Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie
Hi all! We have been experiencing an issue on site where threads have been missing the latest postings. The platform host Vanilla are working on this issue. A workaround that has been used by some is to navigate back from 1 to 10+ pages to re-sync the thread and this will then show the latest posts. Thanks, Mike.
Hi there,
There is an issue with role permissions that is being worked on at the moment.
If you are having trouble with access or permissions on regional forums please post here to get access: https://www.boards.ie/discussion/2058365403/you-do-not-have-permission-for-that#latest

N8/N25/N40 - Dunkettle Interchange [open to traffic]

1356787

Comments

  • Moderators, Science, Health & Environment Moderators Posts: 5,144 Mod ✭✭✭✭spacetweek


    It's a good point. I never thought there would be room there so I left it out of my original drawings on the Cork forum, but I was planning something similar to the brown option. Now that I look at it, it might be better to reverse them. Take the blue lanes off closer to the tunnel, have the red lanes cross above them a second time and merge with the N8 northbound more or less under the existing bridges.
    Absolutely - you will defo need this amendment if you are not to have dangerous weaving movements.


  • Registered Users, Registered Users 2 Posts: 6,660 ✭✭✭Blitzkrieger


    I said I'd give this one more go and see if I could make it any simpler, and I think I have with a new layout for the Dublin-Cork City/Dublin-Waterford roads. I tried to make some better drawings using Gimp, but failed miserably, so there's some paint ones below.

    As before, the big considerations here are space, cost and space. I said space twice because it'd be so easy to do a simpler layout if there was more space for development. Also as before, I realise that I'm not really qualified to make good decisions on what land is suitable for building on or what traffic volumes are, but the council called for opinions, so these are mine.

    I'm also acknowledging that when you add in junctions for Glanmire East and Little Island West, you're talking about a 6-way junction here, so that's going to add complexity and cost.

    Here's some overviews :

    182844.JPG
    182848.jpg

    Phase 1.

    Phase 1 would begin the same as before; with re-opening that old section of road next to the train tracks all the way to Glanmire East. If we built a new on-ramp to the M8 from this road, and moved and/or reshaped the Glanmire East roundabout, we could take Cork City-Dublin and Cork City-Glanmire East traffic off the roundabout, with the minimum of cost and disruption. I've drawn this as a two lane on-ramp to the M8, but depending on cost and predicted traffic volumes, it could be scaled back to one lane.

    Work could also be done concurrently on a new ramp to bring traffic from the tunnel northbound to the city. This would begin as soon as possible on the exit from the tunnel and end as close as possible to the bridge over the railway. This would be a one lane ramp to simplify merging with the N25 and make things safer. This land is quite marshy, but some of the official proposals show building here, so I presume it is possible.

    I'd also build a new ramp south-east of the tunnel to take traffic from the N25 westbound into the tunnel southbound. This would go to the left of the existing ramp to the tunnel roundabout and merge with southbound traffic as close to the tunnel as possible. Because of traffic volumes, I think this has to be two lanes, despite the difficulty of merging them safely in such a short space. This also necessitates the closing of the access to Little Island West near the tunnel. Depending on the duration of works, hopefully it wouldn't inconvenience drivers for too long. We can also lose the roundabout at Little Island West now.

    182845.JPG
    Phase 2.

    Phase 2 is simply a new ramp to take traffic out of the tunnel northbound to the N25 eastbound. To accommodate traffic during construction could be tricky, but on completion it will begin just past the existing bridges, loop up over the M8, stay up, and merge with the N25 more or less where it does now. I wouldn't have thought there was space for it, but the red option has something similar. This is two lanes due to traffic volumes, though would probably start as one.

    182846.JPG
    Phase 3.

    Phase 3 is the heart of this design. In phase 3 we build a big new ramp to take traffic from the M8 southbound both east and west. We do this by bringing traffic from under the existing overpass up over our new tunnel access ramp and to the east. To the east this then splits so that traffic can join the N25 westbound before the existing flyover, and the N25 eastbound after the existing Glanmire East on-ramp. This is two lanes and would in the future be a vital traffic artery. Not only would this carry Dublin to Cork City traffic, but in the future Shannon to Rosslare traffic is planned to go north of the city and join the M8 southbound. This would be a very expensive ramp but it's importance cannot be underestimated.

    This ramp has itself got an on-ramp and off-ramp for Little Island west. One to take traffic to Little Island west starts just east of the existing road, and one west of the existing road to bring traffic from Little Island onto the ramp and then to the N25 east or west. I've drawn these as pretty small but they would probably have to be bigger. These could also be on the other side of the ramp to create more space, but would then be merging with traffic from the right.

