A417 Missing Link campaign!

[SouthWest Philip]

I would think it would be possible to tie both junctions south of the Air Balloon into one dumbbell junction.

Out of curiosity, how does the severity of the proposed loop compare with the big bend on the M90 south of Perth?

[roadtester]

Not sure about the specific comparison with M90 but I'm very familiar with the A417 and I woudn't be surprised if the scheme would result in just about the steepest and sharpest-radiused modern D2 in the UK. I'm hard pushed to think of anything comparable.

That said, it would be a big improvement and I don't think the gradient part of things would be an issue at all for most modern cars.

[M4 Cardiff]

That said, it would be a big improvement and I don't think the gradient part of things would be an issue at all for most modern cars.

but for HGV's?

[Bryn666]

Crawler lane... it undoubtedly will be a 50 limit if built.

[wrinkly]

Even stranger than there being no slip roads from the A417 n/w bound onto the A436 and into Cheltenham, except via Birdlip - there are two slip roads from the A417 south/east bound onto the A436. Why is the second necessary?

What are you counting as the first one? Going up Crickley Hill before the Air Balloon? I don't think there's any exit there - maybe it's an issue of levels. I think the U-turn exit slip is the first exit after the A46.

Out of curiosity, how does the severity of the proposed loop compare with the big bend on the M90 south of Perth?

This is considerably sharper than the M90. The M90 is NSL isn't it?

[t1(M)]

Even stranger than there being no slip roads from the A417 n/w bound onto the A436 and into Cheltenham, except via Birdlip - there are two slip roads from the A417 south/east bound onto the A436. Why is the second necessary?

What are you counting as the first one? Going up Crickley Hill before the Air Balloon?

It's not a very clear map, but there appears to be a slip road from the top of the hill towards the roundabout where the A436 meets Leckhampton Hill. If it doesn't connect from the A417, what is it?

[wrinkly]

I think it's tolerably clear if you view the scaleable map at high magnification, especially if you also compare it with OS mapping.

A section of the present A417 remains open, on the north side of the proposed A417, to retain connectivity to some minor roads and buildings. It's shown in buff colour. Near the top of the hill it's realigned, and there is shown in dark green. It connects to the replacement roundabout but not to the proposed mainline.

[A320Driver]

The geology is difficult here, but not insurmountable for a tunnel. Heck, if we can build a tunnel under the sea, I really don't see what, given enough concrete, the issue is with the water table here. Apart from money!

This scheme has the makings of another Twyford Down. Build the tunnel or reap the consequences for 20 years. Doing nothing would be better, IMO.

[roadtester]

The geology is difficult here, but not insurmountable for a tunnel. Heck, if we can build a tunnel under the sea, I really don't see what, given enough concrete, the issue is with the water table here. Apart from money!

This scheme has the makings of another Twyford Down. Build the tunnel or reap the consequences for 20 years. Doing nothing would be better, IMO.

If I remember correctly, the estimated cost of the tunnel was in the £1 billion range, and there would still have been quite a gradient.

That said I agree on the Twyford Down comparison - you're talking about potentially modifying the skyline of the Cotswold escarpment (actually, I think the road would be quite well hidden) and the locals are probably among the most articulate and well-to-do in the country and can probably be relied upon to kick up an enormous fuss if stirred.

[Ritchie333]

I have gone past the Air Balloon on several occasions to Wales and Ireland. I worked out it was more cost effective to cross the Severn at Gloucester than use the M4, and the A436 / A417 is part of this route. The fact it involves the handbrake turn at M50 J3 later on is, of course, pure coincidence.

The view from the top is absolutely stunning, so I think any plans are going to have a tough time ahead against anyone with environmental concerns. Which is of course why it hasn't been done until now.

Incidentally, has anyone tried the old Roman Road from Birdlip down to Gloucester? It wasn't even in the main road when numbers were first handed out, and it certainly isn't now. I don't think I've experienced quite an unexpectedly steep drop since I did the A39 along the north Devon and Somerset coast.

[c2R]

That said I agree on the Twyford Down comparison - you're talking about potentially modifying the skyline of the Cotswold escarpment (actually, I think the road would be quite well hidden) and the locals are probably among the most articulate and well-to-do in the country and can probably be relied upon to kick up an enormous fuss if stirred.

Perhaps use the same method as the A505 tunnel at Baldock - Cut a giant wedge out of the hill, put a couple of concrete tunnels in, and whack the soil back on top to preserve the skyline.
http://www.bbc.co.uk/threecounties/cont ... y.shtml?19


However, I'd rather the loop method was used and construction commenced than doing nothing and waiting another decade or two before eventually building the loop anyway.

[roadtester]

I think it's the sort of thing - blasting a dual carriageway through the crest of the escarpment - that objectors can probably make sound terrible, but in practice the existing road is quite well concealed, especially from below, thanks to plenty of vegetation and I think perhaps some cutting.

This is the view approaching the top of the escarpment with the Air Balloon ahead on the right:

https://www.google.co.uk/maps/@51.84323 ... e0!6m1!1e1

The new scheme would probably have to involve the removal of many of the trees beyond the roundabout, but up to that point could probably be kept well hidden. The existing three lanes on this stretch could probably be widened to D2 without destroying too many of the established trees, which are set well back from the road. Also, the road could probably be lowered a bit to ease the gradient and also to take it further out of view, again without taking out too much of the vegetation.

