New Lower Thames Crossing
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Re: New Lower Thames Crossing
That A13 junction is an abomination. I suppose that with the new access to Tilbury from the east, the A1089 could be detrunked and hence the more local nature of that roundabout?
Even so, it would be far better to have free flow at least between all directions of A13 and LTC.
Even so, it would be far better to have free flow at least between all directions of A13 and LTC.
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Re: New Lower Thames Crossing
What I don’t get from that junction design is where they think most of the traffic is going to go. Presumably this crossing is going to mostly benefit those going around the Kent / Essex coastline, while anyone further inland will continue to use Dartford.
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Re: New Lower Thames Crossing
Here's an alternative freeflow design:
(Apologies for image quality - the png was too big so I had to use jpg.)
(Apologies for image quality - the png was too big so I had to use jpg.)
Last edited by jackal on Thu Nov 23, 2017 20:30, edited 3 times in total.
Re: New Lower Thames Crossing
see above - That looks twice as good as their version & I agreejackal wrote:Here's an alternative freeflow design:
.ChrisH wrote:That (official) A13 junction is an abomination
Still surprised the A13 eastbound, being only 3 junctions from the M25 will generate enough traffic for mid & east Kent to justify free-flow.
Re: New Lower Thames Crossing
The revised A13 junction diagram seems very vague - not all the sliproads actually join and it's not clear where the mainlines run. It certainly takes some picking apart.
I wonder whether the existing slip from the A13 westbound towards Tilbury, and the existing from the A13 eastbound around the north of the loop towards Tilbury, are meant to be retained. The new design doesn't label them but it includes nothing that would conflict with them, and indeed the new exit from the southbound Crossing approach towards Tilbury deliberately loops around to join the A13 westbound off-slip. I'm willing to believe at this stage that it might just be a bad drawing of a passable design.
I wonder whether the existing slip from the A13 westbound towards Tilbury, and the existing from the A13 eastbound around the north of the loop towards Tilbury, are meant to be retained. The new design doesn't label them but it includes nothing that would conflict with them, and indeed the new exit from the southbound Crossing approach towards Tilbury deliberately loops around to join the A13 westbound off-slip. I'm willing to believe at this stage that it might just be a bad drawing of a passable design.
I like this a lot. I think you need a slip from the new crossing towards the A13 westbound but I think we can take that as read. The rest is very sensible.jackal wrote:Here's an alternative freeflow design:
(snip)
Chris
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Re: New Lower Thames Crossing
Pretty sure the mainline goes through the middle, between the loops. Otherwise there is no way for the northbound mainline to be provided. I'm also pretty sure those movements you mentioned aren't included. Wb>sb conflicts with the braiding merge point, while eb>sb cuts across the nb mainline (also it's provided already via the rbt).Chris5156 wrote:The revised A13 junction diagram seems very vague - not all the sliproads actually join and it's not clear where the mainlines run. It certainly takes some picking apart.
I wonder whether the existing slip from the A13 westbound towards Tilbury, and the existing from the A13 eastbound around the north of the loop towards Tilbury, are meant to be retained. The new design doesn't label them but it includes nothing that would conflict with them, and indeed the new exit from the southbound Crossing approach towards Tilbury deliberately loops around to join the A13 westbound off-slip. I'm willing to believe at this stage that it might just be a bad drawing of a passable design.
Whoops! Will upload corrected version later.I like this a lot. I think you need a slip from the new crossing towards the A13 westbound but I think we can take that as read. The rest is very sensible.jackal wrote:Here's an alternative freeflow design:
(snip)
Re: New Lower Thames Crossing
I've redrawn the junction to make it clearer.
What's immediately obvious is the intention to use as much of the existing trumpet as possible. If that's the case then D2 is the best that can be achieved through the existing bridge under the A13.
There are a couple of things I'm not keen on. A is a right hand exit which can't easily be solved without realigning the underpass beneath the roundabout. B is an unnecessary bridge which could be avoided if the A13 westbound exit slip merged to the left instead of passing beneath the A13 eastbound slip. My only reasoning behind this additional bridge is it increase the radii of the curved slip.
Speaking of curves the new roundabout on the A1089 mainline must be substantially higher than the new road if the southbound exit slip has to loop back on itself to gain height instead of being straight.