    I'd also build a new ramp at this point to bring traffic from the N25 westbound to the M8 northbound during phase 3. This begins just past the existing flyover and loops down to join the M8 northbound just before the bridges. I believe the brown option has something similar. I think this would have to be one lane due to safety concerns, though as stated above, this would also have to carry Rosslare to Shannon traffic.

    The last major ramp built in this phase is to take traffic from the city to the tunnel southbound (and Little Island). This starts just past the bridge under the M8 on the old road, goes up over the railroad tracks and joins the M8 southbound before the bridges. There's also a ramp from the yellow ramp from phase 2 which joins this ramp, to accommodate traffic from the tunnel northbound that wishes to go to Little Island west.

    At this point we'd also start 'straightening' the tunnel roundabout so that it's basically two lanes straight through, with on-ramps and off-ramps on the left of each dual carraigeway. I didn't draw this because my crappy drawing is probably busy enough. :o

    182847.JPG
    Phase 4

    Phase 4, apart from sealing off the roundabout, is really just a minor and optional thing. In these plans there's no provision made for traffic from the M8 southbound to Glanmire East. I'm not sure what the volumes are, but if you didn't want to send this traffic through Glanmire or to the Little Island junction, you could build the green ramp shown to take traffic from the red ramp to the existing Glanmire east ramp.


    And that's it. If you're wondering how you get from the N25 westbound to Glanmire east, you take the red ramp to the M8 northbound, then the yellow ramp to the existing Glanmire east access road. It's not great, but atm you have to go all the way around the roundabout, so with the new free flow system it'd probably take around the same time.

    To get from the tunnel northbound to Little Island west is a bit complicated too. You have to take the yellow ramp, then the turn down onto the read ramp north of the interchange. You then turn off before the tunnel as before onto the main red ramp, and turn off that down onto the existing road. It'd probably take a bit longer than it does at the moment, but shouldn't make a massive difference if you count the time waiting at traffic lights.

    So there you have it. With proper project planning delays could hopefully be kept to a minimum. A lot of what I've set out as separate phases could actually be built concurrently with a view to keeping road closures to a minimum.
    .
    The Glanmire roundabout I'd treat as a separate project. I may do a post on that in the next few days. I misread the bit about the 'new Little Island Interchange' before too, but there's traffic problems with the N25/Little Island junction too so I may do a post on that too.


  • Registered Users Posts: 761 ✭✭✭Jayuu


    Great post Blitzkreiger but it looks like a lot of work to make the junction freeflow.

    I'm just wondering if the M8/Tunnel flow was taken off the roundabout and four filter lanes put in place to take left bound traffic off the roundabout (e.g. City Centre > M8 North / M8 South > N25 East / N25 West > Tunnel / Tunnel > City Centre) that would only leave cross flow traffic using the roundabout. Would this be enough of a solution to make the roundabout usable.

    It seems like a smaller more easily implemented solution. The question is would the roundabout still be too full to cope?


  • Registered Users, Registered Users 2 Posts: 6,660 ✭✭✭Blitzkrieger


    I agree. In the current economic climate I'd love to do it as cheaply as possible, but doing half a job could cost more in the long term, and I'd be worried about traffic volumes in the future.
    Jayuu wrote: »
    / N25 West > Tunnel /

    If you look at the first picture in my first post above, I think a lot of what you propose is covered by the blue roads. The problem is, how do you propose to get traffic from the city to the tunnel southbound? It's the toughest road to situate.

    I think you're also understimating the volumes involved in the clash between traffic out of the tunnel nortbound going either to Little Island or the N25 eastbound, and traffic on the M8 southbound to the tunnel and the city. I don't have data but from observation this seems to be the biggest traffic issue in the junction to me.

    Your solution may also not be future proof - what about traffic from the N25 westbound to the M8 northbound? It's probably not a huge volume now, but in the future the proposed Rosslare-Shannon motorway is to go north of the city, so that traffic will also have to use this junction.


  • Registered Users Posts: 761 ✭✭✭Jayuu


    I agree. In the current economic climate I'd love to do it as cheaply as possible, but doing half a job could cost more in the long term, and I'd be worried about traffic volumes in the future.



    If you look at the first picture in my first post above, I think a lot of what you propose is covered by the blue roads. The problem is, how do you propose to get traffic from the city to the tunnel southbound? It's the toughest road to situate.

