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

cork_south · 12-07-2023 4:52pm

https://www.boards.ie/discussion/comment/120842459#Comment_120842459

Yeah 2 lanes going to 4 coming out of the tunnel and no issues there.

Maybe this is expected with the Mahon slip joining but I'd have thought the queues back towards Douglas would have been a thing of the past with the junction free flow northbound.

markodaly · 12-07-2023 5:31pm

Not great if there are queues continuing along the N40 North at rush hour. Has the upgrade had any effect?

12-07-2023 5:36pm

https://www.boards.ie/discussion/comment/120791063#Comment_120791063

I try to observe posted signs and get all kinds of aggressive behaviour thrown at me

cork_south · 12-07-2023 5:42pm

https://www.boards.ie/discussion/comment/120842631#Comment_120842631

The tailbacks N25E are as long as they were before the upgrade but the traffic does move faster. After you get past the Mahon slip traffic flows relatively well.

Still a bit underwhelmed by it all, N25E in the evening time anyway. Right now schools are off and many commuters are away on holidays so it does not bode well.

mcburns07 · 12-07-2023 6:09pm

Surely it’s partially down to unfamiliarity with the new layout, speed vans, the fact it still resembles a massive building site despite the openings, unfinished surfaces. Way too early to judge.

cork_south · 12-07-2023 6:20pm

https://www.boards.ie/discussion/comment/120842829#Comment_120842829

Not sure about that, the problem area is well before the tunnel so building site is not a factor. Traffic flows fine around the area of the works.

The road layout in that direction has not changed recently, it's been like that for a few months. Right lane for M8N, left lane for town/N25E.

And I've yet to see a speed van on the N40E near the tunnel.

12-07-2023 6:28pm

They really need to start putting up signage for "MERGE LIKE A ZIP"

Irish drivers are predominantly clueless about merging.

The volumes are getting higher and they need to be making more effort to get people to make better use existing infrastructure, as well as trying to get more people over to public transport. The road network, even with these junctions, can't handle the volumes without some degree of clogging. The traffic volumes on some sections of the N40 seem far too high for a city this size.

Use of (and enforcement of) variable speed limits at peak time might also reduce the wave of brakes that you get in stop/start traffic, which I suspect is an issue around there. Keeping everything running smoothly from the tunnel to beyond the Douglas fly over would make a lot of sense.

Sorry to wander off the topic a little, but I think the infrastructural improvements are great, but they also need to be combined with better driver behaviour / education to maximise the benefits. You need an operation free flow type approach at peak times.

Glanmirelad · 12-07-2023 7:10pm

Maybe we should let cyclists use the tunnel lol

12-07-2023 11:05pm

It's bad enough as it is!!

It'll be interesting to see what happens as the interchange completes and people get used to the new layouts.

DylanQuestion · 13-07-2023 11:49am

Can anyone explain to me how this sign is to be read? Why does it say City Centre for both lanes, but then Cork and Limerick are two separate lanes? Also, why use City Centre on the N25 which is in the County but Cork on the N40 and M8, which are in the City

niloc1951 · 13-07-2023 11:54am

At rush hours the volume of traffic heading towards the interchange at 100km/h (or more!) and slowing to half that speed is a sure recipe for queues, it's simple physics.

I've seen 20km queues developing in the middle of nowhere on French motorways resulting from fast traffic catching up with slower traffic which occupies overtaking lanes as it overtakes even slower traffic. Once the fast traffic gets clear the queue magically dissolves, and not an intersection or lane closure in sight.

Variable speed limits to reduce the traffic speed well in advance of the pinch point does help to reduce the length of the queue.

Padraig Mor · 13-07-2023 12:39pm

https://www.boards.ie/discussion/comment/120845492#Comment_120845492

Very bizarre to 'split' the Cork and Limerick lanes several kilometers before the actual diverge.......especially as the Cork/Limerick lanes are actually the other way round at the diverge FFS!

DylanQuestion · 13-07-2023 12:57pm

Also both lanes for City Centre is wrong. Only the right hand lane is for the city centre (N8)

marno21 · 13-07-2023 1:13pm

It should just say:

Cork

Limerick (N20)

v N8 v

There should be no lane discrimination that far from the diverge. It just encourages poor lane discipline

KrisW1001 · 13-07-2023 1:15pm

https://www.boards.ie/discussion/comment/120845492#Comment_120845492

First, the Dunkettle interchange is in Cork City - the boundary was extended to cover it a few years ago.

