M11/N11 - M50 (J4) to Coyne's Cross (J14) [options published]

schmittel wrote: »

Certainly new to me. Is that purple corridor the tunnel?

it's not specified but I assume so as you couldn't build an overground road along that alignment. Probably some sort of scheme update imminent, the map was posted by one of the local reps on FB.

Steve012

loyatemu wrote: »

is this new? interactive map of the current options:
https://atlas-ie.arup.com/portal/apps/webappviewer/index.html?id=a47cd00abeee44a49cfdfed7a8993da8&fbclid=IwAR1hSmO8aFdqtt63AiuJVTy-FFTHjNOYGAuQk1Y67NF9a3HLVs73SPQvn7Q

Looks new it says in the bottom right about the study they are doing now, so prob new

loyatemu wrote: »

is this new? interactive map of the current options:
https://atlas-ie.arup.com/portal/apps/webappviewer/index.html?id=a47cd00abeee44a49cfdfed7a8993da8&fbclid=IwAR1hSmO8aFdqtt63AiuJVTy-FFTHjNOYGAuQk1Y67NF9a3HLVs73SPQvn7Q

First time seeing that purple route. The level of detail on the red route would lead me to think thats the one they're going for, although maybe reading too much into it. Must ask the parents if they've received anything official from arup recently.

Few interesting additions including jn7 link roads. Interesting alignment at jn9 too, possibly for future northern access route to Greystones. Also a link road at jn11 linking Kilquade road to Farrenkelly rd.

prunudo wrote: »

First time seeing that purple route. The level of detail on the red route would lead me to think thats the one they're going for, although maybe reading too much into it. Must ask the parents if they've received anything official from arup recently.

Few interesting additions including jn7 link roads. Interesting alignment at jn9 too, possibly for future northern access route to Greystones. Also a link road at jn11 linking Kilquade road to Farrenkelly rd.

I raised the is red the preferred route because of level of info/detail question in previous discussions with ARUP, and they said that because there is already a road on the ground they are inevitably significantly more informed about what is likely and what is not if they chose that route. They said not to read too much into the level of detail they have with red. Kind of makes sense when you think about it.

I'm currently thinking they are leaning towards cyan route because of the sudden introduction of the tunnel option. This clearly seems like a red herring, it wont be the preferred route, and has been introduced at a late stage in order to justify the preferred route.

If preferred route was red yes they'd have to show that they have considered all possible alternative options in order to justify going through the Glen SAC. But surely if the tunnel is there to tick the all other boxes for the Habitats Directive, they'd have done more public consultations on it and at least appeared to be more thorough etc? If they go red it is inevitable it will end up in court challenged because it is in contravention of European law, so they would need to have crossed every T and dotted every I to defend that challenge.

Which leads me to think it is there to justify the cyan route. If they go for that, there will be a huge uproar about cost, "awful waste of money, when you could have just widened the existing road, we don't need a new motorway", they can say look widening the N11 through the Glen is not an option, and the only other feasible option is a tunnel, and that is three times the cost or whatever.

Possibly overthinking this I admit, but have had plenty of time on my hands!

Many here don't want to hear this but they could go with red but not widen the N11 through the Glen.

schmittel wrote: »

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Personally think, for longevity and future proofing, the cyan route or similar is a better route than what the red route has become.
But, that ship has sailed, its 40 years too late, I think the current cyan route will meet a lot of local opposition, but then the red route will meet outside opposition and more likely to end up in the courts. Its going to be a conundrum for the designers, thats for sure.

Pete_Cavan wrote: »

Many here don't want to hear this but they could go with red but not widen the N11 through the Glen.

Interestingly, that thought crossed my mind recently too, widening as far as jn10, new northern link road to Greystones and let the future politicians worry about jn10-14 in 2040.

prunudo wrote: »

Personally think, for longevity and future proofing, the cyan route or similar is a better route than what the red route has become.
But, that ship has sailed, its 40 years too late, I think the current cyan route will meet a lot of local opposition, but then the red route will meet outside opposition and more likely to end up in the courts. Its going to be a conundrum for the designers, thats for sure.

Agree on the cyan route, it's a far better long term solution.

They'll meet opposition whichever way they go.

Cyan opposition will be largely disgruntled locals bearing the brunt of the CPOs. Their case will be principally property rights etc.

Red opposition will have a stronger case, be better funded, better organised with a larger reach.

I think they'll have a far harder job overcoming the opposition to the red route.

Pete_Cavan wrote: »

Many here don't want to hear this but they could go with red but not widen the N11 through the Glen.

I really hope they're not that stupid. But looking at their interactive map, their corridor certainly narrows through the Glen to very little more than is there already!

Chris_5339762

I think it'll be the red route purely for sanity reasons. The N11 through the Glen is just too new to replace with an offline route.

That said.. widening it... maybe by a token amount? Fit in three narrow M50 width lanes into a very slightly widened corridor?

L1011

Chris_5339762 wrote: »

I think it'll be the red route purely for sanity reasons. The N11 through the Glen is just too new to replace with an offline route.

