Gatwick Airport's Highway improvements (A23/M23/A217)

[Peter Freeman]

^ Yes, same problem, same solution. Similarly at M6J15, which I assume was also un-signalised in its early life. I'm sure those roundabouts will, at times, still queue back to the merge, but nevertheless, the weaving problem is solved, because lane selection occurs when joining the queue, not while in it.

The important point, which might not be obvious to all, is that this modification doesn't simply make the driving easier and safer, but actually increases the throughput and protects the motorway mainline.

[Bryn666]

^ Yes, same problem, same solution. Similarly at M6J15, which I assume was also un-signalised in its early life. I'm sure those roundabouts will, at times, still queue back to the merge, but nevertheless, the weaving problem is solved, because lane selection occurs when joining the queue, not while in it.

The important point, which might not be obvious to all, is that this modification doesn't simply make the driving easier and safer, but actually increases the throughput and protects the motorway mainline.

Exactly this, although there are some new build examples which should never have been designed that way from the off - the John Smeaton Viaduct in Leeds springs to mind. It's almost a fetish in Leeds to put signals on everything, the bigger and more sprawling (and thus less efficient with all the additional streams) the better it seems.

[jackal]

The consultation opened today. The road plans are similar to the previous ones, with a two-bridge roundabout GSJ replacing the south terminal roundabout and various bits of widening. The main changes are at the north terminal junction, which has been somewhat simplified. The current Airport Way bridge over the A23 has been changed to westbound running only, allowing the proposed flyover onto the A23 northbound to be significantly shorter and a continuation of the mainline rather than a diverge to the left. They're also now proposing to retain the north terminal roundabout, though it will be signalised and enlarged.

It's not really bad overall, but there are a few areas for improvement:

- The loop for A23 northbound towards Airport Way has been removed, so this now requires a U-turn at the roundabout and right turn at the signalised T. The heavy movement from the airport to Airport Way also now goes through that T-junction as Airport Way is westbound only over the A23. Given this, I think they could do more to let traffic bypass the T-junction, with a freeflow left turn for traffic from the airport heading to A23 northbound, and a freeflow bypass lane for A23 southbound to Airport Way. The latter would replace the big tigertail on the southbound A23.
- The main route out of the airport (Northway) should actually be freeflow as far as the A23 via segregation from the main roundabout, just like that for the main route into the airport. There would be a LILO on that segregated section for Longbridge Way, just like that which Gatwick Way has on the other side of the roundabout. Longbridge Way doesn't access to the roundabout proper as it can access the North terminal via the Northgate tunnel and Gatwick Way, and the A23 northbound can reach Longbridge Way via the North Perimeter Road.
- As previously speculated, the M23 spur would be reclassified as an A road, which is a retrograde step.

https://www.gatwickairport.com/business ... rn-runway/

[SouthWest Philip]

Let's hope they're not the final designs for the signs. Just about every one is botched in some way or other.

The spur should probably get it's own number too. A2323 maybe? Although I guess it could be an extension of the A217.

[jervi]

The consultation opened today. The road plans are similar to the previous ones, with a two-bridge roundabout GSJ replacing the south terminal roundabout and various bits of widening. The main changes are at the north terminal junction, which has been somewhat simplified. The current Airport Way bridge over the A23 has been changed to westbound running only, allowing the proposed flyover onto the A23 northbound to be significantly shorter and a continuation of the mainline rather than a diverge to the left. They're also now proposing to retain the north terminal roundabout, though it will be signalised and enlarged.


Gatwick 2022 - Copy.JPG


It's not really bad overall, but there are a few areas for improvement:

- The loop for A23 northbound towards Airport Way has been removed, so this now requires a U-turn at the roundabout and right turn at the signalised T. The heavy movement from the airport to Airport Way also now goes through that T-junction as Airport Way is westbound only over the A23. Given this, I think they could do more to let traffic bypass the T-junction, with a freeflow left turn for traffic from the airport heading to A23 northbound, and a freeflow bypass lane for A23 southbound to Airport Way. The latter would replace the big tigertail on the southbound A23.
- The main route out of the airport (Northway) should actually be freeflow as far as the A23 via segregation from the main roundabout, just like that for the main route into the airport. There would be a LILO on that segregated section for Longbridge Way, just like that which Gatwick Way has on the other side of the roundabout. Longbridge Way doesn't access to the roundabout proper as it can access the North terminal via the Northgate tunnel and Gatwick Way, and the A23 northbound can reach Longbridge Way via the North Perimeter Road.
- As previously speculated, the M23 spur would be reclassified as an A road, which is a retrograde step.

