N8/N25/N40 - Dunkettle Interchange [under construction]

More visible changes in the last few weeks.

• The M8 South to N25 East slip is now mostly tarmaced. Bridge completed.
• Substantial works done done for the slip tie into the M8.
• The old slip from Glounthaune to M8 South is now open again. Substantial temporary barriers in place.
• Concrete poured on the bridge for the new M8 South mainline. Still need to build up earthworks to match level of bridge on both sides.
• Pillars nearly complete for the 4/4 Dumbell/Bridge east of the current interchange.
• N25 West to M8 North slip is starting to take shape. Significant earthworks completed on it.

They have new metal barriers up on the bridge on the M8 north section by the looks of it.

Assume they’ll move traffic to the east onto the new bridge before long and then dig away the old M8 north section.

That's exactly what I'm expecting also.

And I suspect it will happen soon enough, too, given the looks of that new bridge.

Meanwhile, Cork Co Co has also got approval for a new footpath/cycleway through from Bury's Bridge into the back of Eastgate, with a new dedicated Bus Gate.

So buses will take the Westernmost N25 Little Island slip to access Little Island, via the new Dumbell Interchange. it's not perfect, but it's the most ambitious thing I've ever seen from them

https://www.corkcoco.ie/en/planning/traffic-transport/statutory-processes

This one is by Arup, and I haven't seen a design by them in a while, but I'm fairly sure they've been used before.

It's like someone with a sustainable transport mindset has been magically parachuted in for this one. The bus gates in Eastgate, the removal of the "rat runs" at Harvey Norman, the kerb-separated cycle lanes, the raised table entrance crossings...OK it's not absolutely perfect, but there's some real ingenuity here. I was genuinely shocked at the new sustainable transport entrance to the West of Eastgate.

I still am quite worried about that new Little Island West dumbell interchange though. I may stand corrected, but I just don't think it will cope with the Dublin+Glanmire+Glounthaune+Mahon traffic demands in the mornings. Dublin should be using it to get to Tivoli, Glanmire and Glounthaune using it to get to the tunnel, and Mahon using it to get to Little Island. It just looks like too many flows to me, and the weaving on the northern arm (Dublin+Tivoli) looks very short.

https://www.dunkettle.ie/media/1334/traffic-movements_from-littleisland-glounthane.jpg

Ive always worried about that Little Island "west" junction... for instance will N40E to N25E coming out of the tunnel in the evening get bogged down in traffic trying to join a potential queue up onto that junction. Quite how bad the weaving will be, or how long the merge lanes will be I don't know. None of the models have shown it well enough yet.The trouble is, what other option did they have? The whole interchange itself kind of blocks any attempt at further grade separation.

Where you say "the join between N40/N25E and the N8 North roads will be tapered in such a way that traffic coming from the tunnel will be allowed move right onto N8 North, but traffic that originated from the West has no way to cross over, and must continue onward to N8." that's exactly my concern area. It looks like there are three potential flows joining together at your left-hand pink dot. If that's cut to two, it's much more manageable.

I have secondary concerns about this same junction: Glanmire/Glounthaune traffic will come through it too and I believe it will be quite busy. So I don't think North Cork traffic towards the city is going to choose the M8 when this upgrade is complete, I believe they'll still rat-run through Rathcooney etc. Ultimately, I think when this one's done, we'll still have a North-Cork to City problem.

It's also the active transport route through the interchange! The only improvement I can think of would be an overhead route from M8 southbound through towards the Glashaboy river. It would need two new structures, and the one at the West would be quite complex.

As far as I can tell, the blue coming out of the tunnel will be 2 lanes, right along to C. Orange will be one lane. But I would like to see the proposed lane arrangements for sure, thats the sort of detail we haven't seen just yet.

Of course, it might be somewhat self-sustaining, if traffic is bad at that dumbbell, people might just see it and go along to the Little Island junction.

You've drawn it perfectly and confirmed my thinking also: it's point A to point B in your drawing that I'm most concerned about.