What's immediately obvious is the intention to use as much of the existing trumpet as possible. If that's the case then D2 is the best that can be achieved through the existing bridge under the A13.
There are a couple of things I'm not keen on. A is a right hand exit which can't easily be solved without realigning the underpass beneath the roundabout. B is an unnecessary bridge which could be avoided if the A13 westbound exit slip merged to the left instead of passing beneath the A13 eastbound slip. My only reasoning behind this additional bridge is it increase the radii of the curved slip.
Speaking of curves the new roundabout on the A1089 mainline must be substantially higher than the new road if the southbound exit slip has to loop back on itself to gain height instead of being straight.
Last edited by Truvelo on Fri Nov 24, 2017 10:27, edited 1 time in total.
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Re: New Lower Thames Crossing
Yes, that's exactly how I read the drawing. The only thing that I think might be different in the actual plan is there may be a slip for A1089>A13wb in the centre of the interchange. There's no reason for it not to be there, and it's a pretty important movement (docks>London). The drawing leaves out several diverge/merge points, and for this slip the diverge and merge would be close enough together that the whole slip may have been omitted.
Re: New Lower Thames Crossing
The first design I counted 19 bridges and the revised version 11 - Don't be surprised if it gets watered down even more. 11 new bridges for one junction is madness (from a cost perspective)
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Re: New Lower Thames Crossing
When it's the key junction in a £6bn project? Not really.darkcape wrote:The first design I counted 19 bridges and the revised version 11 - Don't be surprised if it gets watered down even more. 11 new bridges for one junction is madness (from a cost perspective)
Re: New Lower Thames Crossing
What's up with the 360° loop? I assume it's something to do with vertical elevation, as there's no other plausible reason I'm aware of for something like that. (Are there any in existing junctions? I can't think of any.)
As for the whole "roundabout to A13 west" issue, is there enough room in the centre there for a slip while maintaining standards? There's no weaving problems – you'd be adding a merge before another merge – but the actual amount of space there for a 3-into-1 merge is fairly short, and there are limits on consecutive merges to avoid that sort of problem. (Knowing how many lanes each sliproad is, and where lane drops/gains are, would help.)
As for the whole "roundabout to A13 west" issue, is there enough room in the centre there for a slip while maintaining standards? There's no weaving problems – you'd be adding a merge before another merge – but the actual amount of space there for a 3-into-1 merge is fairly short, and there are limits on consecutive merges to avoid that sort of problem. (Knowing how many lanes each sliproad is, and where lane drops/gains are, would help.)
Re: New Lower Thames Crossing
Maybe it's a feature like on the Rainbow Bridge in Tokyo.ais523 wrote:What's up with the 360° loop? I assume it's something to do with vertical elevation, as there's no other plausible reason I'm aware of for something like that. (Are there any in existing junctions? I can't think of any.)
As for the whole "roundabout to A13 west" issue, is there enough room in the centre there for a slip while maintaining standards? There's no weaving problems – you'd be adding a merge before another merge – but the actual amount of space there for a 3-into-1 merge is fairly short, and there are limits on consecutive merges to avoid that sort of problem. (Knowing how many lanes each sliproad is, and where lane drops/gains are, would help.)
Re: New Lower Thames Crossing
I've added that movement. As you say, the limitations of the original drawing may be the reason for its omission.jackal wrote:Yes, that's exactly how I read the drawing. The only thing that I think might be different in the actual plan is there may be a slip for A1089>A13wb in the centre of the interchange. There's no reason for it not to be there, and it's a pretty important movement (docks>London). The drawing leaves out several diverge/merge points, and for this slip the diverge and merge would be close enough together that the whole slip may have been omitted.
Yes, the new roundabout it leads to is clearly higher. I can't see any other way of gaining that height.ais523 wrote:What's up with the 360° loop? I assume it's something to do with vertical elevation, as there's no other plausible reason I'm aware of for something like that. (Are there any in existing junctions? I can't think of any.)
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Re: New Lower Thames Crossing
With that slip and a slip for wb>nb (in blue below) it starts to look like a more sensible design:
I think the levels of the roundabout, LTC, A1013, A1089 and loop are rather ambiguous, though inessential to understanding the horizontal geometry.