That said.. widening it... maybe by a token amount? Fit in three narrow M50 width lanes into a very slightly widened corridor?

All of the uproar for little of the benefit.

Also doesn't deal with the entrance from the S/B side which would be ever more dangerous on a three lane road; the onslips on the N/B side would be very dangerous on a narrow three laner too.

L1011 wrote: »

All of the uproar for little of the benefit.

Also doesn't deal with the entrance from the S/B side which would be ever more dangerous on a three lane road; the onslips on the N/B side would be very dangerous on a narrow three laner too.

they can move the forest car park. the only on-ramp right at the Glen is J10 and I assume they'll be closing the Old Downs Rd turn adjacent to it which will make more space.

(J10 is a mess of old roads really, it might be better if they closed it and built a link road from there to J11 for access to Delgany. The roundabout at J11 already has unused arms for that and a link to Kilquade).

Like this:

loyatemu wrote: »

they can move the forest car park. the only on-ramp right at the Glen is J10 and I assume they'll be closing the Old Downs Rd turn adjacent to it which will make more space.

(J10 is a mess of old roads really, it might be better if they closed it and built a link road from there to J11 for access to Delgany. The roundabout at J11 already has unused arms for that and a link to Kilquade).

Like this:

Not sure why a parallel link road isn't or hasn't been looked at in the past.
I believe a flyover at the old Drummin junction is planned to connect Willow and Delgany. That would allow Barry's bridge to become one way and return to being used as an on ramp. ( is my mind getting fuzzy or was it origanlly one way, can't remember).

Also agree on moving the forest car park. Makes far more sense to move it to the rear of the woods with direct access from jn9, safer both for traffic movements and security but also allows for more space and even future opportunities for venders/other service's.

prunudo wrote: »

Not sure why a parallel link road isn't or hasn't been looked at in the past.
I believe a flyover at the old Drummin junction is planned to connect Willow and Delgany. That would allow Barry's bridge to become one way and return to being used as an on ramp. ( is my mind getting fuzzy or was it origanlly one way, can't remember).

Loyatemu's suggestion looks like a neater job than a flyover to achieve the same thing.

schmittel wrote: »

Loyatemu's suggestion looks like a neater job than a flyover to achieve the same thing.

I agree, just not sure why they've really explored this option.
Parallel link roads would solve a lot of the congestion issues at peak times. There are far too many local traffic movements interacting with mainline traffic which in turns contributes to the stop start nature of traffic flow.
Netwown/Kilpedder/Willow grove residents going to Greystones/Delgany (Jn12-jn10). Roundwood/Kilmacanogue residents going to Bray (jn8 -jn 7) and Enniskerry residents goings Bray also (20 bends to jn6).
Also people turning off to Enniskerry, going from mainline or from jn7 are at odds with movements of traffic joining mainline from jn7.
When you actually sit down and think about it the whole section of road is a shambles. Doesnt know whether its a main interurban or a local road.

prunudo wrote: »

I agree, just not sure why they've really explored this option.
Parallel link roads would solve a lot of the congestion issues at peak times. There are far too many local traffic movements interacting with mainline traffic which in turns contributes to the stop start nature of traffic flow.
Netwown/Kilpedder/Willow grove residents going to Greystones/Delgany (Jn12-jn10). Roundwood/Kilmacanogue residents going to Bray (jn8 -jn 7) and Enniskerry residents goings Bray also (20 bends to jn6).
Also people turning off to Enniskerry, going from mainline or from jn7 are at odds with movements of traffic joining mainline from jn7.
When you actually sit down and think about it the whole section of road is a shambles. Doesnt know whether its a main interurban or a local road.

Yep totally agree with all of the above which is why I think the best solution is focus turning that stretch of N11 into a road that serves the local traffic and go with the cyan for interurban traffic.

It just seems so obvious. I'm not sure the cost would be much higher either by the time you mess about with flyovers and parallel link roads to try and solve both problems.

prunudo wrote: »

That would allow Barry's bridge to become one way and return to being used as an on ramp. ( is my mind getting fuzzy or was it origanlly one way, can't remember).

Barry's Bridge was built in the 70s and you're right it was one-way until about 10 years ago when they built an exit lane there to (belatedly) replace the closed median crossing at Willow Grove. The local bus service (184) still doesn't use the new slip road though, it goes up to the Glenview, does a u-turn and exits on the southbound side.

They left several minor accesses along that stretch that should have been closed when J11 opened, at Kilpedder, Willow Grove and Old-Downs road.

You can't walk or cycle from Newtown to Kilpedder without using the N11, which is ridiculous, a short link road from J12 is needed. And whilst you can walk from Willow Grove to Delgany via Barry's Bridge, you can't cycle that way so have to take a massive detour via the R774 or cycle along the N11.

I've no problem with them fixing these local access issues, which will in turn improve traffic flow on the N11, but I'm still not in favour of a massive expensive upgrade of the dualler itself (particularly not the cyan route which would involve blowing huge holes in Downs Hill).

