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Richardf wrote: ↑Fri Aug 30, 2019 19:54
Consider the history of the junction. The present layout was designed to give access to the Bullington Cross Inn, while making the junction as freeflow as possible. If the pub hadn't been there a much better layout would have been used. The fact that the pub no longer exists doesn't really change things.
Is there any evidence for that or is it just an urban myth? I ask because it sounds an awful lot like "the M62 was routed around a stubborn farmer".
The publicity at the time suggested the main priority was keeping the A34 on a gentle gradient, which would help explain the layout. There was also a lot of talk about keeping costs down. I'd suggest the fact the chosen design could easily factor in the pub was a mere coincidence.
If that’s true, I find it odd that there is a single free-flow for A34N-A303W. That means that someone took the care to design it, and it could easily be accommodated within the gradients.
If that was the case, surely a conventional roundabout interchange wouldn’t have been too much to ask eventually?? Even if the current layout had to remain in place as a ‘temporary’ layout. I even wonder if a compact GSJ could’ve allowed A34S traffic to cross the carriageway, and access the free flow westbound sliproad.
I’m sure they would never have expected the layout in place in 1981 to still be there in 2019.
jackal wrote: ↑Fri Aug 30, 2019 13:22
Just needs two new bridges to be rearranged as a full freeflow partially-unrolled cloverleaf. A third bridge would be needed for a new A30 GSJ to the south.
a34 a303 big - Copy.jpg
How much do you think it could cost to improve this junction??
I'm not sure if a free flow junction is really possible at this junction. It could be done, but it would be expensive and some movements unjustified for full free flow. This is my solution, which is just a simplified version of the current junction. The roundabouts would be larger than the current ones and a new free flow loop would be added.
"All roads lead to Rome" What about the M25?
The A205 - The road to... oh wait I should've turned right back there!
MotorwayPlannerM21 wrote: ↑Sun Sep 01, 2019 21:08
I'm not sure if a free flow junction is really possible at this junction. It could be done, but it would be expensive and some movements unjustified for full free flow. This is my solution, which is just a simplified version of the current junction. The roundabouts would be larger than the current ones and a new free flow loop would be added.
While the extra free flow links are a plus, this plan looks more complicated than the current junction!
It isn’t really, in fact it’s quite simple!! I remember the first time I used the junction making some checks, so I could tell the right way to go round it.
Richardf wrote: ↑Sun Sep 01, 2019 22:24
While the extra free flow links are a plus, this plan looks more complicated than the current junction!
It may look complicated, but I believe navigating it would be simpler than the current junction (and a lot safer). All of the link roads within the junction are straight and perpendicular to each other. The movements are a lot less circuitous as most of the LILO slip roads have been removed - the only one that remains is the access to/from the A303 westbound carriageway. The on slip here is only for traffic from the A30 so wouldn't be very busy and retaining the loop here is the simplest way to do it.
"All roads lead to Rome" What about the M25?
The A205 - The road to... oh wait I should've turned right back there!
How about this? Free flow links for Andover-Winchester along the old railway line. New Eb-Nb slip road with a decent length of third lane up the hill on the A34. Longer slips and enlarged roundabout on the eastern side
The partially unrolled cloverleaf with direct links on the A19/A66 junction at the approach to the Tees Viaduct works quite well given the volume or traffic and the relatively high amount of turning traffic. It looks complex but in practise is quite easy to use. The main thing that causes problems is the occasional high sided vehicle falling over on the A19 S to A66 W loop. https://www.google.co.uk/maps/@54.56250 ... !1e3?hl=en
AADF on the A19 is above 100k and its around 60 on the A66 west of the junction and 80k to the east
Richardf wrote: ↑Sun Sep 01, 2019 17:17
I realise the tunnel is the plan, I'm just looking at alternatives as I am not a fan of the tunnel scheme. A southern diversion would be my preference as if done right it would help Salisbury as well. North to Larkhill is another alternative which could work but would have zero benefit for Salisbury.
I am aware of the nature of the A338, I wasn't thinking of an online upgrade but rather an offline improvement of the route, probably to the north past Boscombe Down and Porton. Past Salisbury itself I envisage a route some distance north of old sarum (sufficiently concealed to blend into the landscape), and meeting the A36 somewhere near Stapleford.
I'm afraid I'm not terribly optimistic about the tunnel going ahead, something will happen to take things back to the drawing board, when TPTB will have to look again at other options.
The tunnel plan is contingent on a Government spending review going ahead, The PAC has told the government commitment needs to be made to it this year or it won't go ahead. Its difficult to forecast with Brexit swallowing up every inch of government bandwidth.
How much turning traffic is there actually, to make further improvement at Bullingdon Cross worthwhile?
I've used the junction many times in both directions, but never have I actually had cause to turn at it. The only real route requiring traffic to turn would be between Andover and Winchester and the south coast.
c2R wrote: ↑Mon Sep 02, 2019 15:02
How much turning traffic is there actually, to make further improvement at Bullingdon Cross worthwhile?
The problem is not so much that there is a lot of turning traffic, but there is too much for the tiny elements that make up the current junction. It is designed like a compact GSJ you might find serving a tiny bypassed village.
The sub-standard junction isn't itself a problem because in theory you can mitigate against most of the danger by telling people to slow down. The real danger is trying to join the dual carriageways, especially the A34, from what is basically a standing-start. When it first opened the roads were quiet enough that joining the main carriageway wouldn't have been that difficult, but now things have really changed. In that respect you could make life a lot easier purely by widening the A34, though that would hardly be an easy solution either.
With regards to the suggestions above, a key point to remember is how on earth it will be built, if you are planning on taking an existing sliproad and basically lowering it. Will it be possible to widen the cutting that the link road is in without using temporary traffic lights? And would that not cause traffic to queue onto the A303?