    I think you're also understimating the volumes involved in the clash between traffic out of the tunnel nortbound going either to Little Island or the N25 eastbound, and traffic on the M8 southbound to the tunnel and the city. I don't have data but from observation this seems to be the biggest traffic issue in the junction to me.

    Your solution may also not be future proof - what about traffic from the N25 westbound to the M8 northbound? It's probably not a huge volume now, but in the future the proposed Rosslare-Shannon motorway is to go north of the city, so that traffic will also have to use this junction.

    I know its not the long-term or full solution and something along the lines of what you are proposing, making the entire junction freeflow, is better.

    However in the current economic climate its a solution that might be implemented to alleviate some of the disruption. Clearly it would have to be future-proofed so any sliproads built would have to be capable of being used in a full development scenario at a later date.

    But if even the M8/Tunnel flow and all left bound traffic was taken off the roundabout via slip roads or overpasses then at least the roundabout wouldn't be as big a congestion point as it currently is. I think its a feasible solution for the shorter term providing the future proofing was considered.


  • Registered Users, Registered Users 2 Posts: 78,490 ✭✭✭✭Victor


    I think you'd be surprised how much some free-flow left turns would improve things, not so much in the amount of traffic taken off, but show much less interaction there would be.

    Certainly, removing the city-Fermoy/Glounthaune traffic would make a big change, although it is likely to be the most expensive to do.

    A straightforward left turn from Little Island to the tunnel might be difficult, due to the off ramp from the tunnel appraoch.

    I can't see the M8-tunnel vertical alignment being changed - it is already very steep.


  • Registered Users, Registered Users 2 Posts: 6,660 ✭✭✭Blitzkrieger


    Victor wrote: »

    Certainly, removing the city-Fermoy/Glounthaune traffic would make a big change, although it is likely to be the most expensive to do.

    This is where my lack of knowledge of road building comes in - I would have thought that would be the cheapest part of the plan. I don't see how it would take that much work to re-open the old road to Glounthaune, and I'd have thought it'd be relatively simple to build a ramp from the old road onto the M8 northbound?

    The absolute cheapest, far from ideal and most future proof solution I can think of would have the above as part of the solution. Scaling back from my latest set of drawings, if you re-opened the old Glounthaune road in blue, built the yellow flyover and the red ramps north east of the junction I think you could make a vast improvement.

    The yellow flyover is proposed in some of the official plans and I think would give the most bang for buck. By including the red ramps too, you can close off the west-east section on the north of the roundabout. Traffic from the city to the tunnel would use the blue road then the red ramp. Traffic from the tunnel to Little Island would use the yellow flyover then the red ramp. Just doing this would massively improve traffic flow. I say "just" - it wouldn't be cheap by any stretch of the imagination.


    I'd be nice to simplify the junction further by closing off the east-west section south of the roundabout too. If you force N25 westbound to M8 northbound traffic to continue on to the Dunkettle roundabout, turn around and use the blue ramp onto the M8, and force Little Island west to city traffic to use the other Little Island exit, you could do this simply. You'd effectively be left with no roundabout - just a north/south dual carriageway, but you'd probably have to retain the traffic lights to manage the clash between N25 westbound to tunnel and M8 southbound to tunnel traffic. Not underestimating the impact that this would have on Little Island traffic, this would make traffic out of the tunnel northbound completely free flow.


  • Registered Users, Registered Users 2 Posts: 78,490 ✭✭✭✭Victor


    This is where my lack of knowledge of road building comes in - I would have thought that would be the cheapest part of the plan. I don't see how it would take that much work to re-open the old road to Glounthaune, and I'd have thought it'd be relatively simple to build a ramp from the old road onto the M8 northbound?
    Sorry, I meant the most expensive of the four left turns.

    To restore the Cork-Glounthaune road would mean putting bridge under the Glanmire Bypass.

    I think it would be impractical for the limes of HGVs to manage the steepness of going from the Cork-Glounthaune road to the Glanmire Bypass - the bypass itself is already steep enough. This likely means putting a bridge on the slip road as well.


  • Registered Users, Registered Users 2 Posts: 6,660 ✭✭✭Blitzkrieger


    I honestly can't remember if there's already a bridge on the old Glaunthaune road under the M8. I thought there was. If not, that would add considerable expense to opening that road.

    I don't think a slip road from that road to the M8 would add much steepness. I doubt if there's much difference in elevation from there and from the tunnel interchange. I'm guessing it'd be a long enough slip road anyway.


