New Lower Thames Crossing

[frediculous_biggs]

I am intrigued to see what changes have been made as a result of the consultation, I wonder if this affects the Tilbury junction, or is related to minor diversions due to ecological issues. The local news had a report about some special woodland being destroyed as part of the construction.

Incidentally, please keep the discussion related to the Lower Thames Crossing and not about road widening/building in general

[thatapanydude]

I would if they might look at building a HS into the road rather than the ALR scheme HE have opted with - I would imagine that it should be under consideration after the recent news coverage.

[jackal]

The consultation is open: https://highwaysengland.citizenspace.co ... tion-2020/

Of particular interest:
Guide to consultation https://highwaysengland.citizenspace.co ... ersion.pdf
General arrangements https://highwaysengland.citizenspace.co ... EMENTS.pdf

From a quick look it's very similar to the previous proposals. A few of the bigger things I picked up (running south to north):

- A2/M2 is still in a C/D arrangement but with revisions including new eastbound link from local roads making the new junction even more spaghettified
- Tilbury junction removed
- A13 junction similar freeflow partial access design to the previous but upgraded to reduce weaving: (1) wb>nb and nb>sb slips reconfigured to remove conflicts between them, and (2) braiding on eastbound A13 (already had it westbound)
- between M25 and A13 southbound now has only two lanes. This removes the ridiculous situation in the previous proposal where lane 1 of the M25 southbound became three lanes of LTC. It also certainly is true as they say that a lot of traffic joins from the A13, Even so I'm sceptical of imbalanced arrangements like this (if there's three lanes' worth of traffic on LTC northbound there's likely to be similar southbound) and it would have been better to further widen the M25 southbound to handle a three lane demerge

Aside from the last point I don't think they can be accused of cutting corners - these are impressive proposals.

[frediculous_biggs]

So the changes are listed here: https://highwaysengland.citizenspace.com/ltc/695f932b/

The main changes seem to be:
* The southern tunnel portal has moved south (avoiding marshes, but now encroaching on woodland)
* The A2/LTC junction now has a connection to Gravesend and a few more slips (did Truvelo design this?!)
* Removal of the Tilbury service area and therefore the Tilbury junction
* Adding a local link to the A13/A1089/LTC behemoth, and the realignment of a load of slips
Removal of one lane southbound on the LTC between the M25 and A13
* Slight move of the LTC/M25 junction to avoid some power lines

Edit: Ahh, beaten to it!

[jackal]

* The A2/LTC junction now has a connection to Gravesend and a few more slips (did Truvelo design this?!)

The man himself would be proud:

(click to expand)

[Glom]

Very nice. Looks like it is still just three levels.

[MotorwayPlannerM21]

That is a glorious tangle of slip roads! Definitely an improvement on the previous design.

[Bryn666]

A step up from their usual efforts but some of those local slip roads - eg the two that hit the elongated roundabout are just conflict and congestion generating from day one.

If this is a strategic road why are farty local links even being considered?

[Truvelo]

The elongated roundabout can be removed by freeflowing the sliproads joining it. A bit more spaghetti won't go amiss.

[Peter Freeman]

… - Tilbury junction removed ...

Good … silly old-fashioned junction design, especially for a service area!

[MotorwayPlannerM21]

I'm a bit skeptical of the M2 only having two lanes going through the junction. It wouldn't be difficult to make it three.

[jackal]

I'm a bit skeptical of the M2 only having two lanes going through the junction. It wouldn't be difficult to make it three.

I guess you mean the eastbound mainline on the image above? It's reduced to two lanes so the LTC can join as a double lane gain. Bear in mind that at that point traffic for the LTC and M2 J1 (A289, A2 Rochester) has exited, so it's only traffic heading to M2 J2 or beyond that is on the mainline. Also it has a hard shoulder and what looks like a hashed down lane, so could be expanded to three or four lanes if necessary.

The M2 is widened to four lanes in both directions through J1 btw.

A step up from their usual efforts but some of those local slip roads - eg the two that hit the elongated roundabout are just conflict and congestion generating from day one.

The layout isn't perfect but there are fewer conflicts than at a regular four arm roundabout as two of the arms are one way. Should be fine as a connection to a little S2 LAR.

If this is a strategic road why are farty local links even being considered?

To maintain access currently provided by the local junction at the same site: https://www.google.co.uk/maps/@51.4080421,0.386463,16z

In fact they've not completely achieved this as eastbound local access to the A289 and A2 Rochester is severed. The new eastbound onslip lands between the inner and outercarriageways so could perhaps split to join each of them, though vertical alignment looks challenging.