What would you do with the A303 westbound to A34 southbound movement? It is currently the alternative route for a long length of the M3, though many would argue it doesn't need to be.
It is a very difficult one to solve - but then that's what SABRE is all about!
jackal wrote: ↑Sun Sep 01, 2019 12:08
In archaeological terms cut and cover is pretty much the worse thing you could do due to the vast earthworks relatively near ground level.
The bypass towards Salisbury has also been assessed many terms and is not a viable solution, not least because environmental impacts would be vastly higher. Look how much new road through countryside it requires compared to the proposed route.
Yes but the point is there are no "vast earthworks" to be disturbed if an on-line dualling exercise was carried out with the existing plus new carriageway sunk into a 5-7 metre cutting and then covered as per the Holmsdale Tunnel on the M25 - so grassed back over. Provided any excavation of the cutting was carried out carefully and with any artefacts properly recovered there seems no reason why on-line dualling in a cut-and-cover shallow cutting could not have the landscape 99% restored to how it was? Only vastly improved because a noisy trunk road will have been removed from view and direct earshot of the monument.
It can't of course be that simple or it would be the solution and they would have got on with it. So what is the proper reason?
c2R wrote: ↑Mon Sep 02, 2019 15:02
How much turning traffic is there actually, to make further improvement at Bullingdon Cross worthwhile?
I've used the junction many times in both directions, but never have I actually had cause to turn at it. The only real route requiring traffic to turn would be between Andover and Winchester and the south coast.
You don’t believe that traffic will be approaching from the north/Midlands, heading for Devon and Cornwall??
Johnathan404 wrote: ↑Mon Sep 02, 2019 15:10
The problem is not so much that there is a lot of turning traffic, but there is too much for the tiny elements that make up the current junction. It is designed like a compact GSJ you might find serving a tiny bypassed village.
Indeed.
The sub-standard junction isn't itself a problem because in theory you can mitigate against most of the danger by telling people to slow down. The real danger is trying to join the dual carriageways, especially the A34, from what is basically a standing-start. When it first opened the roads were quiet enough that joining the main carriageway wouldn't have been that difficult, but now things have really changed. In that respect you could make life a lot easier purely by widening the A34, though that would hardly be an easy solution either.
IMO, the worst joining movement isn’t the A34N, but A303W. As I related earlier, a lorry managed to pass the A30 junction, effectively bringing traffic in the A303 queue to a near standstill. There was one car in front of me behind the lorry.
I declined to follow, as it would’ve meant a dangerously low joining speed (10-20mph, lane 1 only). I therefore ambled up the slip from the T-junction at 15-20, until I was near the top, able to turn, observe, and floor it into lane 2 (joining around 50-ish and able to take it from there).
With the A34, I’ve never had any trouble joining at that sort of speed, and usually a straight run too.
jackal wrote: ↑Sun Sep 01, 2019 12:08
In archaeological terms cut and cover is pretty much the worse thing you could do due to the vast earthworks relatively near ground level.
The bypass towards Salisbury has also been assessed many terms and is not a viable solution, not least because environmental impacts would be vastly higher. Look how much new road through countryside it requires compared to the proposed route.
Yes but the point is there are no "vast earthworks" to be disturbed if an on-line dualling exercise was carried out with the existing plus new carriageway sunk into a 5-7 metre cutting and then covered as per the Holmsdale Tunnel on the M25 - so grassed back over. Provided any excavation of the cutting was carried out carefully and with any artefacts properly recovered there seems no reason why on-line dualling in a cut-and-cover shallow cutting could not have the landscape 99% restored to how it was? Only vastly improved because a noisy trunk road will have been removed from view and direct earshot of the monument.
It can't of course be that simple or it would be the solution and they would have got on with it. So what is the proper reason?
As already stated. 7m deep by 30m wide by 2km long is a huge cutting and as it's at the surface where the archaeology is, much more harmful than a bored tunnel.
c2R wrote: ↑Mon Sep 02, 2019 15:02
How much turning traffic is there actually, to make further improvement at Bullingdon Cross worthwhile?
I've used the junction many times in both directions, but never have I actually had cause to turn at it. The only real route requiring traffic to turn would be between Andover and Winchester and the south coast.
You don’t believe that traffic will be approaching from the north/Midlands, heading for Devon and Cornwall??
I can't imagine that much from north of Leicester would go that way, and purposely suffer the delays at Stonehenge and the blackdown hills, instead of going straight down the M5, no...
MotorwayPlannerM21 wrote: ↑Sun Sep 01, 2019 21:08
I'm not sure if a free flow junction is really possible at this junction. It could be done, but it would be expensive and some movements unjustified for full free flow. This is my solution, which is just a simplified version of the current junction. The roundabouts would be larger than the current ones and a new free flow loop would be added.
You would probably have to reroute the A30 and the Tidbury Farm access lane to seperate junctions with the A303.
RJDG14 wrote: ↑Mon Sep 02, 2019 17:41
You would probably have to reroute the A30 and the Tidbury Farm access lane to seperate junctions with the A303.
Why? The whole point of my design was to retain all the accesses. Re-routing those access would just add extra cost. The only reason to reroute the A30 and farm access would be if you're making a full free flow junction, so the recycling site would also have to go (perhaps by CPO if it comes to it). If the A30 was rerouted to, say, the Micheldever junction, then how would traffic from the A34 SB reach the A30?
"All roads lead to Rome" What about the M25?
The A205 - The road to... oh wait I should've turned right back there!
After sitting there for 10 minutes without a chance to escape last week, the A350 / A303 junction needs redesigning. Turning left out of there is a gamble, turning right is near impossible without blocking the eastbound traffic in order to get into a gap going west. And that was at 3pm on a quiet Monday afternoon.
