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

Nobody is saying we shouldn't do Dunkettle. Some are saying that we should do far more!

In terms of crystal balls, we are almost all agreed that this project will not solve N40 problems. It doesn't need a genius to see. Most of us are also agreed that further N40 expansion will not solve N40 problems. We now likely need progress on N40 North and heavy investment in sustainable transport solutions.

It's the Glashaboy bridge that's getting treated I think? So there will be no Westbound connection over Glashaboy river whatsoever. I'm not fully sure what your proposed alternative routing is, but I can't see anything available other than a routing via Glanmire Bridge (L2998) which just wouldn't cope with the volumes of traffic.

I don’t think I am. Seeing very significant tailbacks each morning from Bloomfield is just a realistic expectation.

We were told continually in the Bandon/Sarsfield flyover thread that there would be not additional tailbacks at the Douglas flyover. This was simply incorrect.

There may be an increase in traffic levels due to people no longer avoiding the junction. This isn’t the crux of the argument though.

There are big queues back up both the M8 and N25. These traffic queues will simply move on to the next choke point which will be Bloomfield / Douglas Flyover. I think it’s a possibility that queues could reach back to the tunnel in the mornings, at least at the start. People will modify their behaviour to avoid traffic by leaving earlier / later or by taking alternative routes (less likely as there are very few if any alternative routes.

My mistake, I thought the closure was for the finishing touches on the bridges over the Dunkettle roundabout, which were featured in the close-up photos of ongoing waterproofing.

The lights at the current Dunkettle create an uneven distribution of traffic downstream of the interchange: the lights collect the traffic into closely-spaced platoons, with clear road between each platoon. This kind of distribution can cause congestion at lower levels than if the same number of cars were more equally spaced on the road. (A big cause of congestion delay is lane changing into small gaps; tightly packed groups of cars increase the chance of this happening)

Or, for the tl;dr - I think that traffic flow through Douglas flyover will actually improve after Dunkettle is complete, even if there’s more of it.

The theory behind what you’re saying makes sense.

My worry is that traffic coming through the tunnel will be as compact as it is now, except you will no longer have the gaps which are present at the moment due to light sequences.

We’ll have a constant flow in lane 1 from the N25 and lane 2 from M8 and city.

The key though is that the capacity / through put will increase with this junction improvement. Agree that the traffic won’t be as metered in the past. However, the increase in spacing out of cars will be marginal in my mind if at all. The gain in capacity will be due to cars filling the voids that were created by traffic light sequences.

Completely agree on your second point though. There is a limit on what can be done with the N40. It’s getting to the point of diminishing returns for additional spend. Other options will be focused on in future, mainly focusing on other modes of transport.

The fix is not to widen N40, but instead to provide a proper east-west distributor road for the South-side of Cork (including public transport and active travel provisions), so that people won’t be drawn onto N40 when all they want is to get from one side of Douglas/Grange to the other.

Good point, but ultimately neither M28 nor traffic taken from Dunkettle will use a distributor road. They'll stay on the "fast" road, not the distributor which will be functional but likely 50 or 60kmh with traffic lights. They certainly won't come off the M28.

We should probably all head to the N40 thread with this instead of cluttering up the Dunkettle thread.

No mention of Link F in todays update.

Embankment work has restarted on the N25 to M8 north slip I see.

I think they’ll also line the inside of the loop with barrier. Outside is now largely complete.

Yes actually, they've finished the bridge tie-in and tarred all that. Steamrollers going along there as of now sorting the tar. Final lining and all that to do only? This weekend maybe, but I'd certainly hope before end-April. I guess just sorting out traffic lights now.

One set only where the N8 (City) down ramp onto the Roundabout was.

I think it will also result in part of the roundabout closing between the current M8 exit and M8 entrance. It won’t be required anymore.

I reckon you're pretty much spot on with all of that. The only thing I think is they'll keep lights on the "roundabout" for as long as possible to regulate flow for now. Certainly I think they'll keep the lights on the eastern side for some time yet... so M8S to tunnel, N25E to tunnel (new loop) + N25W to tunnel.

I looked up those concrete retaining walls before, there's some info here: https://reinforcedearth.com/products/retaining-walls/mechanically-stabilized-earth-mse-retaining-walls/

They seem to have reinforcement strips that attach to them back of the piece of concrete and stretch out into the back fill behind and hold the pieces in place

In today's newsletter

• The N25 westbound will be closed from 7:30pm on Friday 21st April 2023 to 9:00pm on Saturday 22nd April 2023 to facilitate the works with the main diversion route via the Jack Lynch Tunnel, N40 and the Cork City South Ring Road for the N25 and the M8 traffic (see layout plan below).
• Traffic approaching from the N40 and the N28 will be diverted via the Kinsale Road Roundabout and the Cork City South Ring Road.

Would somebody tell TII that the Cork City South Ring Road which they are obviously referring to in the above diversion route is, in fact, The South Link Road, AKA the N27 and the N40 is the South(ern) Ring Road. They seem to have their links and rings mixed up

Nope. Traffic cannot go westwards from the Dunkettle Interchange to the Dunkettle Roundabout. That includes all traffic coming from M8 north, N25 from Midleton and traffic from the tunnel.

The diversion is ludicrous. Anyone in the know will go through Glanmire.

They will indeed.

But if I am coming from Rochestown and heading for Midleton.

So that's N40 - Tunnel - N25 East, I will not at all be impacted by this?

They are not saying that. The quote is "Traffic approaching from the N40 and N28 will be diverted via the South Link". That makes no sense. Traffic approaching the tunnel heading WEST will be diverted. Traffic heading EAST will not. But that's not what they've written.

The only impacted structures are N25 Westbound, and Tunnel Interchange Westbound. They've just written a somewhat garbled description.

The embankment just north of the tunnel exit is making great progress. Much faster than expected.

Agreed. Almost everybody who's reading the email in the detail that we are, probably understands!

The same counsellor liked a comment complaining about the Ibis slip being permanently closed. Has this guy even looked at the plans? I hope he doesn’t represent the average level of local government in this country.