Brussels Ring Road Improvements: Werken aan de Ring

[jackal]

There is a major project on the Brussels ring road R0 called Werken aan de Ring (the translation is what it sounds like).

Most of the big changes are on Ring North. Here is a quick summary of this area, focusing on system interchanges, running clockwise from Groot Bijgaarden (E40) in the west.

Zone 1: From Groot-Bijgaarden to Meise: https://www.werkenaandering.be/en/zone-1

E40 Groot-Bijgaarden - stack turbine replaced with four level stack. Braiding added on north side to better utilise existing C/D lanes.
A12 Strombeek-Bever - stacked roundabout replaced with four level stack

Vilvoorde Zone 2: From Grimbergen to Vilvoorde: https://www.werkenaandering.be/en/zone-2

The main element here is renovation of the long Vilvoorde viaduct and eventual addition of a fourth lane.

Zone 3: From Machelen to Kraainem: https://www.werkenaandering.be/en/zone-3

E19 Machelen - stackturbine was recently completed. Proposed addition of braiding and C/D lanes on south side of it

A201 Zaventum-Henneaulaan - turbine replaced with SPUI!!! The explanation here suggests a total disconnection with reality:

The redevelopment is based on three key considerations:

1. The layout, size and location of the current turbine node do not meet the requirements for a traffic-safe environment.
2. The distances between the turbine junction and the interchange between the Brussels Ring Road and the E19, as well as the distance between the turbine junction and the Henneaulaan connection complex, are too short. As a result, drivers often have to quickly change lanes at too short a distance.
3. The existing turbine flyover is in poor condition and is in urgent need of replacement. The current condition of the flyover leads to potential safety risks and hinders smooth traffic flow on the Ring around Brussels.
This design and short distances lead to a concentration of traffic accidents and hinder smooth flow on the Ring around Brussels, often resulting in traffic jams. There is an urgent need for restructuring to improve both road safety and traffic flow .

That is why the busy turbine junction is being transformed into a beautiful city boulevard, complete with a green park and an openwork Woluwe.

How beautiful is it really going to be with all the traffic from a major international airport and arterial motorway queuing at traffic lights? The only way this would make any sense is if traffic on the A201 was being drastically reduced, e.g., by relocating the airport access. But the FAQ makes it clear this isn't happening:

Won't the new traffic interchange at the airport (SPI with traffic lights) cause additional traffic jams?
The traffic analyzes show that the SPI traffic lights will not cause structural traffic jams. The current major problem is the limited capacity of the R0. Thanks to the compact design of the junction, we get more space on the R0, which will allow it to function better. This also allows the new connection complex to handle more traffic.
Will the A201 remain the only road to the airport?
Yes, the A201 indeed remains the main access road to Brussels Airport. However, we also take local roads and traffic through the center of Zaventem into account. During the construction phase we discussed measures to discourage cut-through traffic. In addition, the measures taken on the R0 are aimed at smoothing traffic on the R0 and the interchange with the E40. This would reduce the need for alternative routes via the center of Zaventem.

Surely the lack of R0 junction spacing and capacity should be resolved with braiding and C/D lanes as at other junctions.

E40 St-Stevens-Woluwe - turbine replaced with four level stack. Braiding and C/D lanes added to north side.

Numerous minor junctions are also to be reconstructed in Ring North.

There are additionally changes to several junctions in Ring East. The most eye-catching is E411 Leonard, currently a limited access freeflow junction converted from a stackabout. An unusual offside four level stack is proposed, with much of it underground:

Overall I feel their contractors have taken them for a ride, aiming for a full, complex reconstruction of every junction where problems could instead be solved with an extra couple of ramps. Notably only the minor or detrimental changes like the A201 are being fast tracked: https://www.werkenaandering.be/nl/werke ... astructuur I seriously doubt there are the resources to go round ripping up multiple freeflow junctions to replace them with tunnelled stacks. Belgium is not exactly renowned for generous road budgets.

[Bryn666]

You have to consider that airports are under heavy pressure to reduce their carbon footprints - now given aviation itself is doing next to nothing to reduce its impact that leaves airports and local governments little choice but to discourage all but the most essential car trips to their sites. There are plans for additional tram routes into the airport which would need to cross the turbine interchange. Getting rid of the old junction might seem silly but there are logical reasons for it.

Also, Brussels Airport is hardly Heathrow or Atlanta - it won't fall over because a multi-lane SPUI serves it instead of a turbine. I rather imagine most of its traffic is surburban commuters using the R22 connection which will be removed from the ring road.

[Chris5156]

Overall I feel their contractors have taken them for a ride, aiming for a full, complex reconstruction of every junction where problems could instead be solved with an extra couple of ramps.