Like I've said before on here, I think the cyan route is the better route, but its too late for that. If they are going to cpo huge chucks of countryside it should be for a new trainline (I know that will be multi billion price tag).
Link roads, closing unnecessary junctions and entrances plus making best use of the existing corridor is the way to see this through. And I say that as someone who's family home will be effected by the red route.

Times report on the tunnel option:
https://www.irishtimes.com/news/ireland/irish-news/details-of-new-road-tunnel-at-glen-of-the-downs-released-1.4542500

loyatemu wrote: »

Times report on the tunnel option:
https://www.irishtimes.com/news/ireland/irish-news/details-of-new-road-tunnel-at-glen-of-the-downs-released-1.4542500

Is there anything suggesting that the Red route definitely involves widen the existing road through the GOTD? Articles based on presumption rather than fact seems to be standard for the IT.

If I have this right, the purpose of this upgrade is to add a 3rd lane, whether that be a bus lane or for general traffic. I can't think of anywhere where we current have a 3 lane tunnel. Port tunnel, Limerick, Jack Lynch all 2 lanes. Even tunnels I remember from the UK are only 2 lane. From a safety point of view, would a 3 lane tunnel be problematic. Just wonder is this tunnel idea really a runner at all.
I'd prefer they put a tbm under Bray head to increase the train capacity if they're going to all that trouble tbh.

prunudo wrote: »

If I have this right, the purpose of this upgrade is to add a 3rd lane, whether that be a bus lane or for general traffic. I can't think of anywhere where we current have a 3 lane tunnel. Port tunnel, Limerick, Jack Lynch all 2 lanes. Even tunnels I remember from the UK are only 2 lane. From a safety point of view, would a 3 lane tunnel be problematic. Just wonder is this tunnel idea really a runner at all.
I'd prefer they put a tbm under Bray head to increase the train capacity if they're going to all that trouble tbh.

The purpose of the upgrade is to improve safety and reduce congestion - whether that is best achieved by adding a third lane, a bus lane, closing junctions, new offline motorway section or something else is what ARUP are currently in process of deciding.

This is why I am skeptical they will make significant improvements north and south of the Glen, and leave the SAC section as is. I think that would be very hard to argue that they have achieved the objective of the scheme given the Glen is biggest cause of collisions and congestion.

A two lane tunnel can achieve this objective if it is free flowing.

Chris_5339762

Wonder could they combine things a bit... send southbound traffic through a 3 laned Glen, then northbound goes through the new tunnel.

schmittel wrote: »

The purpose of the upgrade is to improve safety and reduce congestion - whether that is best achieved by adding a third lane, a bus lane, closing junctions, new offline motorway section or something else is what ARUP are currently in process of deciding.

This is why I am skeptical they will make significant improvements north and south of the Glen, and leave the SAC section as is. I think that would be very hard to argue that they have achieved the objective of the scheme given the Glen is biggest cause of collisions and congestion.

A two lane tunnel can achieve this objective if it is free flowing.

Is the Glen is biggest cause of collisions and congestion? I'm not sure how that can be the case given it has relatively few access points and huge volumes of traffic join the N11 further north. If the accesses on that section were closed, which could be done quite easily, it would probably be the best section of N11 north of CC.

The issue with the N11 is always going to be the limited capacity for cars north of Bray. Adding lanes further south is only widening the mouth of the funnel but with the narrow end staying the same, there is no improvement. If anything, additional lanes will only attract more traffic.

People need to stop thinking in terms of motorway standard being extended north, that isn't the goal here.

Pete_Cavan wrote: »

Is the Glen is biggest cause of collisions and congestion? I'm not sure how that can be the case given it has relatively few access points and huge volumes of traffic join the N11 further north.

Yes according to the Road Safety Impact Assessment. It specifically identifies the Glen as having “a number of significant road safety issues are present along this section of the route”:

The section of the N11 through the Glen of the Downs experiences collisions above the national average rate, with the number rising to twice above the national average rate at junction 10 and its approaches

Macy0161

I do wonder how many of those collisions are at speed, or are fender benders by people not concentrating in traffic (on their phones)/ not copping the end of the queue from Kilmac?

Yeah, if a couple of access points were closed, the GOTD section becomes essentially 2+2 standard. The problem then is too much traffic but the solution to that is providing alternatives, not encouraging even more traffic. Providing more northbound lanes is only going to deliver more traffic quicker to the chronic congestion further north, but with nothing done to relieve that congestion.

Macy0161 wrote: »

I do wonder how many of those collisions are at speed, or are fender benders by people not concentrating in traffic (on their phones)/ not copping the end of the queue from Kilmac?

this is just anecdotal, but the road through the Glen was resurfaced a couple of years ago and there was a ton of complaints on the local FB groups after that the new surface was very slippy when wet, cars skidding etc.

Also as previously discussed, there are a lot of on/offs between J9 and J12, particularly northbound.