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

AugustusMinimus

I see the slip for N8 east to tunnel is making significant progress. However, the piece where the slip will curl to the left and cross over where the current roundabout to n25 east slip isn’t hasn’t started. That slip off the roundabout will first need to be closed to facilitate further construction. Anyone have any idea of timelines?

KrisW1001

https://www.boards.ie/discussion/comment/118993080#Comment_118993080

Only for Tivoli and the eastern tip of the City Centre, really. Most of the traffic landing withing Cork city already uses N40. There is a reason why it is this movement, rather than any of the others, that is routed like this, and that is that, of all the N25/N40/M8 interfaces that must cross another carriageway, this is the one carrying the smallest volume of traffic.

AugustusMinimus

https://www.boards.ie/discussion/comment/119004762#Comment_119004762

I cannot imagine that is true. M8 to N25 East and N25 East to M8 have little traffic. You barely see anyone queued to go from N25 to M8. Sometimes no cars on the slip at all when you have 20 cars to go through the tunnel.

Shedite27

https://www.boards.ie/discussion/comment/119004762#Comment_119004762

Do ya think coming down the M8, the sign at that junction for "Cork" will be through the tunnel or via Tivoli? Surely it's much longer to go around to the South Link, and they won't want all trafffic from M8/M20 coming in through South Link on top of existing traffic

AugustusMinimus

https://www.boards.ie/discussion/comment/119007049#Comment_119007049

City Centre will be signed using lower glanmire imo. Madness shoving more traffic onto the N40, Kinsale Roundabout and the South Link.

hans aus dtschl

Another detail also, is that a significant volume of traffic rat-runs to avoid Dunkettle completely at the moment.

The interchange is effectively not viable for the M8 to City East/North movement right now. So I wouldn't read into the low traffic volumes on that routing.

hans aus dtschl

https://www.boards.ie/discussion/comment/119007049#Comment_119007049

KRR too, is not free-flow for traffic entering the city from East. It wouldn't be ideal.

AugustusMinimus

https://youtu.be/o55C_bpTcVc

KrisW1001

Guys, I’m not proposing anything new or radical, I’m just telling you what is happening already, and the basis on which the decision was made. “Cork” as a traffic destination is not just Morrison’s Island: the enormous commercial and office development in Mahon, the light-industrial businesses all around the Togher junction, CUH, CIT, the Airport business parks - these all take and produce far more traffic than the city centre does these days.

I wish I could find the slide with the traffic graphs on it, but I think it was in a video presentation I saw... basically, the major movements at Dunkettle are South/East, North/East, and South/North. Very little traffic on the western arm. Yes, it looks crowded, but that's because the road is much narrower - N8 at Tivoli is a single carriageway, while N25 at the other side of Dunkettle is three lanes each way.

South from M8, turning right to enter Cork City by Tivoli is just not a heavily trafficked route compared to the other movements, and if/when the North Ring gets done, it'll be even less-used than now.

Anything that needed just an at-grade slip could be over-provisioned without much cost, but a dedicated M8/N8 link at the interchange itself would have required adding a third level to the interchange, and there’s no way that the low traffic numbers justified that (and there’s no way any of the other links carried on bridges could have been demoted).

hans aus dtschl

https://www.boards.ie/discussion/comment/119013097#Comment_119013097

I remember the traffic analysis that said that the M8 to Tivoli flow was the least volume. I believe it may have been on the Jacobs website. We possibly discussed it in this thread too.

I'm just adding my opinion of why that might have been the case, and also my opinion of the future plan. I've been moaning about the volume of cars rat-running off the M8 from Watergrasshill for a few years, I'm not going to stop now! In short, I think they made a mistake and that it won't be rectified without an N40 North section from Sarsfield's Court to Blarney.

