New Lower Thames Crossing

The study of British and Irish roads - their construction, numbering, history, mapping, past and future official roads proposals and general roads musings.

There is a separate forum for Street Furniture (traffic lights, street lights, road signs etc).

Registered users get access to other forums including discussions about other forms of transport, driving, fantasy roads and wishlists, and roads quizzes.

Moderator: Site Management Team

Post Reply
User avatar
ChrisH
Elected Committee Member
Posts: 3975
Joined: Wed Nov 13, 2002 11:29

Re: New Lower Thames Crossing

Post by ChrisH »

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.
User avatar
Ritchie333
Assistant Site Manager
Posts: 11765
Joined: Tue May 20, 2003 20:40
Location: Ashford, Kent
Contact:

Re: New Lower Thames Crossing

Post by Ritchie333 »

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.
--
SABRE Maps - all the best maps in one place....
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

Here's an alternative freeflow design:
A13 A1089 - Copy.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.
85CF380
Member
Posts: 326
Joined: Sat Jun 29, 2013 18:51
Location: W Yorks

Re: New Lower Thames Crossing

Post by 85CF380 »

jackal wrote:Here's an alternative freeflow design:
see above - That looks twice as good as their version & I agree
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.
User avatar
Chris5156
Deputy Treasurer
Posts: 16908
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: New Lower Thames Crossing

Post by Chris5156 »

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.
jackal wrote:Here's an alternative freeflow design:
(snip)
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.
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

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.
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).
jackal wrote:Here's an alternative freeflow design:
(snip)
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.
Whoops! Will upload corrected version later.
User avatar
Truvelo
Member
Posts: 17467
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: New Lower Thames Crossing

Post by Truvelo »

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.
Attachments
a13.jpg
Last edited by Truvelo on Fri Nov 24, 2017 10:27, edited 1 time in total.
How would you like your grade separations, Sir?
Big and complex.
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

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.
darkcape
Member
Posts: 2094
Joined: Wed Aug 29, 2012 14:54

Re: New Lower Thames Crossing

Post by darkcape »

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)
Did you know there's more to SABRE than just the Forums?
Add your roads knowledge to the SABRE Wiki today!
Have you browsed SABRE Maps recently? Try getting involved!
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

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)
When it's the key junction in a £6bn project? Not really.
ais523
Member
Posts: 1139
Joined: Tue Sep 08, 2015 19:52
Location: Birmingham

Re: New Lower Thames Crossing

Post by ais523 »

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.)
Glom
Member
Posts: 2827
Joined: Wed Jan 12, 2011 17:05
Location: Wiltshire

Re: New Lower Thames Crossing

Post by Glom »

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.)
Maybe it's a feature like on the Rainbow Bridge in Tokyo.
User avatar
Truvelo
Member
Posts: 17467
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: New Lower Thames Crossing

Post by Truvelo »

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.
I've added that movement. As you say, the limitations of the original drawing may be the reason for its omission.
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.)
Yes, the new roundabout it leads to is clearly higher. I can't see any other way of gaining that height.
How would you like your grade separations, Sir?
Big and complex.
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

With that slip and a slip for wb>nb (in blue below) it starts to look like a more sensible design:
Truvelo A13 A1089 revised - Copy.jpg
I think the levels of the roundabout, LTC, A1013, A1089 and loop are rather ambiguous, though inessential to understanding the horizontal geometry.
User avatar
jackal
Member
Posts: 7549
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: New Lower Thames Crossing

Post by jackal »

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
User avatar
Truvelo
Member
Posts: 17467
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: New Lower Thames Crossing

Post by Truvelo »

You need to submit it to HE :D
How would you like your grade separations, Sir?
Big and complex.
A9NWIL
Member
Posts: 3319
Joined: Fri Jul 01, 2016 02:36

Re: New Lower Thames Crossing

Post by A9NWIL »

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
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.
Formerly known as 'lortjw'
User avatar
Patrick Harper
Member
Posts: 3202
Joined: Sat Jan 16, 2010 14:41
Location: Wiltshire

Re: New Lower Thames Crossing

Post by Patrick Harper »

Two years ago I attempted a southern terminus design assuming an M2/A289 rebuild, and this was the result:

Image

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.
User avatar
MotorwayPlannerM21
Member
Posts: 362
Joined: Sun Mar 12, 2017 19:08
Location: vaguely near London
Contact:

Re: New Lower Thames Crossing

Post by MotorwayPlannerM21 »

Paianni wrote:Two years ago I attempted a southern terminus design assuming an M2/A289 rebuild, and this was the result:

Image

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.
How would there be access to the A2 into Medway?
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.
"All roads lead to Rome"
What about the M25?

The A205 - The road to... oh wait I should've turned right back there!
ais523
Member
Posts: 1139
Joined: Tue Sep 08, 2015 19:52
Location: Birmingham

Re: New Lower Thames Crossing

Post by ais523 »

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 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.
Post Reply