  • Banned (with Prison Access) Posts: 8,632 ✭✭✭darkman2


    Any news on this? I thought a preferred option was to be published long before now:confused:


  • Advertisement
  • Registered Users, Registered Users 2 Posts: 797 ✭✭✭mydiscworld


    darkman2 wrote: »
    Any news on this? I thought a preferred option was to be published long before now:confused:

    Well the website hasn't been updated in ages

    http://www.n8n25dunkettle.ie/programme.html


  • Closed Accounts Posts: 1,735 ✭✭✭Irish and Proud


    darkman2 wrote: »
    Any news on this? I thought a preferred option was to be published long before now:confused:

    Here's something (dated 7th Nov 2011) I just came across by chance!

    Unfortunately, I can't find any further update - maybe the process is taking longer than anticipated or the Budget 2012 killed the scheme off - let's hope it's the former!

    Regards!


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    Jacobs are unveiling the tunnel in the Radisson, little island, from 13.00 to 20.00 today, with an open seminar.

    I just received a letter about this.

    I hope to go and ask about myriad of idiot-inspired plans in the design: the lack of a direct Dublin-Cork City route, lack of proper cycle route from East to West etc.


  • Banned (with Prison Access) Posts: 8,632 ✭✭✭darkman2




  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    Thanks Darkman - a little rushed there I forgot the link.
    I obviously meant to type the "tunnel interchange" rather than just "the tunnel" too.


  • Registered Users Posts: 260 ✭✭csd


    Am I reading this correctly? Does Dublin - Cork traffic have to go through the two roundabouts of a dumbell interchange?!


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    csd wrote: »
    Am I reading this correctly? Does Dublin - Cork traffic have to go through the two roundabouts of a dumbell interchange?!

    Yes. Its stupid. I can only imagine how congested those roundabouts will be.


  • Registered Users Posts: 799 ✭✭✭Poulgorm


    The Dunkettle interchange, no matter how you modify it, will never work properly. It is simply too close to the sub-sea entrance to the tunnel.

    The M25 flyover is a disaster - one of the proposals at the time was for a cable stayed bridge, which would not have had supports, blocking the middle of the roundabout. But of course, it was turned down - by the same short-sighted people who scrapped the planned flyovers at the Kinsale road roundabout, as well as Sarsfields and Bandon Road roundabouts - the cost of construction these now has dwarfed the cost of building them the first day.

    The N25 flyover at Dunkettle needs to be replaced with a single span cable-stayed bridge. The traffic to & from the tunnel could then run straight through northwards / southwards, with a proper grade separated junction between the M8 and M25, located to the north, where there is more space.

    It would have to all worked out, but moving the junction northwards is the only real solution I can see.


  • Registered Users, Registered Users 2 Posts: 69,542 ✭✭✭✭L1011


    Where can you make representations about that layout? As I imagine it'd be worse than the current one.


  • Advertisement
  • Closed Accounts Posts: 1,735 ✭✭✭Irish and Proud


    darkman2 wrote: »

    The preferred option seems to be a combination of the Red and Brown options with the direct movement for the M8 South to N8 City omitted. I guess the engineers don't want too much traffic heading into Cork via the Tivoli Underpass - that road is pretty tight from after Tivoli with just 2 lanes - wasn't there a plan way back in the 1980's to upgrade the N8 between Tivoli and the City Centre to DC? I remember hearing about a such a road in Cork being scrapped then - there also happens to be plenty of space under the Tivoli Flyover for a DC.

    Regards!


  • Registered Users Posts: 577 ✭✭✭Typewriter


    All looks good except north to west.

    picture.php?albumid=378&pictureid=12058

    I can see the point of discouraging traffic heading into the City from this direction. IMO all city bound traffic should be directed via the N27. But as long as people still live on the north side of the city it does not and will not make any sense until the northern ring road is built.

    Actually if the eastern gateway bridge, from Tivoli to south docklands is ever built it won’t make sense then either.
    Maybe this is all a ruse so it gets stuck in the appeal process for years and never gets built. :cool:


  • Closed Accounts Posts: 2,468 ✭✭✭BluntGuy


    In my opinion that movement you've highlighted is going to cause a lot of congestion.

    I appreciate they've a difficult task to do, but I'd consider that one of the more important movements that needs free flow.

    Do they have any document outlining their rationale?


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    BluntGuy wrote: »
    In my opinion that movement you've highlighted is going to cause a lot of congestion.

    I appreciate they've a difficult task to do, but I'd consider that one of the more important movements that needs free flow.