AugustusMinimus

https://www.boards.ie/discussion/comment/119013223#Comment_119013223

Stunned if it has lower traffic than N25 west to M8 north.

hans aus dtschl

https://www.boards.ie/discussion/comment/119013349#Comment_119013349

The best reference point with real numbers that I could find is page 16 here: http://n8n25dunkettle.jacobs.com/docs/32102066_Dunkettle_EIS_VOL_2_Main_Body_MASTER.PDF

Synopsis:

Morning peak from M8 N

0.8% to North Esk

3.4% to N25 East

7% to the back of Little Island

10.2% to Tivoli

78.6% to the tunnel

It doesn't say that M8 to Tivoli is the lowest flow, but I do remember this being stated at some point, and it seems I'm not alone.

By comparison: N25 E has 44.6% heading to Tivoli and Tunnel has 19.3% heading to Tivoli. So what I'm saying (still!) is that the numbers are artificially low due to rat-running. I don't see how only 10% of M8 North are going to Tivoli, when the other arms of the interchange are registering much higher numbers to the same destination. I feel the answer is "because the people coming from the North are finding another way into the North and East of the city".

KrisW1001

The thing to watch is that those are percentages splits of the total traffic, so they represent a different number of vehicles every day on each approach. Fortunately, the next page of that report expresses the movements in terms of AADT, from which it’s possible to work back to the total approach traffic on each arm:

For example, from the East, the split is:

• South (tunnel): 49% (=13,000 AADT)
• West (straight ahead on existing bridge): 44%
• North (M8): 5.5%

If 49% is 13,000, then the total AADT is around 26,000 (remember that the study was done in 2010, and these figures are for only one direction of travel). 5.5% of that 26,000 total is around 1,500 per day.

Coming from the North, the split is

• South (tunnel): 78% (=7,500 AADT)
• West (city): 10.2%

Total AADT approaching from the North is around 10,000. 10.2% of that heads for the City, which is around 1,000 vehicles a day.

So, traffic from East to North is about 50% higher than from North to West, and that is why the East-North link was prioritised over the West-North one.

Regarding “rat-running”, I think the route of the M8 itself is the reason why so many people to the North-East of the city do not take M8 if their destination is within in Cork City.

hans aus dtschl

Yep I had a hunch it was AADT rather than %. But I don't have evidence.

Absolutely correct on the rat-running. These people actively avoid the M8 (most specifically Dunkettle). I know plenty who do this.

Others head East at Watergrasshill towards Leamlara, in order to more reliably access Carrigtwohill and Little Island. The M8 is dysfunctional as it nears Cork.

DylanQuestion

I feel like Cork is the only city in Ireland that has a small town mentality when it comes to road signage. Dublin roads refer to "city centre" on the N2 north of the M50, on the N3 north of Blanchardstown, on the N4 by Liffey Valley, etc. It's the same in the outer parts of Waterford (https://goo.gl/maps/bG4EEjWv2f5wSGbV6), Limerick (https://goo.gl/maps/PDBbbCzHvrb5n75b7) and Galway (https://goo.gl/maps/dEcLZRLQeDAkos5b9)

The city centre is just that, the city centre. It is where the N8 leads to. Not the "city" (as is shown on the VMS screens and road markings on the N27) or "Cork", like many road signs show, especially on the N28, N71 and at Dunkettle. The Dunkettle is the official entrance to Cork from the N25 and M8. The N40 is as much a route to the rest of Cork as the N8 is.

The road signs at Dunkettle for the N8 should read:

City Centre N8

Cork (North) (R635)

Glanmire (R639)

For the N40, the signs should read:

Cork (South) N40

Westbound

Cork Airport (N27)

Ringaskiddy [Port Symbol] (N28)

This is already done in a few places in Cork, like here (https://goo.gl/maps/U91Tixk9d12mLVTW7, incorrectly saying Cork East instead of Centre or North) and here (https://goo.gl/maps/E7pLvn9mfbrrMoNZ8). You can see a better example using City Centre and (South) in Waterford here (https://goo.gl/maps/f6yx2re1sRBxe5s59). I really don't get why road signs in Cork have to be so.. meh when it comes to the city centre. I noticed the road signage on the N27 at Bull McCabes had City Centre N27 changed to Cork N27 in 2010, and all mentions of City Centre on the N28 signage (and N40 signage in Rochestown) was replaced by Cork

AugustusMinimus

Great update from Drone Hawk.