[Bryn666]

But why? There are two local junctions either side - upgrade those instead of complicating a strategic junction.

But overall it's not worth losing sleep over. The real test will be preventing this from being swamped by local traffic when it should be for priority freight and services from the Channel Ports to anywhere north and east of London.

[Peter Freeman]

I'm a bit skeptical of the M2 only having two lanes going through the junction. It wouldn't be difficult to make it three.

I guess you mean the eastbound mainline on the image above? It's reduced to two lanes so the LTC can join as a double lane gain.

Merging design isn't usually that conservative, and it doesn't need to be here. 3+2=4 is normally quite realistic. I can't see that M2 hatching being rubbed out for many-a-year, so why not do it now?

[Keiji]

I'm just happy that for once, when the 2 lanes leave at the start of that section, the road actually splits properly, 4 into 2+2, without some unnecessary tiger tail. Never could see why they used them when you have multiple lane gains/drops without any reduction in total lane count.

[Peter Freeman]

I'm just happy that for once, when the 2 lanes leave at the start of that section, the road actually splits properly, 4 into 2+2, without some unnecessary tiger tail. Never could see why they used them when you have multiple lane gains/drops without any reduction in total lane count.

Yes. But there is an unnecessary tiger tail at the eastern end's 2+2=4 merge! Presumably ready for if/when they do erase that through-route hatching.

[jackal]

I'm a bit skeptical of the M2 only having two lanes going through the junction. It wouldn't be difficult to make it three.

I guess you mean the eastbound mainline on the image above? It's reduced to two lanes so the LTC can join as a double lane gain.

Merging design isn't usually that conservative, and it doesn't need to be here. 3+2=4 is normally quite realistic. I can't see that M2 hatching being rubbed out for many-a-year, so why not do it now?

If there is a roughly even split of traffic then a double lane gain will increase capacity and safety as you're not funnelling two lanes into one.

Bear in mind the A2/M2 effectively has four lanes through the junction across two carriageways. Five could well be overkill. Indeed I'd query whether the third (or fifth) lane westbound is necessary, as without it the merge could also be handled with lane gains.

Regarding the designation of the road, it looks like the innercarriageway will have to be under motorway conditions as it leads inevitably to the M2. I'm still hesitant to call the innercarriageway through the junction M2 as it could be that designation is used for the LTC via a TOTSO. Hence why I hedge bets calling it A2/M2. The outercarriageway will probably be AP (numbered A2 if the inner is M2).

[Peter Freeman]

I guess you mean the eastbound mainline on the image above? It's reduced to two lanes so the LTC can join as a double lane gain.

Merging design isn't usually that conservative, and it doesn't need to be here. 3+2=4 is normally quite realistic. I can't see that M2 hatching being rubbed out for many-a-year, so why not do it now?

If there is a roughly even split of traffic then a double lane gain will increase capacity and safety as you're not funnelling two lanes into one.

Agreed.

Bear in mind the A2/M2 effectively has four lanes through the junction across two carriageways.

But despite the M2 eastbound splitting equally (4=2+2) at the west side, I suspect that the inner carriageway (M2 eastbound) will carry more traffic than the outer one (A2 eastbound), since that seems to be the case now according to current lane allocations. The hatching shows that the designers half agree.

Five could well be overkill.

Overkill is no problem, especially when you've already laid the black-top.

Indeed I'd query whether the third (or fifth) lane westbound is necessary, as without it the merge could also be handled with lane gains.

Yes, why 3 M2 lanes westbound if only 2 eastbound? Especially since that 3-lane section grows spontaneously out of a 2-lane section. It's future-proofing again. I suppose I should be happy.

Anyway, having niggled over all that, it is actually a pretty good design.

[Nathan_A_RF]

Is there really still nothing being done to the A229 Bluebell Hill? With the scheme going through these amendments I'd have thought something would have been brought up about the amount of Channel traffic flowing through the roundabouts at M2 J3 and twisting downward dual carriageway to the M20.

[ChrisH]

Is there really still nothing being done to the A229 Bluebell Hill? With the scheme going through these amendments I'd have thought something would have been brought up about the amount of Channel traffic flowing through the roundabouts at M2 J3 and twisting downward dual carriageway to the M20.

Indeed the modelling report suggests over 1000 vehicles per hour extra on the A229. I suspect we'll have to let it settle and then wait for DfT and HE to realise something needs to be done...