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

Typewriter · 23-02-2012 11:43pm

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:

BluntGuy · 24-02-2012 12:02am

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?

Hogzy · 24-02-2012 12:29am

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.

AugustusMinimus · 24-02-2012 12:36am

Borderline insane.

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

Hogzy · 24-02-2012 12:38am

AugustusMinimus wrote: »

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.

AugustusMinimus · 24-02-2012 1:03am

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.

Hogzy · 24-02-2012 1:05am

AugustusMinimus wrote: »

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.

hans aus dtschl · 24-02-2012 11:19am

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.

BluntGuy · 24-02-2012 11:22am

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.

hans aus dtschl · 24-02-2012 11:40am

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.

Hogzy · 24-02-2012 12:02pm

hans aus dtschl wrote: »

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).

Irish and Proud · 24-02-2012 2:05pm

Typewriter wrote: »

All looks good except north to west.

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?

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!

Aidan1 · 24-02-2012 2:20pm

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?

munchkin_utd · 24-02-2012 2:39pm

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.

hans aus dtschl · 24-02-2012 3:29pm

munchkin_utd wrote: »

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.

hans aus dtschl · 24-02-2012 3:33pm

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.

hans aus dtschl · 24-02-2012 3:45pm

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.

munchkin_utd · 24-02-2012 4:03pm

hans aus dtschl wrote: »

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)

hans aus dtschl · 24-02-2012 4:55pm

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?

Hogzy · 24-02-2012 5:06pm

hans aus dtschl wrote: »

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.

hans aus dtschl · 24-02-2012 6:38pm

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?

spacetweek · 24-02-2012 6:51pm

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.

AugustusMinimus · 24-02-2012 9:46pm

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.

Hogzy · 24-02-2012 9:56pm

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.

L1011 · 25-02-2012 12:13pm

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.

SeanW · 25-02-2012 2:28pm

Typewriter wrote: »

All looks good except north to west.

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)

Victor · 25-02-2012 9:19pm

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?

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.

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

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

Hogzy · 25-02-2012 9:38pm

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.

niloc1951 · 25-02-2012 9:42pm

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

Victor · 25-02-2012 9:59pm

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?

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

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