There's some good stuff in there, but I agree that someone somewhere is having a laugh. What a weird set of plans. What is the rationale for rebuilding a stack-turbine into a stack? It's a freeflowing junction and it works; I can only rationalise it by thinking that the bridges might be life-expired and it's easier to replace them with new ones on a new alignment to keep traffic flowing during the works. But there must be other ways to achieve what they're trying to do.

Still... comforting that we're not the only ones pouring huge resources into road projects that deliver middling benefits

[Bryn666]

Overall I feel their contractors have taken them for a ride, aiming for a full, complex reconstruction of every junction where problems could instead be solved with an extra couple of ramps.

There's some good stuff in there, but I agree that someone somewhere is having a laugh. What a weird set of plans. What is the rationale for rebuilding a stack-turbine into a stack? It's a freeflowing junction and it works; I can only rationalise it by thinking that the bridges might be life-expired and it's easier to replace them with new ones on a new alignment to keep traffic flowing during the works. But there must be other ways to achieve what they're trying to do.

Still... comforting that we're not the only ones pouring huge resources into road projects that deliver middling benefits

Looking at the plans the proposal is to tunnel some of the new slips which is presumably a way to improve the visual amenity and perhaps reduce noise from the interchange permeating into the local area. It does feel rather like a huge expense for little gain but the layout is simpler and neater than the current jumble of slip roads even if they are free-flowing.

Replacing R0/A12 as a stack is a huge improvement though!

[owen b]

I lived in Brussels (Schaerbeek commune) from 1994-1996 and worked just off the R22 Boulevard de la Woluwe south of the E40. I had colleagues who commuted from the Antwerp area and as one of the more junior staff I was sometimes asked to pick people up from the airport. Even 30 years ago, the E40 to E19 of the ring road R0 was very busy, especially at rush hour, and with the closely spaced junctions, many lanes and carriageways and complex layouts the area felt like something out of Los Angeles. Congestion was a frequent explanation for colleagues arriving at work late.

Evidently, and as others have pointed out, the main priorities here seem to be to replace life expired junctions and structures and to maximise throughput on the mainline of the ring road. In general, I'm surprised at the huge scale of the proposed changes.

The A201 from the airport, over the ring road, past NATO to the middle ring R21 is not very high standard, mostly D2 with some parallel C/D carriageways for local access. The roundabout GSJ with the N262 (last junction before the airport) was built during my time in Brussels, prior to that it was a signalised crossroads. The GSJ at the NATO HQ is more recent. In my experience, the A201 would not be used for airport to / from city centre traffic, as the E40 is far superior for that movement (it had six carriageways of two lanes each at the middle ring end during my time in Brussels, although I can see that some of the lanes on the inbound carriageways have been painted over since then), so most of the traffic at that junction I'm sure is turning traffic. All the same, I'm surprised that the junction with the ring road is being replaced with a SPUI. I can kind of see the logic though.

The Ring East (N3 to the E411 and then south towards Waterloo) goes through a forested area which used to remind me of Epping Forest, and I can understand why any changes at the E411 junction would be designed to be compact and well hidden with as little additional above ground land take as possible.

[Peter Freeman]

Overall I feel their contractors have taken them for a ride, aiming for a full, complex reconstruction of every junction where problems could instead be solved with an extra couple of ramps. Notably only the minor or detrimental changes like the A201 are being fast tracked: https://www.werkenaandering.be/nl/werke ... astructuur

Overall, I agree, in that I too would expect significant savings could be made by doing tweaks to certain of the major free-flow interchanges instead of (apparently) complete rebuilds. Perhaps they will do some value-engineering as detailed planning progresses. BTW, I haven't looked at all the plans - there are some really large pdf's in there!

GMaps' typical-traffic shows serious congestion on the NW and NE quadrants of R0 at both peaks and in-between. It's red-stained to the same unfortunate degree as north & west M60 in Manchester, and the more embarrassing parts of Melbourne and Sydney. It seems though that even the fast-tracked components will take a few years, so full completion is presumably at least a decade away, and a lot can change in a decade: economic situation, flashes of realism, etc.

Surely the lack of R0 junction spacing and capacity [at R201] should be resolved with braiding and C/D lanes as at other junctions.

You'd think so, but maybe not. There's already braiding and C/Ds. There is congestion there, but it's more on R0's mainline, not the interchange or C/D. Hence they want to widen R0 by gobbling up the current C/Ds at that point.

R201 traffic probably turns rather than flows through (as 201 eventually degrades, and Owen b opined that E40 is better into the city), and one medium airport can only generate so much traffic (201 outbound goes nowhere else). Therefore, proposing what would normally be a service-interchange type is not so crazy.

