N8/N25/N40 - Dunkettle Interchange [under construction]

I had a look back through my dashcam footage as I went around the roundabout.

It looks like the signs say: "For updates register with roadconstruction@ccc-site.com".

The whois for the domain gives Cork County Council as the registrant (set up for the Ballincollig Bypass, it seems) so I'll shoot an email off and see what happens.

mire wrote: »

Am i right in my interpretation off the scheme drawings that northbound tunnel traffic heading to Dublin will be reduced to one lane for the course of the intersection? Is this 1. correct? 2. A problem, in reducing this flow to one lane?

http://n8n25dunkettle.jacobs.com/docs/32102066%20Dunkettle%20EIS%20VOL%203%20Figures%20-%20Fig%201.1.1%20to%20Fig%202.4.1.PDF

I doubt more than 50% of traffic goes SRR to M8. Can’t see it being an issue even in peak traffic.

grogi wrote: »

AugustusMinimus wrote: »

I doubt more than 50% of traffic goes SRR to M8. Can’t see it being an issue even in peak traffic.

Majority of traffic from SRR turns East toward Midleton. The proportions might change in far future when NRR is opened though and south side goes through the tunnel, M8 towards NRR and finally N20.

Still though, I doubt only having one lane for SRR to M8 will give much of an issue especially given that SRR traffic will be split into 3 different streams going through Dunkettle

SRR to City
SRR to M8
SRR to N25

You would want maybe 60% or more of SRR traffic using just one movement before you would see anything noticeable. The reduction in speed to 50 or 60kph at the junction will also increase capacity versus what the SRR handles at 100kph

mire wrote: »

AugustusMinimus wrote: »

Still though, I doubt only having one lane for SRR to M8 will give much of an issue especially given that SRR traffic will be split into 3 different streams going through Dunkettle

SRR to City
SRR to M8
SRR to N25

You would want maybe 60% or more of SRR traffic using just one movement before you would see anything noticeable. The reduction in speed to 50 or 60kph at the junction will also increase capacity versus what the SRR handles at 100kph

thanks for the replies; not sure though. the cork metropolitan area is planning to grow very significantly to 2050, how about future proofing the infrastructure? this SRR-M8 movement is likely to experience growth, substantial growth.

I think the fact that the tunnel is only 2 lanes in each direction was also taken into consideration when doing this junction.

I doubt it will ever be widened to 3 lanes as the cost would be enormous. This will be the limiting factor on capacity rather than the junction.

Alternative options will be put in place. Bridge by Pairc Ui Chaoimh. North Ring Road. Possible further down stream crossing (Rushbrooke to Passage West)

Carawaystick wrote: »

I presume a safe cycling route to get through this junction is the first thing being done here...

There is mention of cycle infrastructure in the EIS document. Particularly on page 12 or so, it's listed as the 5th priority of the upgrade (after improving capacity, minimising impact, segregating local and strategic traffic, and mimimising weaving).
To this end they mention
"
It is an objective of the scheme to ensure that any solution also includes the provision of pedestrian and cyclist connectivity through the proposed scheme. This facility should coincide with other planned pedestrian and cyclist facilities in the area and also separate these movements from the main traffic movements through the interchange where possible. This objective therefore promotes more sustainable transport modes and will also assist in accessibility between the various areas currently severed by the existing interchange"

You'll find the drawing of this aspect of the design on figure 2.1.1.

Their plans are for pedestrians and cyclists to dash across the Cork-Dublin slip road. When I pointed this out to them they advised me that since traffic would be going at 50kmh it would not be a problem.

Speaking as a cyclist who currently uses the interchange, I believe that this design will very effectively move all cycle traffic away from the Dunkettle area and end cycling as a mode of transport through this junction once and for all.

marno21 wrote: »

In most areas these roads would be motorway, they are in Dublin (you won't find cyclists or pedestrians on the M1, M4, M7, M11 or M50). They realistically should be and in the case of the N22 and N25 will likely become motorways when they are extended to Macroom and Youghal respectively. They are no place for cyclists, cyclists should not be crossing 120km/h on/off ramps at grade. Cyclist facilities should be provided on either the roads they replaced or totally segregated.