    Do they have any document outlining their rationale?

    Exactly. There is a large amount of commuting traffic coming from Fermoy, Watergrasshill etc. Tailbacks can reach up to 2 miles long at times. Putting that traffic through 2 roundabouts is a disaster in the making. Granted some of it goes to little island and the south side via the tunnel but I would imagine the majority of it is going into the city (where the majority of people work.).

    Those roundabouts are going to get clogged really quickly.


  • Registered Users, Registered Users 2 Posts: 4,561 ✭✭✭AugustusMinimus


    Borderline insane.

    Half of the traffic will go through Glanmire instead clogging the place up again.


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    Borderline insane.

    Half of the traffic will go through Glanmire instead clogging the place up again.

    They probably wont to be honest. Why would you go through an entire town to avoid 2 roundabouts.


  • Advertisement
  • Registered Users, Registered Users 2 Posts: 4,561 ✭✭✭AugustusMinimus


    Hogzy wrote: »
    They probably wont to be honest. Why would you go through an entire town to avoid 2 roundabouts.

    Because the tailback at those roundabouts could be worse than going through Glanmire.


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    Because the tailback at those roundabouts could be worse than going through Glanmire.

    It wont be that bad. It wont be worse than what Dunkettle is at now. Traffic levels arent increasing.


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    Never had the chance to go to the radisson, yesterday.

    I can see a lot of the Dublin traffic destined for Mayfield/Tivoli/Lovers Walk (and of course industrial traffic of the Port of Cork) choosing to travel through Glanmire at peak hours rather than using the same miniature roundabout as the City-LI, Dublin-LI and Glanmire-LI traffic.

    Also, unless I'm mistaken, Dublin traffic to the east (Midleton/Waterford) either has to go through the same miniature roundabout or cross over a slip road á la Bloomfield Interchange.

    It's almost as though they forgot this was the primary route from the rest of the country to Cork.


  • Closed Accounts Posts: 2,468 ✭✭✭BluntGuy


    Hogzy wrote:
    Those roundabouts are going to get clogged really quickly.

    I fear so too, in fact looking at the movements, I'm just not seeing how a dumbbell can cater for all of them at peak times. There seem to be no other documents attached explaining why this design was chosen. It feels like the one big problem that the upgrade should be solving, isn't being solved.


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    The movements list shows that the following all go through the same miniature roundabout:

    South-LI
    South-Glounthaune
    North-West
    North - LI
    North - Glounthaune
    Glounthaune - South
    Glounthaune - North
    Glounthaune - West
    Glounthaune - East
    Glounthaune - LI

    So in fact, of the 30 movements, 10 of them, or some 33% go through one miniature roundabout.

    The same one the pedestrians and cyclists are expected to navigate, incidentally.

    Genius.

    The same amount (10) that go through the tunnel itself. I know usage numbers are the only important aspect, but it seems a lot of different routes are expected to use one small roundabout, critically including the North-West traffic.
    Recipe for disaster.
    Or more likely just getting traffic back into Glanmire.


  • Advertisement
  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    The movements list shows that the following all go through the same miniature roundabout:

    South-LI
    South-Glounthaune
    North-West
    North - LI
    North - Glounthaune
    Glounthaune - South
    Glounthaune - North
    Glounthaune - West
    Glounthaune - East
    Glounthaune - LI

    So in fact, of the 30 movements, 10 of them, or some 33% go through one miniature roundabout.

    The same one the pedestrians and cyclists are expected to navigate, incidentally.

    Genius.

    The same amount (10) that go through the tunnel itself. I know usage numbers are the only important aspect, but it seems a lot of different routes are expected to use one small roundabout, critically including the North-West traffic.
    Recipe for disaster.
    Or more likely just getting traffic back into Glanmire.

    To Be fair most of the South to Little Island traffic will probably just go to the second exit for little Island (near KFC).


  • Closed Accounts Posts: 1,735 ✭✭✭Irish and Proud


    Typewriter wrote: »
    All looks good except north to west.

    picture.php?albumid=378&pictureid=12058

    I can see the point of discouraging traffic heading into the City from this direction. IMO all city bound traffic should be directed via the N27. But as long as people still live on the north side of the city it does not and will not make any sense until the northern ring road is built.