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

DylanQuestion

I drove here for the first time in a while yesterday. I was really surprised by how long the 60km/h limit lasted on the N25 when going eastbound. It went on way long after the roadworks had finished, all the way to Little Island. It then only changes to 80 too until it randomly changes to 120km/h a kilometer or so down the road. I was thinking maybe both sides need to be the same speed, and westbound may need to be slower as they are approaching the roadworks. However, the two directions are fully segregated. Is there a purpose to this?

iColdFusion

Snip from the video above, it's mad where they put the sign indicating the new M8 slip, heard a few people have accidentally tried to drive up the cycle lane already, the sign literally points them to do that!

DylanQuestion

https://www.boards.ie/discussion/comment/119011113#Comment_119011113

Does anyone know what is up with N40 being blocked out on the sign at 2:27? I'm thinking maybe so people don't think the M8 slip road is also for the N40. However, that sign wasn't there in October 2021 looking at Google Street View (well, it is, but M8 and N40 are flipped and there's no coverings on anything)

confidentjosh

https://www.boards.ie/discussion/comment/119034592#Comment_119034592

Id say it's to indicate the new slip road that will feed in to the new Glounthaune roundabout at the other side of the Gaelscoil. This stretch of road will run parallel to the railway line & under the new M8 bridge but hasn't been completed yet. Essentially instead of veering left to take the M8 north you will also be able to drive straight under the new M8 over bridge and on towards Glounthaune on the old main road.

Chris_5339762

https://www.boards.ie/discussion/comment/119034013#Comment_119034013

Its agonising. But I think the reason it's there is that you can't go down directly from 120kmh to 60kmh. You have to have an intermediate bit of 80kmh.

This won't effect M8(S) because thats 100kmh only - so can go straight down to 60kmh.

The fun starts when you actually drive at 60kmh and nearly get killed, each and every morning.

hans aus dtschl

https://www.boards.ie/discussion/comment/119035358#Comment_119035358

If you've driven the N25 at 60kmh you're one of very very few.

It is exactly as you say: terrifying. I'm just avoiding it at the moment as best I can.

marno21

https://www.boards.ie/discussion/comment/119036147#Comment_119036147

Has there been any enforcement along the stretch?

Chris_5339762

I've once seen a garda car at the tunnel, everyone was weighing anchor.

Its the same as at the M7 upgrade works near Naas, I hated doing that at 60kmh but that was the speed limit and if there is one place the guards are going to do speed checks, its in the roadworks, not on the dangerous bend with limited overtaking opportunities.

hans aus dtschl

I have not seen any enforcement, but as I say I have been avoiding the stretch as much as possible. Maybe I've done it 10-20 times Westbound.

I've done Eastbound a lot more often than that and can't imagine where they even would have enforcement placed there.

mcburns07

Drive it every day, have never seen a speed van or Garda car. Majority of people do 90-100 in the 60 zone.

AugustusMinimus

https://www.youtube.com/watch?v=S42_vmd-Zbc

Great video especially for those unfamiliar with the area.

Video also shows the ongoing road improvement scheme in Glanmire village and around Ballinglanna development.

Jippo

I assume the slip from the primary school at Dunkettle that goes directly into the tunnel (almost) is not in the final plans?

AugustusMinimus

https://www.boards.ie/discussion/comment/119045871#Comment_119045871

That will be closed eventually. Access will be replaced by using the new dumbbell junction.

hans aus dtschl

https://www.boards.ie/discussion/comment/119045828#Comment_119045828

What's being described as "road widening works" on the L2998 is likely the greenway scheme. Note also the use of trucking curb under the M8 bridge from L2998. Also note the new pedestrian and cycle crossing which couldn't possibly be done atall atall atall in the original revision. Some good details going in recently: good job all!