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roadtester wrote: ↑Sat Sep 28, 2019 22:12
The green bridge looks like a pretty extravagant structure for something that would have been regarded as a nice-to-have add-on not so long ago.
The scheme as a whole looks incredibly impressive in the visualisation videos - they've done really well to come up with something that looks so workable in difficult while avoiding the need for tunneling as per previous proposals.
I agree, the whole scheme looks very impressive to me. Also means the whole A417-419 route is pretty much grade-separated apart from a few minor accesses and the Seven Bridges junction.
In a perfect world it would be lovely to see these addressed the whole route given a single number. Maybe even an (M) at some point...
Looks like quite a good scheme- as others have said that green bridge looks insane!
My main criticism is that eastbound climbing lane looks like it wants extending all the way to the Cowley junction.
Also the entire scheme is in cutting so a massive earthworks operation!
The green bridge is needed though, when I visited I drove across to either side rather than risk walking!
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DB617 wrote: ↑Sun Sep 29, 2019 00:18
Where does the old line of the S3 A417 up the escarpment fit into the scheme during construction? It's been fascinating to watch how the A465 being kept open has had to be incorporated so heavily into the project management at each stage of that build. It almost appears as if underneath the green bridge, the old A417 runs up between the edge of the cutting and the edge of the retaining wall, sandwiched by the green bridge pillars.
There seems to be an LAR that runs from the roundabout to the dogleg that may give Dog Rd its name. But it's much narrower than the current A417 - probably S1. See drawings below.
This LAR handles access to properties on the north side of the A417. On the south side Crickly Hill Tractors is simply LILOed onto the westbound carriageway, which would be a barrier to the expressway receiving motorway designation.
I think that is indeed the remains of the old road. Which probably explains how access will be maintained during the scheme. It'll probably be hugely disruptive, though, as the S3 will probably be reduced to S2 once digging starts.
Yes, if you look at the video from around 1.35 (and especially 2.00) the S1 LAR seems to be the remnant of a wider, partially grassed over road.
This may also explain why the green bridge is longer than the final configuration requires - so the old A417 can still run while the bridge and new A417 mainline are constructed.
The proposed scheme, on the whole, is good but for the negative impact on the A436.
Aside for the increased distance for the not insignificant east-west flow (effectively the Cheltenham bypass for the A40), the proposed junction layout for the A436 introduces a conflict where westbound and eastbound traffic have to cross each other reminiscent of the failed layout at the M40/A43 Cherwell Valley junction.
I have wondered whether it might be possible to retain the existing road up the hill to the Air Balloon as an eastbound off slip? If the bridge option was chosen to retain the current A417 from the Air Balloon towards Birdlip, it might be possible to add a loop from the A436 to A417 for westbound traffic? Other movements could be catered for via the Cowley junction and retaining the old Birdlip bypass.
Having said that, I guess removal of the old road is a decision that has been taken to justify the environmental impact of the new road. It also looks like there is no plan to reconnect the old road eastwards from Birdlip with the current A417 despite the proposed removal of the current bypass?
Actually, having just viewed the visualisation video, I have a couple more observations (minor gripes?)...
The plan to end the third lane (additional overtaking lane) at the exact point where the slip road from the A436/B4070 joins is not ideal. Better to extend over the brow of the hill for another half mile or so...
Also, rather amusingly, the video shows that signage for the junction will be obscured by foliage from the outset!
SouthWest Philip wrote: ↑Mon Sep 30, 2019 18:47
The proposed scheme, on the whole, is good but for the negative impact on the A436.
Aside for the increased distance for the not insignificant east-west flow (effectively the Cheltenham bypass for the A40), the proposed junction layout for the A436 introduces a conflict where westbound and eastbound traffic have to cross each other reminiscent of the failed layout at the M40/A43 Cherwell Valley junction.
I have wondered whether it might be possible to retain the existing road up the hill to the Air Balloon as an eastbound off slip? If the bridge option was chosen to retain the current A417 from the Air Balloon towards Birdlip, it might be possible to add a loop from the A436 to A417 for westbound traffic? Other movements could be catered for via the Cowley junction and retaining the old Birdlip bypass.
Fair comment about the A436.
As it is they have an S1 road going along next to the new A417 between Dog Rd and the A436 rbt. I don't see that there is actually much point to this road between Dog Rd and Cold Slad Lane as there are no property accesses on that section. So they could just replace it with an eastbound offslip along the lines you suggest, which becomes two way between Cold Slad Lane and the A436 rbt (NMU access could be provided for the whole length of course).