From the linked video, you can see that the proposed SPUI is quite large-scale and smoothly-shaped and therefore fast-flowing, unlike most urban ones (the blurb uses 'SPI', not 'SPUI'). The south-facing SPI ramps will still feed into C/Ds. On top of all that, the projected nearby eco-benefits are obviously highly valued.

This is reminiscent of my suggestion for a SPUI at Denton Island, rather than completing that location with the intended flyover. Why am I so prepared to sacrifice freeflow? A: Because we on Sabre, and perhaps NH, over-rate it. Freeflow is nice - who likes to stop, wait and start again during a journey, even if it is only for a minute or two? But what actually matters is journey-time and investment value-for-money. Our focus should be on outcomes, not the means.

I've only been to Brussels once, just after the Chunnel opened nearly 30 years ago. I was on a UK visit, so I undertook a day-jaunt on Le Shuttle to see the 'Atomium' (really, for the journey and the drive). It was my first drive in Europe. I hardly knew where I was going, and I was unexpectedly delighted to find myself driving through an impressive road tunnel. I think it was somewhere on a ring road, but now I'm unsure exactly where.

(edit: paragraphing)

[owen b]

I've only been to Brussels once, just after the Chunnel opened nearly 30 years ago. I was on a UK visit, so I undertook a day-jaunt on Le Shuttle to see the 'Atomium' (really, for the journey and the drive). It was my first drive in Europe. I hardly knew where I was going, and I was unexpectedly delighted to find myself driving through an impressive road tunnel. I think it was somewhere on a ring road, but now I'm unsure exactly where.

Brussels has several impressive urban road tunnels. If you head straight from the E40 from Ostend direction over the R0 towards the centre of Brussels it's not long before you end up in a tunnel which ends up on the north side of the inner ring. The inner ring is an imperfect pentagon, and the north, east and south east sides have impressive urban GSJs and underpasses / tunnels. The E40 from the east ends at an impressive complex many stranded GSJ on the middle (incomplete) ring, from where free flow road tunnels head towards the city centre.

There are various obvious questions about the Brussels road network, and I've never got round to even a cursory look for answers, but the most obvious questions to me are :
i) what happened to any plans to complete the R0 as a true ring road, rather than with the obvious bodge on the southern side all the way south beyond Waterloo?
ii) what plans were there for an urban extension to the E19 on the north side? (The current GSJ looks like fairly obvious unfinished business on the city side).
iii) what plans were there to upgrade the south west and north west sides of the inner ring up to a similar level as the rest of it?

[Bryn666]

I've only been to Brussels once, just after the Chunnel opened nearly 30 years ago. I was on a UK visit, so I undertook a day-jaunt on Le Shuttle to see the 'Atomium' (really, for the journey and the drive). It was my first drive in Europe. I hardly knew where I was going, and I was unexpectedly delighted to find myself driving through an impressive road tunnel. I think it was somewhere on a ring road, but now I'm unsure exactly where.

Brussels has several impressive urban road tunnels. If you head straight from the E40 from Ostend direction over the R0 towards the centre of Brussels it's not long before you end up in a tunnel which ends up on the north side of the inner ring. The inner ring is an imperfect pentagon, and the north, east and south east sides have impressive urban GSJs and underpasses / tunnels. The E40 from the east ends at an impressive complex many stranded GSJ on the middle (incomplete) ring, from where free flow road tunnels head towards the city centre.

There are various obvious questions about the Brussels road network, and I've never got round to even a cursory look for answers, but the most obvious questions to me are :
i) what happened to any plans to complete the R0 as a true ring road, rather than with the obvious bodge on the southern side all the way south beyond Waterloo?
ii) what plans were there for an urban extension to the E19 on the north side? (The current GSJ looks like fairly obvious unfinished business on the city side).
iii) what plans were there to upgrade the south west and north west sides of the inner ring up to a similar level as the rest of it?

There's a bridge to nowhere on the west side of R0 which is currently a car park. This was was the intended branch of the ring to cross the south side of Brussels. The run through the forest and massive loop to the south is a bodge job of M25 proportions.

The E19/A1 was intended to be a four carriageway superhighway up to Mechelen, you can see lots of evidence of this even where the new high speed railway has been threaded across it. I don't have any plans but my understanding is the city extension was intended to reach the central ring road, probably following the N1 corridor.

I'm not sure there were any plans for the west side of the central ring - the tunnels have been taking the bulk of traffic since they opened.

[Peter Freeman]

I've only been to Brussels once ... and I was unexpectedly delighted to find myself driving through an impressive road tunnel. I think it was somewhere on a ring road, but now I'm unsure exactly where.

Brussels has several impressive urban road tunnels. If you head straight from the E40 from Ostend direction over the R0 towards the centre of Brussels it's not long before you end up in a tunnel which ends up on the north side of the inner ring.

Yep, that would be the one.

