were freeflow would be welcome. I also wonder if the A417 roundabout immediately to the west is needed; only a westbound onslip from the business park really seems necessary as the other movements are catered for at J11a.

[fras]

The replacement for the A417 where it reverts back to single carriageway at the Cowley Wood roundabout will eliminate the rather lengthy queues of traffic before and after this roundabout as far as the Air Balloon pub. I wonder if this has been considered and any possible changes to Jn 11a. I came this way yesterday, and prayed for an early start to the works.