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

markodaly

Sorry if this has been posted before but, does anyone know when the ETA is for this being finished? I think its about 2024 from memory.

Mushy

https://www.boards.ie/discussion/comment/119280650#Comment_119280650

Early 2024, think February was mentioned in the emails

AugustusMinimus

Huge work done on the new dumbbell. You could see a partial opening in 3 or 4 months, especially to open the link between Glounthaune and Little Island. This will facilitate closing the slip into Little Islsnd off the Dunkettle Interchange.

KrisW1001

Early 2024 is when all of the new movements will be open to traffic, but it's not a Big Bang opening: movements will open as they are completed, so that the old interchange will gradually turn into the new one.

AugustusMinimus

Fantastic footage from Drone Hawk as usual.

https://youtu.be/i0pdwa9M8yI

hans aus dtschl

What are the blue pipes on the bridge footpaths? Is it just being used as a staging space?

cargo

https://www.boards.ie/discussion/comment/119292574#Comment_119292574

Underground heating... the people of Cark are too important (in their own eyes) to walk on cold footpaths 🤣🤣

I'd say it's just fibre ducting been staged on the bridge for now. Looks to be too many ducts for but maybe they are going to lay loads to future proof but there's only one power duct either side of the bridge so light on that.

hans aus dtschl

Your thoughts echo my own! I was wondering if there were laying loads of extra ducts to future proof it. Little Island is a big industrial area after all, and I wonder if there are some known future demands.

And I also was thinking of some lovely "heated" footpaths and cycle lanes abroad in cold countries, which are automatically ice-free throughout winter. :D

AugustusMinimus

https://www.boards.ie/discussion/comment/119298409#Comment_119298409

I don’t think I’ve ever seen a signalised dumbbell before.

Cookiemunster

https://www.boards.ie/discussion/comment/119299912#Comment_119299912

It's a national route controlled by TII. Cork CC will do nothing without their permission, so there won't be any traffic lights appearing.

KrisW1001

The Dunkettle Roundabout is an at-grade junction (just as the current Dunkettle Interchange is); a dumbell interchange is not. At-grade junctions regularly have traffic lights on them, especially where traffic volumes are high.

Jayuu

Quick question on this. It may have been answered before but I can't find anything in my scrolling back. Will this be opened in a piecemeal way as new alignments come onstream or is there a big bang opening planned. If it is a big bang approach are there timelines around that?

AugustusMinimus

https://www.boards.ie/discussion/comment/119313288#Comment_119313288

Has to be done piecemeal as the build is on top of an already existing junction. The current roundabout will likely even cease to exist within the next year of construction.

In fact, new sections have already opened being the M8 bridge over the railway line and the N8 east to M8 north slip road.

AugustusMinimus

https://www.youtube.com/watch?app=desktop&v=2fir0aSrqeY

Great as usual from Drone Hawk. Comparison of July 2021 to July 2022.

Huge amount of work done especially on the South East of the junction which is largely going unseen.

Mushy

On the most recent video (in email and time-lapse one posted above), when it flies over the N8S to N25E, there's a road thats merging to it just south of the tracks. Is that the N40N to N25E link?

Chris_5339762

Give us a timestamp and I'll have a look!

Mushy

It's at 0.54 into the most recent video posted above. Looked at the drawings and it looks like it is, think I'd just forgotten how far north that link is going to go.

I imagine it'll be a long way off until that link will be fully completed, although does it need to be done so the n25e to n40s link can be completed (as in, removes that slip road out of use)? Would make sense for it to happen, to my uneducated eye.

Hibernicis

It's the N40 North to

1 N25 East

2 Glounthaune, via the dumbbell

3 Little Island, via the dumbbell

As shown in the bottom two maps here: https://www.dunkettle.ie/media/1339/traffic-movements_from-n40.jpg

Mushy

https://www.boards.ie/discussion/comment/119383098#Comment_119383098

Those drawings are great. I absolutely cannot wait for that dumbell to be done and traffic can use it to head east, will free up the current junction so much

serfboard

https://www.boards.ie/discussion/comment/119383098#Comment_119383098

Would anyone else share my concern that the split between going to Glounthaune and going onto the N25 looks fairly tight, with very little time to make the right choice? Last-second lane changes may lead to collisions.

Mother Trucker

https://www.boards.ie/discussion/comment/119384533#Comment_119384533

Looks like a potential problem to me, all right.

A bit shortsighted, perhaps .

Let's hope we're proved wrong.

Mushy

https://www.boards.ie/discussion/comment/119384533#Comment_119384533

I was actually going to say would people on the link be directed to go to the current flyover as they do currently. Not much can be done to prevent it happening, but had the same thoughts.

Chris_5339762

Its a concern alright, and a concern for traffic too.

It'll likely have a 60kmh limit, but whether people will obey that, who knows. Doing this loop and merge at 60kmh wouldn't be too bad but if people gun it to 120kmh, it'll be bad.

Mother Trucker

They could stick a speed camera up there and that could mitigate the problem somewhat.

hans aus dtschl

https://www.boards.ie/discussion/comment/119384533#Comment_119384533

No sh1t.