[jackal]

Surely the lack of R0 junction spacing and capacity [at R201] should be resolved with braiding and C/D lanes as at other junctions.

You'd think so, but maybe not. There's already braiding and C/Ds. There is congestion there, but it's more on R0's mainline, not the interchange or C/D. Hence they want to widen R0 by gobbling up the current C/Ds at that point.

There are no C/D lanes to the north and no braiding except for the R22 junction, which is being removed, and its braiding with it - I assume because the recently completed E19 stackturbine provides some of that connectivity.

The big issue they foreground is the weaving up to the E19 stackturbine, and there is zero braiding or C/D lanes for that. It's blindingly obvious that that is the solution, not least because that's what they have on adjoining sections of R0. The to-be-removed R22 braiding on the west side could also be quite simply utilised for R0/A201 braiding. I just think the consultants aren't up to anything more complex or site specific than plonking down a cookie cutter stack or service interchange, and a stack didn't fit here.

R201 traffic probably turns rather than flows through (as 201 eventually degrades, and Owen b opined that E40 is better into the city), and one medium airport can only generate so much traffic (201 outbound goes nowhere else). Therefore, proposing what would normally be a service-interchange type is not so crazy.

There will be loads of straight-over traffic - people tend to underestimate this, I find (e.g., Simister Island or Brenley Corner). But even setting that aside, an SPUI is vastly worse for turning traffic than a turbine. You are losing four free flow long turns (left in Belgium) as well as the two straightovers. It's a really dramatic reduction in service provision.

Brussels Airport is in the same ballpark as Manchester. Suppose they'd completed M56 J5 with a motorway coming out to the NW as was planned. Nothing massively strategically important, you'd still take the M56 to get to most of the city, but it would link into various suburbs and be pretty busy. What would we then think of the proposal to replace the freeflow junction with an SPUI? We would think it was total insanity, and rightly so. Indeed, even without the extra motorway it would be stupid to foul up the airport access, and we've complained many times about precisely that a little further along the spur.

This is reminiscent of my suggestion for a SPUI at Denton Island, rather than completing that location with the intended flyover. Why am I so prepared to sacrifice freeflow? A: Because we on Sabre, and perhaps NH, over-rate it. Freeflow is nice - who likes to stop, wait and start again during a journey, even if it is only for a minute or two? But what actually matters is journey-time and investment value-for-money. Our focus should be on outcomes, not the means.

I think that's okay as a proposal at Denton because an SPUI is an upgrade on a 2BR. But it's a big downgrade on a turbine with vastly longer journey times. Do I really need to say this?

If NH came up with a proposal like this, based on medieval torture of traffic models, you'd all be livid. "Only on Britain would we replace a freeflow junction between two motorways with traffic lights". It gets a pass because it's in Belgium.

[Bryn666]

Surely the lack of R0 junction spacing and capacity [at R201] should be resolved with braiding and C/D lanes as at other junctions.

You'd think so, but maybe not. There's already braiding and C/Ds. There is congestion there, but it's more on R0's mainline, not the interchange or C/D. Hence they want to widen R0 by gobbling up the current C/Ds at that point.

There are no C/D lanes to the north and no braiding except for the R22 junction, which is being removed, and its braiding with it - I assume because the recently completed E19 stackturbine provides some of that connectivity.

The big issue they foreground is the weaving up to the E19 stackturbine, and there is zero braiding or C/D lanes for that. It's blindingly obvious that that is the solution, not least because that's what they have on adjoining sections of R0. The to-be-removed R22 braiding on the west side could also be quite simply utilised for R0/A201 braiding. I just think the consultants aren't up to anything more complex or site specific than plonking down a cookie cutter stack or service interchange, and a stack didn't fit here.

R201 traffic probably turns rather than flows through (as 201 eventually degrades, and Owen b opined that E40 is better into the city), and one medium airport can only generate so much traffic (201 outbound goes nowhere else). Therefore, proposing what would normally be a service-interchange type is not so crazy.

There will be loads of straight-over traffic - people tend to underestimate this, I find (e.g., Simister Island or Brenley Corner). But even setting that aside, an SPUI is vastly worse for turning traffic than a turbine. You are losing four free flow long turns (left in Belgium) as well as the two straightovers. It's a really dramatic reduction in service provision.

Brussels Airport is in the same ballpark as Manchester. Suppose they'd completed M56 J5 with a motorway coming out to the NW as was planned. Nothing massively strategically important, you'd still take the M56 to get to most of the city, but it would link into various suburbs and be pretty busy. What would we then think of the proposal to replace the freeflow junction with an SPUI? We would think it was total insanity, and rightly so. Indeed, even without the extra motorway it would be stupid to foul up the airport access, and we've complained many times about precisely that a little further along the spur.