https://www.gatwickairport.com/business ... rn-runway/

... I had the consultation opening on the 16th it in my calendar. What are they actually going to achieve by making the spur not a motorway? It only leads to a motorway *facepalm*. Also I hope who ever creates the signs for this does not look at the examples in this document, there is only 2 without any errors on out of the 15.
In terms of the spur numbering, it would probably just become a spur of the A23, it will not need its own number.

Also looks like they have dropped the proposed changes at Queens gate. Shame they still haven't provided any details on what NMU improvements they are going to make other than the measly link to Longbridge Roundabout.

[Bryn666]

The consultation opened today. The road plans are similar to the previous ones, with a two-bridge roundabout GSJ replacing the south terminal roundabout and various bits of widening. The main changes are at the north terminal junction, which has been somewhat simplified. The current Airport Way bridge over the A23 has been changed to westbound running only, allowing the proposed flyover onto the A23 northbound to be significantly shorter and a continuation of the mainline rather than a diverge to the left. They're also now proposing to retain the north terminal roundabout, though it will be signalised and enlarged.


Gatwick 2022 - Copy.JPG


It's not really bad overall, but there are a few areas for improvement:

- The loop for A23 northbound towards Airport Way has been removed, so this now requires a U-turn at the roundabout and right turn at the signalised T. The heavy movement from the airport to Airport Way also now goes through that T-junction as Airport Way is westbound only over the A23. Given this, I think they could do more to let traffic bypass the T-junction, with a freeflow left turn for traffic from the airport heading to A23 northbound, and a freeflow bypass lane for A23 southbound to Airport Way. The latter would replace the big tigertail on the southbound A23.
- The main route out of the airport (Northway) should actually be freeflow as far as the A23 via segregation from the main roundabout, just like that for the main route into the airport. There would be a LILO on that segregated section for Longbridge Way, just like that which Gatwick Way has on the other side of the roundabout. Longbridge Way doesn't access to the roundabout proper as it can access the North terminal via the Northgate tunnel and Gatwick Way, and the A23 northbound can reach Longbridge Way via the North Perimeter Road.
- As previously speculated, the M23 spur would be reclassified as an A road, which is a retrograde step.

https://www.gatwickairport.com/business ... rn-runway/

WTF are those signs. Apparently further in the document it says "illustrative only" so hopefully sense will prevail there.

Pity another length of motorway is being eradicated for no reason other than presumably NH wants rid of maintenance rights.

[jackal]

A slip from A23 northbound to the flyover would remove the conflicts at the T-junction. The diverge to Airport Way is close, and a signalised merge onto the A23 southbound may or may not be needed. But even if it was, the timings would much much more favourable with A23 northbound traffic bypassing the lights altogether.

[Phil]

What are they actually going to achieve by making the spur not a motorway? It only leads to a motorway *facepalm*.

No accusations they are creating more ‘Smart motorways’ (and technically removing a short length too) is my suspicion.

Also there are an awful lot of A roads that end on a motorway and require non-motorway traffic to double back - M40 junction 14 and the A6144 spur to the M60 being two examples while I have a suspicion that J3 of the M18 was a similar dead end for decades before the A6182 got extended.

[Phil]

A slip from A23 northbound to the flyover would remove the conflicts at the T-junction. The diverge to Airport Way is close, and a signalised merge onto the A23 southbound may or may not be needed. But even if it was, the timings would much much more favourable with A23 northbound traffic bypassing the lights altogether.


Gatwick 2022 revised - Copy.jpg

As good as that might be I’m not sure traffic volumes N/S along the A23 justify it.

However due to the lack of intermediate junctions on the M23 there is significant non- airport traffic flows between the M23 spur and the A23 / A217 roads and that is probably the main reason the northbound spur - northbound free flow has been proposed so as to avoid clogging up the North Terminal roundabout with non-airport traffic

[jervi]

What are they actually going to achieve by making the spur not a motorway? It only leads to a motorway *facepalm*.

