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

munchkin_utd wrote: »

you got me thinking of just how much has already been achieved....

At the moment from the end of the Ballincollig By-Pass to north of Ballymena half ways to Coleraine theres a continuous stretch of 492km of motorway and Dual Carraigeway with only Dunkettle and Newlands cross being potential sources of delays!
http://goo.gl/maps/AOcs3

Afraid not Hillsborough Roundabout and the disgraceful mess that is Sprucefield knock that one!

Ballincollig bypass to Hillsborough will be DC/motorway once Newlands and Dunkettle are both done.

MYOB wrote: »

And at least 4 roundabouts in the north

I didnt say free flow, just dual carraigeway.
Roundabouts and even the odd traffic light is grand so long as it doesnt cause bad delays as the main thing is that your journey isnt made hell by yaris or underpowered (cheap to tax) pre 2008 saloons like say going from Cork to Sligo, as on a dual carraigeway you can overtake them.
Well, the ones that arent sitting in the overtaking lane the whole time anyhow.

Any ideas on when this scheme may commence or how long the build might take ?

Wonder will they redesignate the Glanmire bypass as the M40 ?

Colm R wrote: »

As for construction starting, I suspect there is too much building as it is on the N40, so finances aside, after the Bandon and Sarsfield road roundabout are completed.

The Bandon and Sarsfield Road roundabouts will be completed in the next few months. Even if they decided to give the go ahead to build this today with the required tendering and detailed design process they'd be doing well to get started by Christmas. I'd be impressed given the current finances if there were diggers on the ground here by the end of 2014.

Alan Healy ‏@alanhealy 54m

The NRA has begun acquiring the necessary lands from 20 property owners to upgrade the Dunkettle Interchange.



Looks a bit messy coming from the tunnel going to M8.

I cant see how you get from m8 coming from dublin into the city centre.

vince wrote: »

I cant see how you get from m8 coming from dublin into the city centre.

You'll have to use the dumbbell to the right of this render.

AugustusMinimus wrote: »

I was initially very much against the M8 to Lower Glanmire Road movement.

However, in the grand scheme of things, this movement will probably take up less than 10% of the total movements at this junction. The dumbbell which this movement will entail will be perfectly capable of taking the traffic load for this movement even at rush hour I suspect.

Considering this is the only mainline movements which will be required to go through the dumbbell, that's not bad at all.


In the grand scheme of things though, the Kinsale Roundabout should have had this treatment done also. There was plenty of room out there to do a slip road style setup which would have sorted a lot of problems. As it is, the queue down airport hill can be terrible at rush hour

The light sequencing is terrible at the Kinsale Roundabout. The green from both the airport hill and grange road doesn't necessarily coincide with a green to get onto the roundabout. Then there is only a 4 car turn at the light to get onto the roundabout. So traffic is just being put into a holding pattern between the two lights (Grange rd, and roundabout).

I can see where they are coming from, as it's clearly to prevent traffic backing up onto the N40 in either direction but it really is a mess.

The first thing I'd do, however, would be to make the exit for Old Kinsale Road to be exit only. Traffic trying to push across 4 lanes here and get to the N40 West causes a lot of problems at any time of the day, and is downright dangerous as they regularly
1. Get into the N40 East only lane and force their way around the roundabout in the outside lane (I get cut off on my way to Frankfield all the time), then
2. Stop dead in that lane trying to force there way across the airport lanes to get to N40 West

It's incredibly frustrating and if it's a truck/bus pulling this stunt the roundabout can get clogged even with low traffic volumes.

It's not outlandish for traffic to head towards the P&R and join the south link to access the roundabout. I do this myself to get to Grange Rd, regularly, as trying to push across 4 lanes of the roundabout is tricky unless its quiet and you can time it between light changes.

They also, I would imagine, want to leave the Lower Glanmire Road for traffic coming from the east, and encourage traffic going down the M8 continue along the South Ring and access via the N27.

Edit: My design was still far, far better though.

Junction Movements

cargo wrote: »

Is the fact that you need to go through 2 RA's to get from M8 to City not going to be a huge drawback to those designs? I'm not from the area but I do travel through this junction from time to time and its normally this movement I take. Or am I just overly worrying. Will this detour be fine once all the other traffic is taken off this movement?Will these RA's have slip for left turns at least?

I wouldn't worry too much. All of the other mainline movements will be done via slip roads.

The only mainline movement not being done by slip road is the M8 to Lower Glanmire Road. The way I think about it, is those 2 roundabouts are facilitate that one movement and exit and entry to and from Glounthaune and Little island.

Traffic going into and out of Glounthaune and Little Island won't be big. For the most part, people going from M8 to Lower Glanmire Road won't have to stop very often at those roundabouts as traffic on them will be so low. Even at rush hour I suspect.

The more I look at their design, the more that the M8S - N25W (Dublin to Cork) movement is irritating me. A simple third level on the design and they could plop this movement in. Whether they are trying to keep the whole thing to two levels I'm not sure but looking at it, there is plenty of room. It really is beginning to seem to me to be a very stupid idea.

AugustusMinimus wrote: »

IMO, they clearly do not want traffic entering into the city via the South Link. Would cause excessive traffic at both the Kinsale Roundabout and the end of the South Link Road at Eglington Street.

As others have said, an extra grade separation may have increased costs dramatically. The way I view the junction is that there are 12 main movements and a number of other movements in regards to Little Island and Glounthaune.

Of the 12 main movements, 11 will freeflow. So 1/12 main movements will have to go through both roundabouts. In addition, another 1/12 may use the roundabouts to access Little Island and Glounthaune.

All in all, I would think about 10% of the traffic will be using those roundabouts. Even at peak traffic, I doubt there will be more than 3 or 4 cars queueing at each one.

If a the commuter populations develop further in the Watergrasshill/Rathcormac/Fermoy area and the two roundabouts do cause issues during morning peak time then the residents of Sallybrook and Glanmire better get ready deal with their villages becoming part of a 'rat-run'

phatmanwc wrote: »

the M8-Lower Glanmire Road movement will have priority over these movements on both roundabouts, and shouldn't be affected by them.

This is the key point. M8 to Lower Glanmire has priority over all others movements at the roundabouts and so traffic should still flow well through them.

On this basis, I really don't think there should be an issue here. I'd imagine the junction was designed to ensure this movement was given priority on both roundabouts.

Considering irish ten year paper is <2.5% today,
its hard to see how a ppp could provide better value for money.

Anyone hoping for funding to be announced today. It is by far the most needed project in Cork and I would think it also has the highest payoff/cost ratio of any project currently on the table. Its relatively low cost is also an attraction.

niloc1951 wrote: »

If a the commuter populations develop further in the Watergrasshill/Rathcormac/Fermoy area and the two roundabouts do cause issues during morning peak time then the residents of Sallybrook and Glanmire better get ready deal with their villages becoming part of a 'rat-run'

Just posting to update this thread to say that it appears that tailbacks on the M8 and N25 have caused people to use alternative routes. Over the past 2-4 months the "rat-run" through Glanmire (and though we didn't predict it on here, Glounthaune) now sees long tailbacks each morning.

The longest tailbacks at the interchange itself appear to be M8-Tunnel, N25-Tunnel (from East and West), Tunnel-N25 (Mostly Eastbound) and at the N25-Little Island interchange.

The N25-Little Island interchange has been backing up for a few km at peak hours. I really can't see how the current Little Island traffic and Dublin-Cork traffic can coexist at this junction, especially when the Tunnel traffic will free-flow to the junction.

On the face of it, it looks like the proposed design will just move the existing traffic jams to a few km East of their current location.