This is reminiscent of my suggestion for a SPUI at Denton Island, rather than completing that location with the intended flyover. Why am I so prepared to sacrifice freeflow? A: Because we on Sabre, and perhaps NH, over-rate it. Freeflow is nice - who likes to stop, wait and start again during a journey, even if it is only for a minute or two? But what actually matters is journey-time and investment value-for-money. Our focus should be on outcomes, not the means.

I think that's okay as a proposal at Denton because an SPUI is an upgrade on a 2BR. But it's a big downgrade on a turbine with vastly longer journey times. Do I really need to say this?

If NH came up with a proposal like this, based on medieval torture of traffic models, you'd all be livid. "Only on Britain would we replace a freeflow junction between two motorways with traffic lights". It gets a pass because it's in Belgium.

It's nothing about getting a pass because it's in Belgium - re-read what was posted upthread about airports and vehicle access. This is the same reason Heathrow T6 was going to have bad road access - airports cannot meet their carbon targets unless they stop people arriving by car because aviation companies won't do their part to reduce emissions. I seem to recall Heathrow was even considering a congestion charge of something bonkers like £20-30 per vehicle at one point, they're also restricted on the number of airport related parking spaces (they can't exceed the current 51,000 or whatever number it is).

Land is needed for rail and tram improvements, and the A201 is all of 5km long and a dead end with traffic lights at the western end anyway.

I really don't see the problem with this particular change, it's a waste of land at the moment and could be better used by more efficient means to connecting central Brussels to the airport. The rest of the project demonstrates they're not trying to screw over traffic on the ring road elsewhere, they're just doing what most European airports are mandated to do - cut emissions.

As for M56 J5, if it had been completed as you say there'd have been no access to the west of the M56 anyway, so it's a false comparison - what is there now is as intended barring the Western Parkway continuing across. Making it a SPUI would've improved connectivity in that situation.

[owen b]

Brussels Airport is in the same ballpark as Manchester. Suppose they'd completed M56 J5 with a motorway coming out to the NW as was planned. Nothing massively strategically important, you'd still take the M56 to get to most of the city, but it would link into various suburbs and be pretty busy. What would we then think of the proposal to replace the freeflow junction with an SPUI? We would think it was total insanity, and rightly so. Indeed, even without the extra motorway it would be stupid to foul up the airport access, and we've complained many times about precisely that a little further along the spur.

I find the decision to replace the junction with a SPUI surprising, and I'm not knowledgeable enough about the traffic flows and various other considerations to take a clear view one way or the other. However, I note that Brussels airport is somewhere between Luton and Manchester airports for passenger traffic, so yes, I accept that Manchester is a fair comparator, but so is Luton. To get from M1 northbound to Luton airport you have to go through a signalised roundabout GSJ (M1 J10), a flat signalised junction (B653 link), and a flat roundabout (airport end of the A1081). The lights at the B653 turn replaced a roundabout.

It would be interesting to see the stats for the various flows at the R0 / A201 GSJ. While I am sure there must be a significant amount of straight ahead A201 traffic I'd be surprised if it wasn't greatly outnumbered by turning traffic. On the city side of the R0 my experience was that the A201 was basically a local distributor for Evere, the NATO area and parts of Schaerbeek. It really wasn't much use for anything else.

[jackal]

You'd think so, but maybe not. There's already braiding and C/Ds. There is congestion there, but it's more on R0's mainline, not the interchange or C/D. Hence they want to widen R0 by gobbling up the current C/Ds at that point.

There are no C/D lanes to the north and no braiding except for the R22 junction, which is being removed, and its braiding with it - I assume because the recently completed E19 stackturbine provides some of that connectivity.

The big issue they foreground is the weaving up to the E19 stackturbine, and there is zero braiding or C/D lanes for that. It's blindingly obvious that that is the solution, not least because that's what they have on adjoining sections of R0. The to-be-removed R22 braiding on the west side could also be quite simply utilised for R0/A201 braiding. I just think the consultants aren't up to anything more complex or site specific than plonking down a cookie cutter stack or service interchange, and a stack didn't fit here.

R201 traffic probably turns rather than flows through (as 201 eventually degrades, and Owen b opined that E40 is better into the city), and one medium airport can only generate so much traffic (201 outbound goes nowhere else). Therefore, proposing what would normally be a service-interchange type is not so crazy.

There will be loads of straight-over traffic - people tend to underestimate this, I find (e.g., Simister Island or Brenley Corner). But even setting that aside, an SPUI is vastly worse for turning traffic than a turbine. You are losing four free flow long turns (left in Belgium) as well as the two straightovers. It's a really dramatic reduction in service provision.