No accusations they are creating more ‘Smart motorways’ (and technically removing a short length too) is my suspicion.

Also there are an awful lot of A roads that end on a motorway and require non-motorway traffic to double back - M40 junction 14 and the A6144 spur to the M60 being two examples while I have a suspicion that J3 of the M18 was a similar dead end for decades before the A6182 got extended.

If my memory serves me right, if the Northern runway scheme is approved in 2023, the Highway works are programmed in for 2029-2032 - I imagine all this smart motorway ban would of all expired and blown over by then so don't think that would be the sole reason.

Its probably just legally easier to remove the motorway status of the spur, than it is to modify the existing orders to cover the new fly over or some bs like that. Or are they going to try and open up the Eastern side of J9 for development?

Or maybe they are removing the motorway status from it due to lane widths which would happen on the spur if EB was widened to 3 lanes, so it wouldn't conform to standards. But like if that is the case why not remove motorway status from the roads connecting the M25 & M23.

[Chris5156]

Its probably just legally easier to remove the motorway status of the spur, than it is to modify the existing orders to cover the new fly over or some bs like that. Or are they going to try and open up the Eastern side of J9 for development?

It wouldn’t be the first time a motorway terminal roundabout has been grade separated and the motorway has been cut back rather than extended through the junction. I do wonder whether to some extent this stuff is related to a lack of experience with the legal side of motorways within the highways industry, since there can’t be many people with real-world experience of creating or amending motorways any more. If you don’t build motorways you’ll eventually lose the institutional memory of how to do it.

[Phil]

What are they actually going to achieve by making the spur not a motorway? It only leads to a motorway *facepalm*.

No accusations they are creating more ‘Smart motorways’ (and technically removing a short length too) is my suspicion.

Also there are an awful lot of A roads that end on a motorway and require non-motorway traffic to double back - M40 junction 14 and the A6144 spur to the M60 being two examples while I have a suspicion that J3 of the M18 was a similar dead end for decades before the A6182 got extended.

If my memory serves me right, if the Northern runway scheme is approved in 2023, the Highway works are programmed in for 2029-2032 - I imagine all this smart motorway ban would of all expired and blown over by then so don't think that would be the sole reason.

Its probably just legally easier to remove the motorway status of the spur, than it is to modify the existing orders to cover the new fly over or some bs like that. Or are they going to try and open up the Eastern side of J9 for development?

Or maybe they are removing the motorway status from it due to lane widths which would happen on the spur if EB was widened to 3 lanes, so it wouldn't conform to standards. But like if that is the case why not remove motorway status from the roads connecting the M25 & M23.

Although its unlikely - its possible that the current review into smart motorways might well limit or put conditions on their use. As such its a lot easier to plan the scheme as a bog standard A road rather than end up with some smart arse legal bod getting the whole scheme delayed / put on hold because an apparent conflict with the new smart motorway guidance.

While I would normally agree that 'facilitating development' might be a contributing factor, I don't think the land surrounding Junc 9 is suitable for such a development and any such development is more likely to be off the airport junction instead (as per Reigate & Banstead BC plan)

[Phil]

Its probably just legally easier to remove the motorway status of the spur, than it is to modify the existing orders to cover the new fly over or some bs like that. Or are they going to try and open up the Eastern side of J9 for development?

It wouldn’t be the first time a motorway terminal roundabout has been grade separated and the motorway has been cut back rather than extended through the junction. I do wonder whether to some extent this stuff is related to a lack of experience with the legal side of motorways within the highways industry, since there can’t be many people with real-world experience of creating or amending motorways any more. If you don’t build motorways you’ll eventually lose the institutional memory of how to do it.

Or Parliamentary / Governmental time?

Its pretty well known that attempts to re-designate the rebuilt A14 between Huntingdon and Cambridge failed because of the Brexit induced logjam in the Whitehall machine meaning the opening would have to have been significantly delayed (opening it as all purpose and trying to rescind that status is even more difficult in the long run as it means stopping up a public right of way).

