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

When the N40(N) -> N25(E) link opens, it will be a bit chaotic for the first few days as the lanes on the roundabout will essentially swap with the N40(N) -> M8(N) movement. Expect massive amounts of weaving as people get used to it.

Courtesy of Drone Hawk.

Not ideal but there are a few others like this on the national network. M1N/M50 to the airport turnoff and also the N7S/Redcow to the Luas P&R spring to mind. I'm sure there are a few others.

Here's the section between the tunnel and N40 East unrolled, and roughly to scale (dotted green line is where a barrier or even just a tiger-tail is likely to be used to separate traffic streams). It really is not as bad as people are making out:

The key point is that traffic on the N25East mainline is not involved in this junction at all, which greatly reduces weaving.

I picked through this a lot earlier in the post linked here: N8/N25/N40 - Dunkettle Interchange [under construction] - Page 61 — boards.ie - Now Ye're Talkin'

Good. But I hate to say that despite what they said they'd do, they made it worse for a few days again, as the crane came back.

So left hand lane for those heading east as someone else mentioned a few days ago .

One the interchange is completed could the lights at the Dunkettle roundabout end up causing those who are heading east on the Waterford road to get stuck in traffic I wonder. Good possibility.

Weekend opening of further slip roads possible?

The traffic generally doesn’t back up from the Dunkettle Roundabout back to the Dunkettle Interchange though.

Saying all this, it will be a great opportunity to up throughput as all 4 lanes can be used. People rarely use the right most lane at the moment on tunnel exit.

Not really. The total number of cars is not changing, the new slip will add more queueing space for Tunnel-Tivoli traffic, and right now, the Dunkettle Roundabout is already able to accommodate Tunnel-to-Tivoli traffic without causing backups. Once all the western exits lead to free-flow movements, the roundabout will be able to carry more traffic (right now, the backups at the Dunkettle Interchange are the major cause of delays on this roundabout). It may even be possible to remove the lights entirely but I suspect they will be left as-is.

Traffic from tunnel to Dunkettle Roundabout is being metered either the lights. When it moves to free flow, some of the traffic queuing through the tunnel will instead be queuing at the Dunkettle Roundabout. The only question is whether there is enough traffic for it to back up to the Dunkettle Interchange.

I get what you are saying but you'd expect that after spending close to 1/4 of a billion that the junction would be as close to free flowas possible, and not just hope that "overall delays to traffic turning west out of the tunnel should be lower than at present", seeing as the junction regularly backs up to Douglas and beyond at present.

Time will tell I suppose.

I think in the next 10/20 years there'll be plans to upgrade the Dunkettle Roundabout to a flyover. Coming from Tivoli, you'll have

....freeflow East.

....slip road to a mall roundabout with a left turn to Glanmire,

....opposite side of the new flyover will be an access road to the plans for Port of Cork

“Tailbacks to Douglas’ are not caused by the relatively small amount of traffic that goes through the Tunnel in order to head towards Tivoli. And no project, no matter how expensive, will remove the kind of freak traffic conditions that would see N40 Eastbound backed up that far today.

To explain why the new interchange actually helps traffic heading west here, remember that roundabouts are one-way roads, so every road off is potentially a source of blockage to every road on. If you free up traffic on the roads downstream of the roundabout exits, you free the roundabout, and increase its throughput. That, plus the increased queuing space between the tunnel and the Dunkettle roundabout will improve traffic flows west from the interchange... The lights on the roundabout are only a problem if they cause traffic for that motion to block the interchange. I have never seen that happen under the current arrangement, so why would it after the capacity there is increased?

We need to have some realism too: nobody’s going to spend another 50 million just so you don’t have to stop briefly at a set of traffic lights on your way into a places that are already full of traffic lights. There are national roads projects in and around Cork city that are far more deserving of that kind of investment (N71 for instance).

I think you may be underestimating the volume of traffic that heads to the city via the tunnel. Added to this the fact that this traffic is currently gated by the interchange lights and will flow directly to the RA once the interchange is complete.

Nobody knows what will happen but I think there is a good chance the lights at the RA will affect the flow of traffic northbound through the tunnel.