    Actually if the eastern gateway bridge, from Tivoli to south docklands is ever built it won’t make sense then either.
    Maybe this is all a ruse so it gets stuck in the appeal process for years and never gets built. :cool:

    Good points mate! ;)

    I am definitely having second thoughts about the omission of a direct M8 South to N8 City Connector - to add to your points, I would also be concerned that if something happened to the tunnel, where would all the traffic go? :confused: As other posters pointed out, the dumbell would probably become overburdened thereby resulting in Glanmire becoming a rat run during peak times to say the least. I'd say to Jacobs etc:

    "No, you must include that connector - to do otherwise would be a very big mistake - I'm broadly happy with rest of the proposal - there is a weaving movement on the M8 South to N25 East connector - it might be OK though - time will tell."

    I'm also wondering if anyone at the helm is considering extra capacity for the tunnel itself - isn't traffic something like 60,000 PCUs/day there - the M50 was in big trouble when there was 80,000 to 90,000 PCUs/day trying to fit into 2 lanes each way - if the economy takes off again, it might not be all that long till those numbers are reached in the Jack Lynch Tunnel - I think that starting the planning process for same should be considered, especially if the CNRR is not to be built in its entirety.

    Regards!


  • Closed Accounts Posts: 624 ✭✭✭Aidan1


    While I agree completely that the North to West movement stands out as a very difficult sell, the only thing in it's favour are the fact that the North Ring Road should take a lot of traffic off that movement in years to come. Problem - it may never get built. Of course, I'm not suggesting that anyone would deliberately engineer in a blockage so as to ensure that a different project would have to be delivered. Oh no. That'd never happen.

    The obvious practical reason for this design is, I assume, to keep costs down (by reducing the number of structures needed). Question to the crayonistas out there; what are your solutions?


  • Registered Users, Registered Users 2 Posts: 7,907 ✭✭✭munchkin_utd


    Aidan1 wrote: »
    The obvious practical reason for this design is, I assume, to keep costs down (by reducing the number of structures needed). Question to the crayonistas out there; what are your solutions?
    the current plan if you look at it has one MASSIVE advantage is that theres minimal disruption during construction.

    The existing east-west N25 flyover toward town remains in situ along with its 2 over bridges and they probably can do the other building work in stages to the side.

    Any plan that requires the flyover to be ripped up or significantly altered means that during construction you have MORE traffic to manage, not less!

    This project is not happening in a green field. Its a junction with 60,000 cars a day on it that will still need to be accommodated during construction.

    I think the current layout is more than adequate:
    - it links North cork and the rest of ireland to the employment centres in Little Island and to the cobh hinterland and beyond with freeflow.
    - It also links the rest of Ireland with the south side of the tunnel by free flow, i.e. West Cork, the airport, Ballincollig etc
    - It also links the residential areas south of the river, i.e. most of the city, suburbia like Ballincollig and Carraigaline with the industrial areas that people goto at rush hour like Little Island.

    What it doesnt do is link north cork/ the rest of Ireland with Mayfield and the north inner city.
    Are there really that many heading to those areas for working?

    My knowledge of Corks Geography is that the main jobs centres are the south inner city, around the south ring (both in retail and industrial estates) and over in little island.
    All those areas would presumably be where the majority of people are going to during rush hour from the Fermoy direction and those flows are freeflow.

    And honestly, the traffic is only really bad during rush hour so this is probably not as big an issue as it superficially seems.


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    What it doesnt do is link north cork/ the rest of Ireland with Mayfield and the north inner city.
    Are there really that many heading to those areas for working?

    My knowledge of Corks Geography is that the main jobs centres are the south inner city, around the south ring (both in retail and industrial estates) and over in little island.

    The entire port of Cork is there, as well as the majority of access to the marina industrial estates of centre park and monaghan roads. And the industrial estates of the upper city centre would be accessed this way also, rather than the Barrnavara route which is too steep/congested for most.

    To those pointing to the fact that the Little Island traffic can access via the primary Little Island entrance, I point to the significant tailbacks on this route at peak times at present which result in tailbacks on the eastward motorway.


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    Hogzy wrote: »
    To Be fair most of the South to Little Island traffic will probably just go to the second exit for little Island (near KFC).


    The main Little Island junction is backed up most mornings due to the traffic lights, and a lot of traffic chooses to use the back road instead.


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    Aidan1 wrote: »
    The obvious practical reason for this design is, I assume, to keep costs down (by reducing the number of structures needed). Question to the crayonistas out there; what are your solutions?

    Well there aren't a lot of easy options, are there?

    The main stumbling blocks at present are in getting the Tunnel traffic north and east, and in getting the northern traffic south and west.

    I don't have any figures whatsoever but I think a direct route from north to south is what is actually needed. Seems like anything else is just faffing about at the edges.