[jackal]

The DCO application for the Northern Runway has been accepted for examination. The highways plans seem to be basically the same as those that were consulted on last summer, so I'll lazily repeat my comments:

The consultation opened today. The road plans are similar to the previous ones, with a two-bridge roundabout GSJ replacing the south terminal roundabout and various bits of widening. The main changes are at the north terminal junction, which has been somewhat simplified. The current Airport Way bridge over the A23 has been changed to westbound running only, allowing the proposed flyover onto the A23 northbound to be significantly shorter and a continuation of the mainline rather than a diverge to the left. They're also now proposing to retain the north terminal roundabout, though it will be signalised and enlarged.

Gatwick 2022 - Copy.JPG

It's not really bad overall, but there are a few areas for improvement:

- The loop for A23 northbound towards Airport Way has been removed, so this now requires a U-turn at the roundabout and right turn at the signalised T. The heavy movement from the airport to Airport Way also now goes through that T-junction as Airport Way is westbound only over the A23. Given this, I think they could do more to let traffic bypass the T-junction, with a freeflow left turn for traffic from the airport heading to A23 northbound, and a freeflow bypass lane for A23 southbound to Airport Way. The latter would replace the big tigertail on the southbound A23.
- The main route out of the airport (Northway) should actually be freeflow as far as the A23 via segregation from the main roundabout, just like that for the main route into the airport. There would be a LILO on that segregated section for Longbridge Way, just like that which Gatwick Way has on the other side of the roundabout. Longbridge Way doesn't access to the roundabout proper as it can access the North terminal via the Northgate tunnel and Gatwick Way, and the A23 northbound can reach Longbridge Way via the North Perimeter Road.
- As previously speculated, the M23 spur would be reclassified as an A road, which is a retrograde step.

https://www.gatwickairport.com/business ... rn-runway/

My only new complaint is with the idiotic removal of the segregated left-turn onto the M23.

General arrangements: https://infrastructure.planninginspecto ... proval.pdf
Structure section drawings (includes some lane allocations): https://infrastructure.planninginspecto ... proval.pdf
DCO documents: https://national-infrastructure-consent ... PerPage=25

[Phil]

My only new complaint is with the idiotic removal of the segregated left-turn onto the M23.

Its not that idiotic - given its poor alignment. Of course if it had been done properly as a constant curve which gently flows round the corner on a nice gentle curve it might be a different story...

* for those that don't know the left hand lane which makes the free flow turn is the old hard shoulder - but the roundabout at Junc 9 was built without them so on final approach all three lanes kink right before the 'free flow' lane veers sharply to the left hugging the outer edge of the roundabout while the other two lanes now have a substandard entry onto the bodged roundabout (which has been widened only slightly.

Compare https://www.google.com/maps/@51.1595581 ... ?entry=ttu
and https://www.google.com/maps/@51.1596012 ... ?entry=ttu

[jackal]

Given the increase in upstream capacity (widening the spur to three lanes eastbound and GSJing the south terminal roundabout) it just seems regressive to remove what freeflow there is at J9. It should be the give way line that goes via conversion to a teardrop.

[jervi]

They still planning on removing motorway regulations from the spur... How pointless & stupid, if anything the whole spur should now be under motorway regulations since South terminal would be GSJ'd.
Not sure if it was like it before, but the South Terminal flyover seems to have very wide verges, enough for an additional 3rd lane if they like.

All in all, very underwhelming the proposed changes.

[Bryn666]

Given the increase in upstream capacity (widening the spur to three lanes eastbound and GSJing the south terminal roundabout) it just seems regressive to remove what freeflow there is at J9. It should be the give way line that goes via conversion to a teardrop.

The DMRB wonks won't like that because the entry geometry into the former roundabout isn't going to be a Monza style banked curve and therefore will be verboten.

The days of pulling tricks like M4 J19 are gone - it's either designed to be ridiculously over engineered and therefore discounted as impossible to justify so it'll end up as a signalised roundabout at best when all obvious logic says this should have been a trumpet from the start.

[SteveA30]

If the spur loses its motorway regulations, will that allow developers to move in via a new rbt between M23 and the new GSJ? The land between M23 and the railway is undeveloped. Thus, a rbt turned into a GSJ will be ruined by a new rbt or complex signalised crossroads close by. Just saying....

[jackal]

I believe Gatwick plan to have a development off the north side of the new GSJ.