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A rather uninformative page for this has popped up on the HA website. However, the RIS investment plan (p. 40) is a bit more forthcoming:
M42 Junction 6 improvement – comprehensive upgrade of the M42 junction 6 near Birmingham Airport, allowing better movement of traffic on and off the A45, supporting access to the airport and preparing capacity for the new HS2 station.
Given this is already a three-level interchange with a large adjacent partially freeflow interchange to the west and C/D lanes to the east, a 'comprehensive upgrade' could result in something very elaborate.
Note also that this scheme is committed for this road period, i.e. funding is allocated and construction should start by the end of March 2020.
A couple of years ago Solihull proposed replacing the existing J6 with two new junctions, one to the north and one to the south of the existing junction. How this would work with the proximity of J7 and the new service area is anyone's guess...
The whole airport/NEC/M42/A45/(several more minor roads) complex is incredibly confusing as it is at the moment; it's well-signed (although with prism signs; the signs even change over time!) but especially over the airport side of things, it's basically impossible to figure out where you are or where you're meant to go even with a map. (That said, it's conceptually two separate junctions with a small gap between them.)
I suspect an upgrade would make things even more confusing (and it's not quite clear what an upgrade would look like, given that M42 J6 already has an amazingly high standard with many more freeflow links than would be expected in a usual stackabout).
tom1977 wrote:A couple of years ago Solihull proposed replacing the existing J6 with two new junctions, one to the north and one to the south of the existing junction. How this would work with the proximity of J7 and the new service area is anyone's guess...
The obvious change to the north is to use the A452/A446/B4438 roundabout (which is already in the right place) and have only north-facing slips there (although how those would tie into J7 is far from obvious).
ais523 wrote:The obvious change to the north is to use the A452/A446/B4438 roundabout (which is already in the right place) and have only north-facing slips there (although how those would tie into J7 is far from obvious).
I can't see what more can be done beyond more lanes, even that will be a struggle I think.
Perhaps some sort of freeflow A45E -> M42N, closing the NEC access and utilizing the East Way overbridge to create a new NEC access to the east of the junction?
Why does the NEC have so many grade-separated filter lanes anyway? I was never clear on that, and assumed it was something to do with peak capacity (i.e. often there's nobody going to the NEC, but when there is, you often get huge numbers going there all at once).
There are almost too many ways this could be upgraded, e.g.:
- widening of J6 roundabout and approaches - in fact this is already earmarked as part of HS2 (see p. 159 here) though presumably this is separate from the 'comprehensive upgrade'.
- left turn filter for M42Sb>A45Eb
- parallel carriageways on A45 between airport and J6
- loop in SW corner for M42Sb>A45Eb (similar to M62/M57)
- semi-directional ramp for M42Sb->A45Wb, going over or under roundabout
- semi-directional ramp for A45Eb->M42Sb, bypassing roundabout to SW
ais523 wrote:Why does the NEC have so many grade-separated filter lanes anyway? I was never clear on that, and assumed it was something to do with peak capacity (i.e. often there's nobody going to the NEC, but when there is, you often get huge numbers going there all at once).
If you try to drive through J6 when there is a big event on at the NEC, it seriously clogs up the M42 either side of J6. To be fair, there is no way that an upgrade to J6 itself would solve this as the problem lies in getting people into car parks quickly and efficiently.
ais523 wrote:The obvious change to the north is to use the A452/A446/B4438 roundabout (which is already in the right place) and have only north-facing slips there (although how those would tie into J7 is far from obvious).
I think the HS2 line route prevents that option.
Indeed it does, HS2 ploughs through the middle of the roundabout.
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The section between J6 and the Airport is already being widened isn't it once the new bridge is complete?
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There's a glimpse of what HE may have in mind here:
A two junction solution, combining the existing junction with a second junction situated to the south of the existing M42 J6.
Unfortunately, the 'view road project page' link just goes to the aforementioned uninformative scheme page.
If I had to guess I would say that the plan is probably to link the new junction to the adjacent airport interchange. This would allow M42 traffic to reach the airport (and perhaps A45W) without navigating the J6 roundabout. The arrangement would be similar to M25/A13 or M25/Heathrow T5.
What's bothering me is, if you create a new junction to the south of J6, what does it connect to?
The B4102 is too far away to reasonably help out the airport (not to mention that I doubt the B4438 has enough capacity). A connection along the approximate route of the railway would be too close to the existing junction. And if you're connecting to the A45-to-airport flyover, you'd be coming in at the wrong angle. In other words, I can't see an obvious way for a junction to the south of J6 to help out the airport. Maybe there's a non-obvious one. (Perhaps the B4438 will be upgraded?)
ais523 wrote:What's bothering me is, if you create a new junction to the south of J6, what does it connect to?