The left panel is perfectly correct. The painted out bit will say "M8 Dublin". But the right panel is confusing. The M8 bit is a sticker which will be removed before opening, but the rest is a bit of a mess, with Cork signposted twice, and an instruction to drivers to form lanes when there's no reason to do so. It really should be something simple, like this:

An Lár
CITY CENTRE

Luimneach
LIMERICK

  N8 (N20)

🡇        🡇

... the use of "CITY CENTRE" is dictated by the signage manual, but that exposes the stupidity of this rule - which city centre? The only named place on the panel is Limerick, which isn't correct.

I really think we should adopt the "Centrum" bulls-eye icon (like ◉) used across Europe to show the way to town centres without having to hide their names on signage..

DylanQuestion · 13-07-2023 1:20pm

The way you have laid it out is exactly how I would do it too. My issue isn't them using City Centre, more them not using City Centre on the N40 and M8 where instead they just say Cork. For example, the signage in between the JLT and N40 J10 says CORK, when road users are already in Cork. The M50 uses City Centre, as well as the approach roads, so I don't understand why it wasn't the same here. And then other parts of the N40 use Cork (Centre). This is going to make even less sense once they erect the Welcome to Cork City signs and then there are signs further directing you to Cork.

Do you have a link to the signage manual?

KrisW1001 · 13-07-2023 1:25pm

The current signs manual is here: Traffic Signs Manual | trafficsigns.ie

DylanQuestion · 13-07-2023 2:02pm

I have emailed the relevant person at TII that it should read as follows. Given these signs are going to be there for years/decades, it's better for them to be right now instead of saying "ah well, people will figure it out"

marno21 · 13-07-2023 2:18pm

That sign on the right is also wrong. There should be no lane specific signage over 4km away from a particular junction with an intermediate junction also.

The signage before the upgrade commenced is actually the correct signage

https://goo.gl/maps/nZ4eG35HhZ6ovb6y7

Chris_5339762 · 13-07-2023 2:25pm

Agreed. You've done a nice mockup there, but its still wrong. Both lanes on the N25 should be the same in the final Dunkettle arrangement. You don't need to get into the right hand lane to go to Limerick.

Also they need to do the same type of thing approaching the tunnel. The signage is shocking on this scheme.

DylanQuestion · 13-07-2023 2:28pm

Apologies, you are both right. The signage overall is a mess, even though I contacted TII about it long before the scheme was fully started and they assured all would be fine..

cantalach · 14-07-2023 12:49pm

According to today's newsletter, the 30 kph on Link F is permanent. I think this really needs to be reconsidered. The curve isn't actually very severe at all, and as a few mins spent looking at the traffic cams makes clear, the insanely low limit is causing traffic to bunch up hugely going around that link. All it takes is somebody to break hard at the merge point with the M8S and you're into a multi-vehicle pileup situation on a single lane link.

marno21 · 14-07-2023 1:04pm

https://www.boards.ie/discussion/comment/120850309#Comment_120850309

Is it 30km/h to aid merging with the M8S flow? I haven’t driven it yet so I can’t judge myself

BagofWeed · 14-07-2023 1:27pm

https://www.boards.ie/discussion/comment/120850309#Comment_120850309

I had to brake at the merge point last night to wait for a gap as the M8 southbound had a bunched flow of traffic but there was no one behind me thankfully.

Shedite27 · 14-07-2023 1:30pm

https://www.boards.ie/discussion/comment/120850309#Comment_120850309

It's he same where the 270 degree turns are built on the M50, all 30kph

https://goo.gl/maps/8vCUw7pU9jBD9MNM7

AugustusMinimus · 14-07-2023 1:49pm

30kph seems extreme having driven it. 50kph limit would be more than enough.

KrisW1001 · 14-07-2023 1:51pm

https://www.boards.ie/discussion/comment/120850309#Comment_120850309

It's not an "insanely low" limit. This loop is only 100 metres diameter, and isn't much wider than the two 270-degree loops on the Red Cow interchange. Those are signed at 30 km/h, so this is the correct limit here. (This isn't an Irish quirk either: American cloverleaf interchanges have a 25 mph speed limit on the loops, even when the loops are much larger than this one)

The best way to avoid the risk of pile-up you speak about is for drivers to not be travelling fast as they approach the merge point.. like, for example, if they've just come out of a 30 km/h restriction?

cork_south · 14-07-2023 1:52pm

There was a speed van at the end of the loop this morning which could clearly be seen as you come around the loop so everyone was doing between 10 and 20 km/h

cantalach · 14-07-2023 2:45pm

https://www.boards.ie/discussion/comment/120850514#Comment_120850514

Yes, but the two tightest curves at the Red Cow are much more severe than Link F. Comparing side-by-side at the same scale:

cantalach · 14-07-2023 2:46pm

https://www.boards.ie/discussion/comment/120850645#Comment_120850645

It's actually quite hard to do 30 kph in a motor vehicle...feels unnaturally slow.

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

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