Brussels Airport is in the same ballpark as Manchester. Suppose they'd completed M56 J5 with a motorway coming out to the NW as was planned. Nothing massively strategically important, you'd still take the M56 to get to most of the city, but it would link into various suburbs and be pretty busy. What would we then think of the proposal to replace the freeflow junction with an SPUI? We would think it was total insanity, and rightly so. Indeed, even without the extra motorway it would be stupid to foul up the airport access, and we've complained many times about precisely that a little further along the spur.

This is reminiscent of my suggestion for a SPUI at Denton Island, rather than completing that location with the intended flyover. Why am I so prepared to sacrifice freeflow? A: Because we on Sabre, and perhaps NH, over-rate it. Freeflow is nice - who likes to stop, wait and start again during a journey, even if it is only for a minute or two? But what actually matters is journey-time and investment value-for-money. Our focus should be on outcomes, not the means.

I think that's okay as a proposal at Denton because an SPUI is an upgrade on a 2BR. But it's a big downgrade on a turbine with vastly longer journey times. Do I really need to say this?

If NH came up with a proposal like this, based on medieval torture of traffic models, you'd all be livid. "Only on Britain would we replace a freeflow junction between two motorways with traffic lights". It gets a pass because it's in Belgium.

It's nothing about getting a pass because it's in Belgium - re-read what was posted upthread about airports and vehicle access. This is the same reason Heathrow T6 was going to have bad road access - airports cannot meet their carbon targets unless they stop people arriving by car because aviation companies won't do their part to reduce emissions. I seem to recall Heathrow was even considering a congestion charge of something bonkers like £20-30 per vehicle at one point, they're also restricted on the number of airport related parking spaces (they can't exceed the current 51,000 or whatever number it is).

Land is needed for rail and tram improvements, and the A201 is all of 5km long and a dead end with traffic lights at the western end anyway.

I really don't see the problem with this particular change, it's a waste of land at the moment and could be better used by more efficient means to connecting central Brussels to the airport. The rest of the project demonstrates they're not trying to screw over traffic on the ring road elsewhere, they're just doing what most European airports are mandated to do - cut emissions.

This is a road improvement by a road authority, which is supposed to improve conditions for road users. See quotes and links in OP.

Your response seems ambiguous between

1. Agreeing with the road authority (and perhaps Peter) that this is an efficient improvement in terms of highways access. Your last para above suggests this interpretation.

2. Agreeing with me that this is an inefficient improvement in terms of highways access. Note that one reason why an improvement might be inefficient in terms of highway access is as a deterrent to promote other transport modes (though to repeat, this is not a reason actually given for this improvement). Your first two paras suggest this interpretation.

Care to clarify?

Or to put it another way, you can't have your cake (deterring vehicular airport access) and eat it (efficient vehicular airport access).

[Bryn666]

There are no C/D lanes to the north and no braiding except for the R22 junction, which is being removed, and its braiding with it - I assume because the recently completed E19 stackturbine provides some of that connectivity.

The big issue they foreground is the weaving up to the E19 stackturbine, and there is zero braiding or C/D lanes for that. It's blindingly obvious that that is the solution, not least because that's what they have on adjoining sections of R0. The to-be-removed R22 braiding on the west side could also be quite simply utilised for R0/A201 braiding. I just think the consultants aren't up to anything more complex or site specific than plonking down a cookie cutter stack or service interchange, and a stack didn't fit here.

There will be loads of straight-over traffic - people tend to underestimate this, I find (e.g., Simister Island or Brenley Corner). But even setting that aside, an SPUI is vastly worse for turning traffic than a turbine. You are losing four free flow long turns (left in Belgium) as well as the two straightovers. It's a really dramatic reduction in service provision.

Brussels Airport is in the same ballpark as Manchester. Suppose they'd completed M56 J5 with a motorway coming out to the NW as was planned. Nothing massively strategically important, you'd still take the M56 to get to most of the city, but it would link into various suburbs and be pretty busy. What would we then think of the proposal to replace the freeflow junction with an SPUI? We would think it was total insanity, and rightly so. Indeed, even without the extra motorway it would be stupid to foul up the airport access, and we've complained many times about precisely that a little further along the spur.

I think that's okay as a proposal at Denton because an SPUI is an upgrade on a 2BR. But it's a big downgrade on a turbine with vastly longer journey times. Do I really need to say this?

If NH came up with a proposal like this, based on medieval torture of traffic models, you'd all be livid. "Only on Britain would we replace a freeflow junction between two motorways with traffic lights". It gets a pass because it's in Belgium.

It's nothing about getting a pass because it's in Belgium - re-read what was posted upthread about airports and vehicle access. This is the same reason Heathrow T6 was going to have bad road access - airports cannot meet their carbon targets unless they stop people arriving by car because aviation companies won't do their part to reduce emissions. I seem to recall Heathrow was even considering a congestion charge of something bonkers like £20-30 per vehicle at one point, they're also restricted on the number of airport related parking spaces (they can't exceed the current 51,000 or whatever number it is).