My secondary concern is then the red traffic flow which crosses the bridge over the N25. It's drawn in red on the incorrect side of the bridge but that's immaterial, the point is that it will be Dublin, Cork, Mahon, Glanmire and Glounthaune traffic sharing that bridge lane and I expect it to be quite a heavy flow in the mornings.

Combine these and you get: bridge backed up, slip lane backed up, tunnel backed up.

This is just an observation, I haven't done any mathematics whatsoever and I hope I'm wrong about it!

Chris_5339762, I don't think the tunnel traffic will be able to "see and avoid" if the weaving Dublin-origin traffic clogs point B above: the tunnel will cease to function Eastbound.

I think the only way that this can happen is if traffic is leaving Little Island blocking the upper roundabout, if traffic on the new Little Island link road itself stops, or if there's a crash due to weaving between A and C above.

Great work Kris! You're right, the third lane there will take away a LOT of the problem. I had thought it was two, and that was a major part of my concern!

The busyness of the interchange works is inversely proportional to the busyness of this forum.

I think this also is a facilitator to remove the existing "Ibis" slip road beside M8 Southbound. That slip road needs to be removed reasonably urgently to facilitate other works, so focusing urgency on the movement you've highlighted.

With my "sustainable transport" hat on, it will be an important movement also, as it will be the first cycle route directly into Little Island. It's unlikely this cycle route will get much use in the short term, but in the medium-to-long term, there will be some "on-road greenways" from Glanmire to Dunkettle, and it will be a viable commute for some current drivers. You can imagine, for instance for people in the new Ballinglanna estate, that this will cut 2km or so off their 5km journey. That's a big deal. It will also for the first time facilitate buses into and through Little Island as a viable commuter bus route. There was a proposal also to have a "shuttle" route from the Train Station through the Island and back via this interchange, but I don't see this happening in the short term.

To add to that the entire interchange (apart from the old slip into Glounthaune) is still in-situ. It may be complex now, but when they do the diversions to build the bits on the current footprint of the interchange, it'll be even more complex.

That is the long-term plan, yep. South of the Glashaboy bridge, and South of the Tunnel Management building. The route will be viable but it looks like an opportunity to de-traffic Dunkettle will likely be missed. Obviously very far into the future, but some challenges that will need to be dealt with are:

The route will be on the boundary of the harbour SPA. It will be resisted particularly at the mouth of the Glashaboy River.

The route through Tivoli will be complex: there will be a P&R and it will be a dense urban area. I have low confidence in the ability to deliver a route of quality through that.

In draft Tivoli masterplans to-date there have been a mix of a direct "transport" route and an indirect "scenic" route along the shoreline. Where it's been "direct", it has been a "tag-along" to the primary motorised vehicular access. It's likely that a BOTH a "tag-along" direct route and a "scenic" shoreline route will be delivered, neither of which will work well for transport.

The link eastward from Dunkettle interchange to Little Island is currently of low quality and will need to be upgraded.

Finally, there is a plan to add a new river crossing from Centre Park Road to the Millennium Garden (Tivoli) and I believe that this movement will be a key part of delivery of an East-West corridor. The proposed design of this is a bus corridor with "tag-along" cycle lane to the motorised vehicular access.

From a Dunkettle perspective unless we upskill big time in active transport infrastructure design we're going to struggle to get meaningful modal shift. More cars will certainly come through Dunkettle from Tivoli. Cars, buses and trains. The opportunity is available to create a model "active transport" area but I don't think we'll see that opportunity materialise. At this point it's more likely that we'll get good mass transit in the area.

Sorry for digressing so much, but in fairness it does heavily concern Dunkettle.

I'm expecting the new Little Island West dumbell interchange bridge to start getting its the beams installed before too long.

The upright pillars are all nearing full height by the looks of it.

I was able to have a little more of a look at the new M8 bridges over the railway line, and there's still a good bit to do on both of them from what I can see. There's not enough earthworks on either side and certainly no blacktop on the bridges themselves. So a bit more to go there. The widening of the M8 L2998 bridge is ongoing, but looks like it's well over half-way, to my untrained eye.

Pretty sure I passed two of them on trucks at the site last night. It was a hive of activity around 10pm.