  • Registered Users, Registered Users 2 Posts: 7,907 ✭✭✭munchkin_utd


    To those pointing to the fact that the Little Island traffic can access via the primary Little Island entrance, I point to the significant tailbacks on this route at peak times at present which result in tailbacks on the eastward motorway.
    actually, when you look at it theres a bigger problem

    Traffic from Dublin heading toward Midleton/Little Island must first merge with the traffic from the tunnel heading for Midleton/Little Island (not a big problem).
    Within metres of that happening, you are then getting this traffic splitting for Little Island to the left and Midleton to the right.
    At the same time the Dublin/Tunnel->middleton traffic is attempting to get out onto the N25 they are confronted with traffic coming OFF the N25 trying to cut across their path completely to get up on the ramp to Little Island.

    If there is any blockage on the little island exit roundabout leading to a small tailback towards the mainline then the whole system will break down as Dublin/Tunnel->Midleton traffic will be blocked getting onto the N25 by a queue of traffic coming from town leaving the N25 snaking across their path to Little island.

    Have a look at the diagram again. It doesnt work.
    Two of the main flows, Tunnel->Middleton/Dublin->Middleton are in conflict with Town to Little Island.
    It'll be carnage!
    (A solution to all the criss crossing is to keep tunnel/Dublin-> Midleton traffic to the left and thread them under the roundabout but this isnt in the plan)


  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    You're spot on, Munchkin_kid, I mentioned this yeaterday in my reference to the "bloomfield interchange". Dublin traffic is expected to cross over three lanes in a very short distance essentially.

    I genuinely think this plan does not address the main issue, and somehow manages to build 8 bridges.
    What's needed is a direct route north to south. Is it possible to build a proper north-south interface either below or up above the existing junction?


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    What's needed is a direct route north to south. Is it possible to build a proper north-south interface either below or up above the existing junction?

    Unfortunatly not. The tunnel is too close to the junction. If they were to do that it would have to be at a VERY steep incline. There probably wouldnt be enough room for off ramps coming from the Tunnel and going east or west. Look on Google maps.


  • Advertisement
  • Registered Users, Registered Users 2 Posts: 3,241 ✭✭✭hans aus dtschl


    How about (whisper it) a tunnel beside the existing one for north-south traffic?
    How much would that cost and what would be the traffic impact in comparison to the plan outlined by jacobs?


  • Moderators, Science, Health & Environment Moderators Posts: 5,144 Mod ✭✭✭✭spacetweek


    The M8->Tunnel movement has a tight weaving bit as it passes under the flyover. They had no choice though, but I still agree with the poster that mentioned the cable-stayed bridge. That would have been a lot better. Also this weaving might mean that the south link can't be upgraded to motorway as this weaving route through the junction surely isn't up to motorway standard.

    I also notice that they're reopening the old road, which appears as a laneway on aerial maps, the western end of which is closed.

    There's something we haven't considered here. We're saying that the M8->City movement has been omitted but it's OK cause you could use the North Ring Road; in fact, this may very well be the intention. The designers may have been told that the movement would be provided elsewhere.

    Providing the missing movement by adding a loop to the south-east quadrant wouldn't really be possible; it's too close to the tunnel entrance and is probably on a downhill slope. Also it'd have to be too tight, and presumably double-laned : there's no room for that. The only solution would be to construct a huge viaduct leading from the M8 at the Dunkettle Rd overbrige directly to the roundabout at Lota. This would need to overbridge both the mainlines of N8 and M8, and the Dunkettle Road.

    Hans aus dtschl, remember that most of the movements you've listed won't have very high traffic levels. Most of those are very specific. Little Island is just industry and Glounthaune is a small village. However, it is proposed to build a park 'n ride there for the railway. That will presumably go here.

    One renumbering possibility that could be useful is to rename the South City Ring as N8 or M8, and the Dunkettle Junction->City road (currently N8) as a Regional Road. The N25 coming from the east would terminate at the junction.


  • Registered Users, Registered Users 2 Posts: 4,561 ✭✭✭AugustusMinimus


    Are you saying that all the traffic from the N8 to city centre should use the North Ring Road and then join in with N20 traffic along the Blackpool bypass ?

    Would be congestion nightmare.


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    spacetweek wrote: »
    One renumbering possibility that could be useful is to rename the South City Ring as N8 or M8, and the Dunkettle Junction->City road (currently N8) as a Regional Road. The N25 coming from the east would terminate at the junction.