Land is needed for rail and tram improvements, and the A201 is all of 5km long and a dead end with traffic lights at the western end anyway.

I really don't see the problem with this particular change, it's a waste of land at the moment and could be better used by more efficient means to connecting central Brussels to the airport. The rest of the project demonstrates they're not trying to screw over traffic on the ring road elsewhere, they're just doing what most European airports are mandated to do - cut emissions.

This is a road improvement by a road authority, which is supposed to improve conditions for road users. See quotes and links in OP.

Your response seems ambiguous between

1. Agreeing with the road authority (and perhaps Peter) that this is an efficient improvement in terms of highways access. Your last para above suggests this interpretation.

2. Agreeing with me that this is an inefficient improvement in terms of highways access. Note that one reason why an improvement might be inefficient in terms of highway access is as a deterrent to promote other transport modes (though to repeat, this is not a reason actually given for this improvement). Your first two paras suggest this interpretation.

Care to clarify?

Or to put it another way, you can't have your cake (deterring vehicular airport access) and eat it (efficient vehicular airport access).

You are applying the narrowest possible metric that only fully free-flowing interchanges improve conditions for road users, which is a falsehood in itself as you have to apply something called "context". In this case that being airport access by other modes is becoming the general European priority hence why they are freeing up space for the tram and rail improvements (these are the more efficient modes of access to the airport which any sane transport planner will tell you is not private cars). The giant turbine interchange is in the way of a direct tram connection as planned, the SPUI frees up space for that and takes the R22 movement out of the equation entirely (R22 is having separate improvement schemes including a lengthy new tunnel opened at the A1 interchange).

The airport itself advises all the options to get there: https://www.brusselsairport.be/en/passe ... ss-parking - given they only have 10,000 spaces compared to Manchester's 22,000, it's fairly obvious that car travel isn't their preferred method anyway.

Luton, for comparison, appears to have a similar number of spaces to Brussels.

As Owen states, the A201 is simply not a strategic road, it's AADT is 36,000 at Zaventem, it will not be made unbearable by removing lengths of elevated slip roads built in the 60s that are a vast drain on finances to maintain for little benefit to the wider city region.

US highway guidance says a SPUI can handle traffic in the 25,000-35,000 AADT range quite comfortably. If the free-flow loving Americans think that, then I am sure a SPUI here in a European context of traffic reduction and modal shift will be fine.

[jackal]

Well 36k>25k-35k. Then add on some growth. Not to mention the other side of the A201 may be more than 36k. As Owen mentions, it would be good to see all the counts.

Also, even if the SPUI is in capacity (in the sense that there's enough stacking space that things don't break down completely), journey times are still much longer where, on average, <1/3 of the time is green rather than all of the time at a turbine. And airport access has a disproportionate economic effect. There's a reason why even quite modest AADT airport accesses are freeflow in almost all developed countries.

Carbon emissions are very relevant of course, though it mostly seems to be a UK thing (derived from the Heathrow expansion psychodrama) to focus on the miniscule emissions from vehicular airport access while ignoring the vastly larger emissions from flights, not to mention the rest of the road network. If we're saying there is low airport AADT, we're also saying there's low emissions - which still should be considered in the overall planning equation, but only at their actual level of importance.

As for public transport, I've used the train from Brussels airport into the city centre several times, and it also has direct access to Antwerp, Ghent, and Leuven among others. It's already great access compared to UK airports and a tram will be slower and not really a game changer, though to be sure it will be useful for the suburbs it serves - a bit like the Manchester airport tram I suppose. (As an aside, trains in Brussels are not the pleasant experience they are in most European cities, which might be a better area of investment than digging up turbines and stackturbines.)

[Peter Freeman]

OK, I'll eat humble pie and retract on this one. My reading of the R201 issue wasn't in sufficient depth. There's a lot to take in all at once in that documentation!

You're right that I didn't look carefully enough at the outer carriageways under the R201 interchange. Indeed they are not C/Ds, but rather an extended run of R22 parallel to R0 for quite some way, before it eventually leaves that line by swinging SW. Those carriageways will be removed and R0 widened.

Whether R201 interchange is kept as-is, or replaced by a SPUI, there will still be a weaving issue between it and E19 interchange, and, as you say, it requires simply a braid to solve it. Similarly for the inadequate weaving length between R201 and Hector Henneaulaan, and similarly for the weave between there and E40. And then, given those additions, and the fact that the central bridge needs to be replaced for age anyway and could be longer, R22 could actually stay roughly where it is (and be partially borrowed for the braid, as you suggest).