I've been banging on about it for literally years in this thread. I think it's a mistake and I've thought it was a mistake from the start.

I believe that nobody is going to obey the speed limit there and it's going to be a regular crash location. Then the Dublin-Cork movement will back up too, and it'll affect the whole interchange. Dublin-origin traffic will rat-run through Glanmire.

KrisW1001

No, it’s fine. It's a lot safer than the old arrangement that had M8 traffic racing the lights on the roundabout. Complex free-flows look difficult to navigate on a map, but in reality, you just follow the signs and markings, and you're through with very little effort. Here there's only one weaving section, but it's only between two adjacent lanes, and the junction is likely to be under a 60 km/h limit (maybe 80), which will make it very easy to navigate. People don’t break the speed limit on other complex free-flows, so I don’t think there’s something uniquely stupid and reckless about Cork drivers that would make them try to take the whole thing at 100 km/h. When quiet, most traffic will probably traverse the junction at around 70 km/h, so someone trying to barge through will not get far among other slower cars. At peak periods, it’ll be more like 40 km/h, which makes negotiating lane changes easier.

The key thing to note is that traffic on the N25 mainline here cannot access the new Little Island West exit. Once you realise this, the whole thing makes sense.

I posted the remaining a lot earlier in this thread, but this is a summary:

Here's the movements on N25 West. Blue is from South Ring, Orange from M8, Green is the N8/N25 mainline from the city. (Red lines are the various movements out of Little Island West, and can be ignored here).

Blue (from South Ring) is 2 lanes, Orange (from M8) is one lane.

From Point A (M8 joins) to Point B (new Little-Island leaves) is three lanes.

At point C (end of tiger-tail for traffic joining mainline), there are five lanes, merging down to the three just beyond the new dumbbell junction.

The planning documents contain a 3D rendering of the road including the stretch from Point A to Point B, where you can see this.

The movements along here are not challenging, and you can see from the mockup that everyone has a very clear view of neighbouring lanes in the section where traffic has to sort.

M8 South to Little Island West: Stay in lane, leave at first exit to new dumbbell.

N40 South Ring to Little Island West: Move to left lane after tunnel, move left again after M8 traffic joins (Point A), leave at first exit onto to new dumbbell.

M8 South to Glounthaune/Little Island East: move right one lane at Point A, merge with N25 mainline at Point B, leave at next exit.

M40 South Ring to Glounthaune/Little Island East: Stay in lane at point A, merge with N25 mainline at point B, leave at the next exit.

N25 (from City) to Little-Island West: There is no access at all to the new junction for you here, but that’s okay because you are not even on this road; you already exited further West, and will approach the new Little Island West from the North.

For (a lot!) more detail, the design drawings are here:(http://n8n25dunkettle.jacobs.com/docs/32102066%20Dunkettle%20EIS%20VOL%203%20Figures%20-%20Fig%201.1.1%20to%20Fig%202.4.1.PDF)

hans aus dtschl

Kris, everything you wrote is correct and we've been through it previously.

But still we have effectively an accident blackspot on the N25 between Little Island and Cobh Cross. People are terrible at driving.

Firstly, I believe people will try to get from Tunnel to Little Island West

Secondly I don't see them getting the "M8 South to Midleton" and "Tunnel to Midleton" merges right in such a short space.

We'll see though. We've discussed this at length in this very thread, and as I said before I'll be happy to be wrong.

marno21

It would remind you to an extent of the northbound Bloomfield interchange, which seems to cope reasonably well enough despite the high speed approaches from the south and the volume of traffic involved.

The main worry here would be speeding but that can be addressed if needs be

AugustusMinimus

https://www.boards.ie/discussion/comment/119388170#Comment_119388170

The section on Bloomfield you talk about just requires some courtesy between drivers during times of high traffic. It works well.

KrisW1001

It's also similar to how the cars from the N40 West/Togher exit on Kinsale Road Roundabout intermingle with N27 traffic for Togher and the N40 mainline (here: Cork, County Cork - Google Maps). I use this regularly, and I don’t remember ever seeing an incident. In this situation, the joining flows are speed-limited by the traffic lights further back, but despite that, cars are normally travelling at up to 80 km/h by the time any lane-changing happens.

The proposed merge at Dunkettle is longer than this, and has much better sightlines.

Where I can see a greater opportunity for accidents is at the diverge from N25 Westbound, where drivers have to decide between Little Island West, N40 South and N8 North, but I believe the traffic will be well streamed by signage and markings before those decision points, and unlike the two Douglas exits on N40 that cause so muchtrouble, each choice will be distinctively signposted.

(Briefly off-topic, but I believe that if those two exits were signposted "DOUGLAS | GRANGE" and "BALLINLOUGH | ROCHESTOWN", rather than "DOUGLAS(west)" and "DOUGLAS(east)" there would be fewer accidents - having the same destination shown for the two exists, with only tiny “east” and “west” text to distinguish them makes it a lot easier for drivers to accidentally choose the Western exit, then have to dangerously abort that exit and jump back into the mainline)