    What would the point of this be? I seriously doubt they will make the N25 a Motorway. There is no hard shoulder in the tunnel or on the Douglas Viaduct. It would be nice though. There are way to many tractors on the bloody road. Its dangerous. Mind you making a road a motorway doesnt stop the tractors coming onto it. Some farmers havnt a clue of the rules of the road.


  • Registered Users, Registered Users 2 Posts: 69,542 ✭✭✭✭L1011


    spacetweek wrote: »
    One renumbering possibility that could be useful is to rename the South City Ring as N8 or M8, and the Dunkettle Junction->City road (currently N8) as a Regional Road. The N25 coming from the east would terminate at the junction.

    We're fairly certain that its being re-numbered N40 based on signs that have already been erected with removable patches.


  • Registered Users, Registered Users 2 Posts: 8,868 ✭✭✭SeanW


    Typewriter wrote: »
    All looks good except north to west.

    picture.php?albumid=378&pictureid=12058
    Good grief! I take it the people who do realise that this is the N8 National Primary Route that they propose to send on such a ridiculous wild goose chase? Conflicting with the pedestrian/cyclist route? And a bunch of other traffic routes? :(

    Would it be possible to amend the plans to add a curved ramp from the route south over to the West? (See attachment)
    194133.PNG


  • Registered Users, Registered Users 2 Posts: 78,490 ✭✭✭✭Victor


    I think getting an accurate count of the individual traffic flows would be important before deciding whether it works or not, but certainly the flow from north to west is strange and confusing. Additionally, the flow from north to east (red) conflicts with the flow from south to Glounthaune / Little Island (dark blue) and that part of the junction risks becoming oversubscribed. I think it may be ambitious for the pink line to go over the red line and under the light green line. Traffic from west to north may find the slope excessive.

    Making more than minor parts of it motorway would create problems - what would mopeds and work vehicles do?

    194188.PNG

    As the southern roundabout at Little Island, things could be simplified by having one less arm on the roundabout (pink arm removed in image below). Note, they don't seem to include the road from this roundabout to the coast road (R623) on Little Island.

    194189.PNG

    You could omit the pink bit completely by forcing that traffic to do a turn as the old Dunkettle Roundabout.

    194190.PNG
    SeanW wrote: »
    Good grief! I take it the people who do realise that this is the N8 National Primary Route that they propose to send on such a ridiculous wild goose chase? Conflicting with the pedestrian/cyclist route? And a bunch of other traffic routes? :(

    Would it be possible to amend the plans to add a curved ramp from the route south over to the West? (See attachment)
    https://us.v-cdn.net/6034073/uploads/attachments/40471/194133.PNG
    Possible, but you would create a conflict between merging and leaving traffic. Also, a lot of traffic wouldn't make it up the curve and people who approach it too fast might find themselves escaping orbit. :eek: http://maps.google.ie/maps?q=Dunkettle,+Cork&hl=en&ll=51.903825,-8.387976&spn=0.013424,0.042272&sll=53.401034,-8.307638&sspn=6.644571,21.643066&oq=dunkett&hnear=Dunkettle,+County+Cork&t=m&z=15&layer=c&cbll=51.903831,-8.387392&panoid=VDezRtcXtUoj0rWn0Te94w&cbp=12,64.76,,0,-8.79


  • Registered Users, Registered Users 2 Posts: 7,544 ✭✭✭Hogzy


    WHy does there HAVE to be access to Glaunthaune from the junction anyway. Surely the Glaunthaune traffic could use the Dunkettle roundabout aswell as that road that "used to be a road".

    This would keep the junction primarily for traffic switching between M8 and N25. It would also get rid of those 2 roundabouts.
    Ill try draw out a map if i have time later.


  • Registered Users, Registered Users 2 Posts: 2,058 ✭✭✭niloc1951


    How to get to Cork City from Dublin.
    .
    .
    .
    .
    .
    .
    .
    At the end of the M8 turn east and leave it behind you
    .
    boom
    .
    boom
    .
    :rolleyes:


  • Advertisement
  • Registered Users, Registered Users 2 Posts: 78,490 ✭✭✭✭Victor


    Hogzy wrote: »
    WHy does there HAVE to be access to Glaunthaune from the junction anyway. Surely the Glaunthaune traffic could use the Dunkettle roundabout aswell as that road that "used to be a road".
    How would they get to the roundabout? Are you suggesting the slip road that goes from the west (Cork) to the north (Dublin) be two-way? That would be a barrel of fun - not.

    How would traffic get from the M8 to Little Island?


Advertisement