I think the levels of the roundabout, LTC, A1013, A1089 and loop are rather ambiguous, though inessential to understanding the horizontal geometry.
Re: New Lower Thames Crossing
I had a go at making the HE design freeflow. I think it worked out surprisingly well. I saved five bridges by removing the massive A13eb to LTCsb slip. There are some new bridges but the overall amount of structural content should be about the same. The main changes in connectivity are:
+ Added A13wb to LTCnb
- Removed links to A1013 (its existing bridge over the A1089 is retained)
+ Added A13wb to LTCnb
- Removed links to A1013 (its existing bridge over the A1089 is retained)
Re: New Lower Thames Crossing
You need to submit it to HE
How would you like your grade separations, Sir?
Big and complex.
Big and complex.
Re: New Lower Thames Crossing
Very good I didnt understand HE's idea of trying to join the A1013 into the mix and it makes sense to have the A1089 stay as is, but you have gone one better with it linking to the new LTC nb.jackal wrote:I had a go at making the HE design freeflow. I think it worked out surprisingly well. I saved five bridges by removing the massive A13eb to LTCsb slip. There are some new bridges but the overall amount of structural content should be about the same. The main changes in connectivity are:
+ Added A13wb to LTCnb
- Removed links to A1013 (its existing bridge over the A1089 is retained)
Truvelo A13 A1089 freeflow - Copy.jpg
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- Patrick Harper
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Re: New Lower Thames Crossing
Two years ago I attempted a southern terminus design assuming an M2/A289 rebuild, and this was the result:
This example involves a TOTSO, though in hindsight there are easy ways to remove some of it, for instance flaring the N/S mainline carriageway to create space for an M2E->M2S sliproad occupying the NW corner of the interchange. In order for this sort of design to work, the larger project would have to be rethought as the predominating trunk route from the M20 to Essex - The M2 alignment south of Toddington Wood would be rerouted parallel to HS1 (new junction for old M2, and A289 access moved to a spur to M20 J6 to prevent weaving) and merge into the M20 around Detling. Whether this could be afforded at this point, I have no idea.
This example involves a TOTSO, though in hindsight there are easy ways to remove some of it, for instance flaring the N/S mainline carriageway to create space for an M2E->M2S sliproad occupying the NW corner of the interchange. In order for this sort of design to work, the larger project would have to be rethought as the predominating trunk route from the M20 to Essex - The M2 alignment south of Toddington Wood would be rerouted parallel to HS1 (new junction for old M2, and A289 access moved to a spur to M20 J6 to prevent weaving) and merge into the M20 around Detling. Whether this could be afforded at this point, I have no idea.
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Re: New Lower Thames Crossing
How would there be access to the A2 into Medway?Paianni wrote:Two years ago I attempted a southern terminus design assuming an M2/A289 rebuild, and this was the result:
This example involves a TOTSO, though in hindsight there are easy ways to remove some of it, for instance flaring the N/S mainline carriageway to create space for an M2E->M2S sliproad occupying the NW corner of the interchange. In order for this sort of design to work, the larger project would have to be rethought as the predominating trunk route from the M20 to Essex - The M2 alignment south of Toddington Wood would be rerouted parallel to HS1 (new junction for old M2, and A289 access moved to a spur to M20 J6 to prevent weaving) and merge into the M20 around Detling. Whether this could be afforded at this point, I have no idea.
This is quite important but your design seems to get rid of it.
I would suggest building a new A2 to the Gravesend turnoff, so access would be from there. The junction at Cobham would be removed so there would also be an access road to M2 J2 for access to the M2 and A228.
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Re: New Lower Thames Crossing
The places where a slip road leaves one road and almost immediately merges into another look scary (especially the southbound one, where the merge happens on a 360° curve!). In practice, you'd almost certainly need to lay that out as a lane drop + lane gain for safety reasons, which means that some of the roads will have to be built with extra lanes. You're also going to have trouble fitting everything in vertically with that sort of density of bridges near the centre of the junction. Still, it may be that the topology works out and all that needs changing is the geometry.jackal wrote:I had a go at making the HE design freeflow. I think it worked out surprisingly well. I saved five bridges by removing the massive A13eb to LTCsb slip. There are some new bridges but the overall amount of structural content should be about the same.