[Stevie D]

Not sure about the specific comparison with M90 but I'm very familiar with the A417 and I woudn't be surprised if the scheme would result in just about the steepest and sharpest-radiused modern D2 in the UK. I'm hard pushed to think of anything comparable.

How about A171 up Birk Brow? (OK, may not fit your definition of "modern")

[jackal]

Since the last post in this thread, the scheme entered the programme for 2020-25, with a consultation expected later this year and local politicians hoping for a 2020 start of works. Apparently HE are looking at a scheme using tunnels, costing around £500m, as an alternative to the £250m loop scheme discussed above.

http://www.gloucestershirelive.co.uk/ne ... ers-258271

[Berk]

I'd wondered if the scheme had died, or become a victim of cost-cuts. It's all been very quiet...

Not sure about the specific comparison with M90 but I'm very familiar with the A417 and I woudn't be surprised if the scheme would result in just about the steepest and sharpest-radiused modern D2 in the UK. I'm hard pushed to think of anything comparable.

That said, it would be a big improvement and I don't think the gradient part of things would be an issue at all for most modern cars.

Most of the current road has pretty sharp gradients doesn't it??

It might even be a call for split carriageways.

[ScottB5411]

This is one scheme that certainly needs doing properly and not a "bodge". I'm surprised that they are still pushing tunnels given that the UK is scared of them.

[wrinkly]

A lot of stuff about the previous studies is still online. The links on this archived page (or at least the one or two I've tried) still seem to work:

http://webarchive.nationalarchives.gov. ... /3593.aspx

[jackal]

Interesting. The study in the noughties looked at three options:

(1) surface dualling with air balloon at-grade. £26.9m (1998 prices!), 2.39 BCR (low growth).
http://webarchive.nationalarchives.gov. ... re_5_1.pdf

(2) surface dualling with air balloon GSJ. £36.9m, 3.09 BCR.
http://webarchive.nationalarchives.gov. ... re_5_2.pdf

(3) 2.8km bored tunnel. £144.3m, 0.88 BCR.
http://webarchive.nationalarchives.gov. ... re_5_3.pdf

Option 1 was rejected as inadequate in transport terms:

14.6 Whilst it is recognised that this option is buildable, economic and provides some congestion relief, it does not provide a long term solution for road borne traffic within the study area due to limited capacity at the Air Balloon junction. In addition, there are serious concerns over safety on certain aspects of the layout which could not be overcome by careful detailed design. Although this option would improve the majority of the route the Air Balloon junction would continue to be a bottleneck and present safety problems. Whilst detailed design and modelling may be able to extend this congestion-free period by a few years, it is unlikely to provide a long term solution or overcome the safety concerns This option therefore fails to meet 2 of the main tenets of this study.

As well as being most expensive and poor value, the hydrogeology for option 3 was a 'showstopper':

14.19 Given the nature of the underlying geology, there is a real possibility that to accurately define and model the groundwater regime over such a wide area will prove so difficult and problematic that, even after completion of the significant additional work, it may not be possible to be definitive about the impact of the tunnel. It is uncertain that even following this additional work the risks to the aquifer could be reduced to a level that would be acceptable to the Environment Agency, and for them to remove their objection. In these circumstances, the Environment Agency would be unlikely to withdraw their objection and would hold the Highways Agency legally responsible should environmental problems arise during construction and operation of the tunnel The Highways Agency could not accept such a condition.

14.20 It is recommended that at this stage no further assessment of this option is carried out.

This left option 2 as the last option standing. The concept is broadly similar to the contemporary loop option, but rather than a large radius offline loop it simply 'cut the corner' between the two arms of the A417 with a tighter turn. It also looks like it may have had offside entries and exits.

It sounds like the modern tunnel option may be different to option 3 as well. The tunnel lengths (2.8km versus 1.5 miles) don't match up, and the press report mentions cut and cover as well as boring, albeit in garbled fashion.

[Richardf]

Would a standard/conventional grade separation of Air Balloon work? Even if it meant the A417 having to TOTSO at this point? Not ideal, but probably quite a cheap option, perhaps more so than the Loop idea and certainly more so than tunnels.

I am thinking this would then future proof the area so that the A436 could be improved as a southern bypass for Cheltenham, (Becoming the A40 in the process).

Any other solutions/ways Air Balloon could be grade separated and keep the A417 as the mainline? When the mainline turns a corner at an at grade junction, i have never worked out satisfactory ways to grade separate them.

[jackal]

Would a standard/conventional grade separation of Air Balloon work? Even if it meant the A417 having to TOTSO at this point? Not ideal, but probably quite a cheap option, perhaps more so than the Loop idea and certainly more so than tunnels.

If you mean the A417 still has to navigate an at-grade junction then clearly that would not be acceptable. If you mean the A417 has a freeflow TOTSO that's what option 2 mentioned above does.

Any other solutions/ways Air Balloon could be grade separated and keep the A417 as the mainline? When the mainline turns a corner at an at grade junction, i have never worked out satisfactory ways to grade separate them.

You just make the mainline turn the corner. To maintain NSL it needs a lot of space as with the loop option.