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

AugustusMinimus

I don’t understand why both bores are almost constantly closed for maintenance works. Why not use a contraflow setup more often which would stop creating traffic chaos after 9 each evening.

If water ingress truly is an issue, what can be done about it? Would they need to dry dock specific areas of the tunnel and do work on the outside of the concrete sections?

hans aus dtschl

As I understand it, the sections are covered in silt/earth/etc rather than being purely exposed concrete. Also, the weight of the water would be enormous

niloc1951

Probably a leaking joint as a result of poor workmanship during construction, now impossible to do a permanent repair on the outside and needs regular patching up on the inside.

Patching a leak from the inside to keep water on the outside out is never a permanent repair, that's why a ship with a hole in the hull needs to be dry docked.

cantalach

The “dúirt bean liom go ndúirt bean léi” water ingress rumours could easily be settled with an FOI request…

cantalach

I saw there was a 7-8 km tailback on the N40E yesterday due to an accident at the northbound tunnel exit. Presumably this was caused by somebody jumping lanes left-to-right for the M8, or right-to-left for Tivoli. Unfortunately, a huge percentage of the population somehow misses the multiple enormous overhead signs before entering the tunnel northbound.

I think they need to consider putting a physical divide between the two lanes that goes right through the tunnel and continues on the other side until past the M8 and Tivoli exits. The inconvenience this will cause to people who can’t follow signs is easily trumped by the lives that will eventually be saved (potentially their own) if this goes on.

KrisW1001

https://www.boards.ie/discussion/comment/122714563#Comment_122714563

A barrier can't be put in place, as it would not give traffic joining at Mahon Point enough time to safely reach the right hand lane. The result would be an increase in collisions where the Mahon Point onramp meets N40 as cars try to cut across two lanes.

TheSunIsShining

https://www.boards.ie/discussion/comment/122596350#Comment_122596350

https://jacklynchtunnel.ie/tunnel-closures/

Be easier at this stage to just announce it will close every night on a permanent basis

cantalach

https://www.boards.ie/discussion/comment/122714644#Comment_122714644

It is 1.2 km from the end of the Mahon on-ramp’s merge lane to the tunnel entrance. If that’s not enough distance for people to move one lane to the right then we need to invest in driver education!

KrisW1001

https://www.boards.ie/discussion/comment/122714692#Comment_122714692

But you're proposing a barrier that would be in place before the tunnel entrance, which will considerably reduce that available distance.

Mainline traffic travels at 80 km/h here (but many drivers exceed this speed), 80 km/h is is 22 metres per second so there's 54 seconds from the end of the merge to the tunnel mouth. In situations where traffic is heavy but still flowing freely, merging to the right lane is already difficult…shorten that available time, and you will increase the risk of collisions.

cantalach

That’s an insane schedule! Works out at 112 hours in Oct and 84 hours in Nov!

cantalach

https://www.boards.ie/discussion/comment/122714721#Comment_122714721

I didn’t actually say before the tunnel entrance. I said “right through the tunnel” but, yeah, I guess it would have to start st least some number of metres before the entrance. But even if that was 50 metres that still leaves 1.15 km to change one lane. I think people should be able to manage that, and you don’t which is fine.

The current situation is untenable though. Much and all as I’m queasy about cameras being everywhere, I think safety would justify use of average speed cameras right through the tunnel with a 60 kph limit on the northbound side. Otherwise it’s only a question of time before there is loss of life or life-changing injuries.

Edit: The vagueness of the M8 arrow on the overhead signs is another factor but we’ve already discussed that to death in this forum.

TheSunIsShining

https://www.boards.ie/discussion/comment/122714723#Comment_122714723

It certainly appears so. Like I said. Be easier to just either permanently close it at night or else tell people to assume it's closed but publish the nights it's going to be open!

chooseusername

https://www.boards.ie/discussion/comment/122714754#Comment_122714754

Why put barriers in the tunnel, there's no lane changing in the tunnel anyway? Barriers after the tunnel until after the M8 turn-off and channel traffic in the left lane over to the Dunkettle roundabout back on to the M8 that way with proper signage.

cantalach

https://www.boards.ie/discussion/comment/122715827#Comment_122715827

Lane changing might not be permitted in the tunnel but people do it all the time. Also, if the barrier were to start at the exit from the tunnel, this would encourage more braking and lane changing in the tunnel as people make a last second course correction.

niloc1951

https://www.boards.ie/discussion/comment/122714754#Comment_122714754

Reducing the speed limit to 60 kph on the northbound side would only exacerbate the eastbound queueing at busy times.

cantalach

https://www.boards.ie/discussion/comment/122726904#Comment_122726904

How so, particularly if combined with variable speed limits on the N40?

niloc1951

https://www.boards.ie/discussion/comment/122727736#Comment_122727736

It's an accepted fact that practices such as tailgating, frequent lane changes, and impeding the free flow of traffic such as slowing vehicles up ahead, can reduce a road's capacity and cause or exacerbate jams.