The B4102 is too far away to reasonably help out the airport (not to mention that I doubt the B4438 has enough capacity). A connection along the approximate route of the railway would be too close to the existing junction. And if you're connecting to the A45-to-airport flyover, you'd be coming in at the wrong angle. In other words, I can't see an obvious way for a junction to the south of J6 to help out the airport. Maybe there's a non-obvious one. (Perhaps the B4438 will be upgraded?)
I was thinking something like this (railway in grey):
Last edited by jackal on Sun May 08, 2016 08:27, edited 1 time in total.
Basically it will connect with a dumbell just North of the B4102 Solihull Rd. Given this is less than a mile from the existing J6 it will obviously need to be worked into the expanded junction complex - maybe something like this:
I think this is about as simple as it can get. Given that this complicates A45<->M42S it could be that something more complex, with braiding or proper C/D lanes, is required.
I can't drive, so when I feel like looking at roads, I do so by bus. One of my common choices for the purpose is the number 900 bus which goes via the airport and railway station, and then onto the A45 east toward Coventry, so it gives a good view of the junction complexes in the area. It says a lot that even though I've looked at maps of the roads around the airport and station repeatedly, and driven it many times, I still get confused as to where I am and which road connects to which. (It doesn't help that many of the flag signs are prism signs. I don't know what the options on them are like; it's most likely to do with dynamically routing vehicles aiming for the A45E/M42 onto either the flyovers from car park 5/6 or onto the main roundabout based on traffic conditions, although I guess it could direct people onto the B4438/A446 for appropriate journeys if the M42 is particularly congested?)
Anyway, M42 J6 is also more complex than is typical, so as a fan of complex junctions, I was a little disappointed when I realised that the two junction complexes didn't actually connect or interact in any way other than weaving. It looks pretty much inevitable that the two will end up merging somehow as a result of these changes, leaving me both hopeful and a little scared.
Meanwhile, the junction complex containing M42 J7 – again, mostly independent unless you count the A446 as being part of the junction complex, which it arguably is – has been one of my favourites for a long time (I admire the way that it provides for every movement over a large area whilst not allowing you to get stuck in a loop). If that gets dragged into this mess somehow too then we'll probably have the indisputable most complex junction in the UK. (Spaghetti Junction is already pretty tame by comparison, for example.)
In other words, I'm really looking forward to actually seeing the plans.
ais523 wrote:I can't drive, so when I feel like looking at roads, I do so by bus. One of my common choices for the purpose is the number 900 bus which goes via the airport and railway station, and then onto the A45 east toward Coventry, so it gives a good view of the junction complexes in the area. It says a lot that even though I've looked at maps of the roads around the airport and station repeatedly, and driven it many times, I still get confused as to where I am and which road connects to which. (It doesn't help that many of the flag signs are prism signs. I don't know what the options on them are like; it's most likely to do with dynamically routing vehicles aiming for the A45E/M42 onto either the flyovers from car park 5/6 or onto the main roundabout based on traffic conditions, although I guess it could direct people onto the B4438/A446 for appropriate journeys if the M42 is particularly congested?)
Anyway, M42 J6 is also more complex than is typical, so as a fan of complex junctions, I was a little disappointed when I realised that the two junction complexes didn't actually connect or interact in any way other than weaving. It looks pretty much inevitable that the two will end up merging somehow as a result of these changes, leaving me both hopeful and a little scared.
Meanwhile, the junction complex containing M42 J7 – again, mostly independent unless you count the A446 as being part of the junction complex, which it arguably is – has been one of my favourites for a long time (I admire the way that it provides for every movement over a large area whilst not allowing you to get stuck in a loop). If that gets dragged into this mess somehow too then we'll probably have the indisputable most complex junction in the UK. (Spaghetti Junction is already pretty tame by comparison, for example.)
In other words, I'm really looking forward to actually seeing the plans.
All we have to go on at the moment is the description mentioned above:
A two junction solution, combining the existing junction with a second junction situated to the south of the existing M42 J6 (emphasis added)
From this I doubt that the current J6 will expand west along the A45 or north along the M42. There are, however, likely to be slips extended to the east (as at present) and to the south (linking to the new junction and service station), so it will be pretty complex.
You could also argue that the whole tangle between M42 J7 and J9, and M6 J3a and J4a, is already the most complex junction complex in the UK.