If you live in Swords you don't cycle to Dublin via the M1. The same should apply in Cork with the N25.

How do you cycle between Glounthouan or Little Island to Cork? It's not like there's the old road to use like from Swords to Dublin.

The NRA have failed in their mandate to provide the safe cycling infrastructure up to now, and should provide it as the first stage of construction works.

Ideally you’d have a cycle track alongside the railway going into Little Island and then over into Glounthsune.

Cyclists should not being going through that junction.

spacetweek wrote: »

Aren't they reattaching the previously severed old road? That would be your east-west cycle route and cyclists should be going north-south anyway since that would put them in the tunnel.

Unfortunately if you check figure 2.1.1 you'll see that cyclists and pedestrians will share a footpath and then cross the Cork-to-Dublin slip-roads which will be free-flowing traffic. When I asked about this during the consultation they said that there won't be a bridge or underpass, but since traffic will be going 50kmh it should be fine. This is what I meant when I said that it will effectively render the area unusable. More serious cyclists will likely take the 4km detour through Glanmire, whereas casual users and commuters will simply be deterred. Pedestrians are almost non-existent since the previous tunnel interchange, when no dedicated pedestrian route was provided.

I agree with you that the old road would be an ideal east-west cycle route (it's a real shame it wasn't used as such in the current layout).
I also agree that no north-south movement has ever been facilitated. Discussion on the that can definitely be facilitated elsewhere.

hans aus dtschl wrote: »

Firstly, I'm no expert, but...
Given that the current interchange design was based on figures from 2010, which predicted AADT of 67k through the tunnel by around 2031....and we've now actually surpassed that....is there anything to be said for another few minutes thought about putting in a dedicated M8 (Dublin-Cork) route on this interchange.

I just can't see how the Glanmire-Tunnel, Dublin-Cork, Dublin-East, Tunnel-East and Little Island traffic can all go through the same short stretch and all cross over each other safely.

It just seems obvious to me that the design they're building won't work.

Again, I'm not an expert.

Off the top of my head, of the 12 primary movements on this junction, only one isn’t free flow which is as you say, M8 South to N8 Tivoli.

This movement will involve going through 2 roundabouts.

Given that this is only 1/12 of all main movements, I don’t personally think it will hugely affect traffic. I also believe this is the least trafficked of all main movements.

Even at peak hours, you don’t see a huge amounts of cars doing this move.

I personally think the junction is sufficient. The tunnel being only 2 lanes will be the bottleneck, not the junction.

marno21 wrote: »

If there was only room for 11 movements free flow M8 -> N8 makes sense, as it comes to a stop about 2km further in anyway, whereas the rest flow into free flow dual carriageways.

Sean Sherlock made the excellent point on C103 yesterday that any notion of the motorway to Limerick going via Mitchelstown is out of the question as Dunkettle hasn't been designed with this flow in mind. Limerick traffic should use M40 North West quadrant if possible when built.

The main thing that needs to be in consideration with this upgrade is the effect on flow further on. The Lakeview roundabout in Midleton and Castlemartyr village are 2 areas in particular that need examining as they will be under pressure after this is done.

Most pressing concern would be Dunkettle Roundabout in my mind.

May require a flyover. In addition, redrawing of road markings before the flyover for the North Ring Road.

Agreed on M20. Dunkettle should not have more traffic forced upon it.

marno21 wrote: »

If there was only room for 11 movements free flow M8 -> N8 makes sense, as it comes to a stop about 2km further in anyway, whereas the rest flow into free flow dual carriageways.

This is sensible. My contention here is that this won't be the case for the M8-M25 slip. I believe that this will be a pinch point due to a backlog of traffic from the roundabout ahead.

Drax wrote: »

Excellent news indeed... expect it in around 10 years. :pac:

You weren't conservative enough.