There is no lack of space at any of the locations under discussion. At R201 they seem determined to make extra accessible greenery around a rather small waterway, but even that doesn't require abandonment of the current turbine.

So I'll withdraw my concession to their plan, and agree with you Jackal - as I already did for some of their other over-the-top plans. Kom - ons moet aan de ring werk!

Regarding Bryn's alternative mode access to the airport, I fully support non-car options, but I think we can, and should, retain all modes. I've never seen road provision as being in competition with public transport - or bikes, Bryn.

I will maintain my general, and firmly held, view that we should not overlook non-freeflow and even non-GSJ solutions where they are adequate. Australia, and the UK, actually do subscribe to this - the problem in the UK is that the occurrences all-too-often are rotary. AU's menu adds diamond, DDI and SPUI.

If there was not already a full-freeflow interchange between R0 and R201, what would we think appropriate to build from scratch? This, bearing in mind R201's degradation to non-GSJ only 4km to the SW, and the fact that it serves only the airport 2km to the NE. I do think a DDI or SPUI would suffice.

[Peter Freeman]

Also, even if the SPUI is in capacity (in the sense that there's enough stacking space that things don't break down completely), journey times are still much longer where, on average, <1/3 of the time is green rather than all of the time at a turbine.

An unbalanced SPUI with smart signals can provide much better than 1/3 duty cycle to the heaviest flow. Discussion for another place.

[jackal]

^ Which is why I said average. It's also speculative that flows are particularly imbalanced here.

Anyway, thanks for your thoughts, Peter. I still think it would be nuts to build an SPUI here from scratch - it's a UK speciality to have grade-separated roads connected with traffic lights and far from international norms. And 36k is plenty for a grade-separated road in developed countries other than the UK (and even here pretty often).

[Bryn666]

^ Which is why I said average. It's also speculative that flows are particularly imbalanced here.

Anyway, thanks for your thoughts, Peter. I still think it would be nuts to build an SPUI here from scratch - it's a UK speciality to have grade-separated roads connected with traffic lights and far from international norms. And 36k is plenty for a grade-separated road in developed countries other than the UK (and even here pretty often).

But this is the point, the A201 is not a lengthy grade separated road - you have a turbine serving a road that turns into a city street less than 2 miles to the west, so it gains very little for the network other than a huge maintenance cost. It's some of the oldest motorway infrastructure in Belgium, built at a time when cars were king and nothing else mattered - the world has moved on, whether people on SABRE like it or not. Even the USA is rethinking giant free-flow interchanges where they are expensive to maintain and not helpful to traffic - a current example being this:

https://www.memphisflyer.com/whatever-h ... nterchange

You could argue they should've replaced the cloverleaf with a turbine or a stack but they've gone with the critical movements only - I-55. Much like how the SPUI is going with the critical movements - the R0; which loses a lot of diverge/merge problems and has a clearer run through meaning capacity and safety improves whilst not inducing loads of extra car traffic to an airport Jackal has already conceded has excellent non-car provision to.

[jackal]

^ Which is why I said average. It's also speculative that flows are particularly imbalanced here.

Anyway, thanks for your thoughts, Peter. I still think it would be nuts to build an SPUI here from scratch - it's a UK speciality to have grade-separated roads connected with traffic lights and far from international norms. And 36k is plenty for a grade-separated road in developed countries other than the UK (and even here pretty often).

But this is the point, the A201 is not a lengthy grade separated road - you have a turbine serving a road that turns into a city street less than 2 miles to the west, so it gains very little for the network other than a huge maintenance cost. It's some of the oldest motorway infrastructure in Belgium, built at a time when cars were king and nothing else mattered - the world has moved on, whether people on SABRE like it or not. Even the USA is rethinking giant free-flow interchanges where they are expensive to maintain and not helpful to traffic - a current example being this:

https://www.memphisflyer.com/whatever-h ... nterchange

You could argue they should've replaced the cloverleaf with a turbine or a stack but they've gone with the critical movements only - I-55. Much like how the SPUI is going with the critical movements - the R0; which loses a lot of diverge/merge problems and has a clearer run through meaning capacity and safety improves whilst not inducing loads of extra car traffic to an airport Jackal has already conceded has excellent non-car provision to.

In the Memphis case the only GSJed road is the I-55, ergo they are reconstructing to prioritise the I-55. This is a perfectly normal road upgrade and does not in any way support putting an SPUI where two GSJed roads meet.

And the A201 is definitely GSJed - two GSJs in either direction, and five consecutive GSJs including the turbine. It's quite normal for an airport access to be short but grade separated, likewise for access to other traffic generators like Nato and the various corporate HQs on the city side A201.

I'm stepping out at this point because this discussion isn't going anywhere productive.