Combining the bridge option (Alternative 1) with a looped westbound A436 onslip would be a great idea. If you look at the Option 30 alternatives (p. 26 at link below) they don't seem to have considered this, though maybe the vertical alignment is too tricky.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
Can't give gradient ratio, but the documentation suggests through use of cuttings and embankments it will be a longer, more consistent but slightly less steep gradient than the current road.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
Can't give gradient ratio, but the documentation suggests through use of cuttings and embankments it will be a longer, more consistent but slightly less steep gradient than the current road.
Don’t quote me on this, but I think I recall seeing a gradient profile showing a 7% incline in one of the documents.
Edit: it’s in the “Mainline Plan and Profile Sheet” documents.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
Can't give gradient ratio, but the documentation suggests through use of cuttings and embankments it will be a longer, more consistent but slightly less steep gradient than the current road.
Don’t quote me on this, but I think I recall seeing a gradient profile showing a 7% incline in one of the documents.
Edit: it’s in the “Mainline Plan and Profile Sheet” documents.
Thanks - that's quite steep for a modern HQDC/expressway!
Perhaps there should be an escape lane or something on the way down, especially as this is going to be pretty steep over quite a long sustained distance.
I also have a concern with the sight lines of the LILO local junction on the westbound downhill. It seems worryingly short considering the road is NSL, downhill at 7% so reduced braking capability, and the junction leads to what appears to be a tractor business. Slow traffic emerging onto a steep down slope on the inside of a bend... Ouch?
I also agree that we should really be trying to not build new GSJs which immediately have conflicting major flows. This is an issue with roundabout addiction, and thanks to the later era of motorway construction on the M4/M6 we know that roundabout junctions are often a problem with today's traffic levels.
All in all like most modern schemes it's a good design with some great innovation, but with some glaring errors and omissions that might bite later.
You don't necessarily have conflicting major flows at roundabouts. For instance, at a conventional dumbbell or two-bridge roundabout, where there are two heavy turning movements (these being the reverse of each other), the major flows are pathed to avoid each other.
It's only where the junction uses an unconventional design, usually with folded slips, that each of two major flows cross each other at-grade. It actually takes ingenuity to make such a bad junction. See the already infamous example at Stonehaven: https://www.google.co.uk/maps/@56.97573 ... 069067,15z
jackal wrote: ↑Tue Oct 01, 2019 18:56
It's only where the junction uses an unconventional design, usually with folded slips, that each of two major flows cross each other at-grade. It actually takes ingenuity to make such a bad junction...
Whilst I have commented that the situation for the A436 is hardly ideal in these plans, I suspect the flows and conflicts at the new roundabouts will in reality be somewhat balanced out by traffic heading along the quickest - although unsigned route - from Cirencester/Swindon to central Cheltenham via Leckhampton.
SouthWest Philip wrote: ↑Mon Sep 30, 2019 20:19
Can't give gradient ratio, but the documentation suggests through use of cuttings and embankments it will be a longer, more consistent but slightly less steep gradient than the current road.
Don’t quote me on this, but I think I recall seeing a gradient profile showing a 7% incline in one of the documents.
Edit: it’s in the “Mainline Plan and Profile Sheet” documents.
Thanks - that's quite steep for a modern HQDC/expressway!
Perhaps there should be an escape lane or something on the way down, especially as this is going to be pretty steep over quite a long sustained distance.
I noticed today, descending the A2 Jubilee Way to the ferry terminal at Dover, that that road has a signed gradient of five per cent and feels pretty steep for a main route - at seven per cent the A417 is going to be in another category again. I suppose modern trucks and cars can handle it OK, but it will surely be the steepest sustained gradient on an HQDC in the U.K..
BTW I noticed the A2’s escape lane was coned off today - not sure whether that’s temporary or permanent.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
The recommended maximum gradient for euro-routes (ie roads with a "E" number) is 8% on roads designed for 80 km/h, decreasing to 4% on roads designed for 120 km/h traffic.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
The recommended maximum gradient for euro-routes (ie roads with a "E" number) is 8% on roads designed for 80 km/h, decreasing to 4% on roads designed for 120 km/h traffic.
Slightly off topic, but I would have thought that the gradients on the M62 between Junctions 21 and 22 eastbound and between Junctions 25 and 24 westbound would have exceeded 4%; they would surely be closer to 8% in places.
roadtester wrote: ↑Mon Sep 30, 2019 19:53
Does anyone know what the maximum gradient is on the new scheme? The existing road is quite steep.
The recommended maximum gradient for euro-routes (ie roads with a "E" number) is 8% on roads designed for 80 km/h, decreasing to 4% on roads designed for 120 km/h traffic.
Slightly off topic, but I would have thought that the gradients on the M62 between Junctions 21 and 22 eastbound and between Junctions 25 and 24 westbound would have exceeded 4%; they would surely be closer to 8% in places.
I think the operative term there is “in places” - at Jubilee Way A2 and the A417 scheme, we’re talking about long sustained stretches of steep gradients.