Here's the science https://eng.libretexts.org/Bookshelves/Civil_Engineering/Fundamentals_of_Transportation/05%3A_Traffic/5.03%3A_Queueing_and_Traffic_Flow

mydiscworld

Sorry posted this is wrong thread yesterday…

https://www.rte.ie/news/business/2024/1016/1475678-lidl-plans-new-200m-regional-distribution-centre-in-cork/

The company is to seek planning permission for the new facility at Wallingstown in Little Island.

This certainly won't help the East Cork traffic if granted

niloc1951

Having a few minutes to spare on a bank holiday Monday I spent 5 minutes watching the N40 North of Tunnel video relay in the early afternoon as the many visitors to our city began to return home..

In the five minutes, I watched four near misses as drivers made the last-minute dive from lane 1 to the M8 slip. While we locals have probably learned to ignore the misdirections on the overhead signs, they obviously catch out the visitors.

chalkitdown1

https://www.boards.ie/discussion/comment/122772422#Comment_122772422

It's absolutely ridiculous (and clearly incredibly dangerous) that the big blue Dublin sign spreads over both lanes. Didn't someone in this thread make an official complaint about it and was told there was nothing wrong? Or am I imagining that?

Chris_5339762

I remember someone messaged the contractor who said "we're happy with it, FO". But I don't think anyone has emailed TII about it. Maybe thats the next step.

niloc1951

Given the catastrophic consequences, like a 5km tailback, that a crash at the north exit from the tunnel can cause, isn't it important that all direction signs are clear and unambiguous, especially to strangers to the area

DylanQuestion

https://www.boards.ie/discussion/comment/122779304#Comment_122779304

Yup, that was me. I sent it to the contractor but it was TII who responded to me. They were referring to the City Centre/Cork/Limerick mess on the N25, but it applies to the whole scheme:

"Thankfully the signage strategy appears to be working well, with many thousands of motorists successfully navigating the Interchange on a daily basis. However, the operation of the Interchange is being kept under regular review and any problems identified with the signage will be rectified as necessary."

Their reasoning for the N25 mess was that those heading to the City Centre can use any lane, but those heading to Limerick should be in the right hand lane. Those going to parts of Cork not in the City Centre (like Douglas, Wilton, etc) should be in the right hand lane so that they can merge towards the N40. The reason I raised this at all was that I believe it should be Cork on top, City Centre on the right and Limerick on the left. But they have it as City Centre on the top, Limerick on the left and Cork on the right. Which is completely at odds with their reasoning (why would you merge towards the N40 for the city centre), as well as being at odds with the N8 (Limerick traffic on the left, City Centre traffic on the right)

hans aus dtschl

I had some silly answers when I questioned the design of the cycle routing through the interchange too. Along the lines of "the reason this design is safe is because it can't be safe". TII backed them to the hilt unfortunately.

EnzoScifo

It has got to the point that if I am in the right hand lane going through the tunnel, I am scanning the left hand lane for any D reg or foreign cars to give them a wide berth!

chooseusername

Took a minuute or so to find this one.

They did make it, luckily no traffic about.

M 8 Swerve.jpg

niloc1951

Given the catastrophic consequences for commuters of even the slightest crash in the area of the JLT or DI the signage should be absolutely unambiguous and totally idiot/stranger proof.

chooseusername

Two more in quick succession;

M8 Swerve 2.jpg

M 8 swerve 3.jpg

DylanQuestion

https://www.boards.ie/discussion/comment/122789837#Comment_122789837

I completely agree. They’re trying to show too many things at once. It also now longer lines up with the N40 signage. The N40 used to have Cork (West) at N22, Cork (Centre) at N27 and Cork (East) at JLT. Now JLT just says Cork. The Cork (West) signs were recently upgraded and (West) wasn’t removed. As a whole network, all of the signs make little to no sense.

• N40 should just use City Centre, West/Eastbound and the neighbourhoods
• JLT northbound just needs to show signs for Cork (North), City Centre and Limerick left, Little Island and Waterford across both and Dublin on the right
• N25 westbound should show just Cork until Little Island J2, where it should then split to Westbound and Cork (South) on the left, Limerick and Cork (North) in the middle and City Centre across middle and right
• M8 southbound from Glanmire J18 should show City Centre, Cork (North), Waterford and Little Island left, and Westbound and Cork (South) right

They made the whole thing so much more complicated than it needs to be

bigtimecharlie

https://www.boards.ie/discussion/comment/122772422#Comment_122772422

How do you do replay of the feeds?