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

@Chris_5339762 There is always going to be a jam when you try to put more vehicles through a roadway than it can take. That happens every morning and evening at the JLT, so the designers have to decide how to manage this jam to cause the least disruption. That’s what they did, and while it’s not nice to be stuck in there, if you remember that the point of the new interchange was to prevent a jam on one arm blocking all others, you’ll at least know why it’s happening to you...

The wide diverge is necessary to sort Little Island and M8 traffic from tunnel traffic. At the point where the lanes branch off, the mainline is four lanes. The left two lanes go into the interchange, and the rightmost other two will go over it, here:

There’s two lanes here to allow any late arrivals to move left if they need Little Island. An auxiliary lane opens about 200 m down the road for Little Island traffic to leave.

Once Little Island traffic is gone, traffic from M8 needs to be sorted out from traffic that will use the tunnel. Again, one extra lane arrives here so that M8 leavers don’t interfere with tunnel-takers.

At this point, you could bring the remaining mainline down to one lane, as it has only one destination and that destination is only one lane wide (this lane runs directly into the left lane of the JLT), but if you do that, you lose capacity on the interchange itself, which could cause traffic to back up to a point where it prevents people from leaving for Little Island and M8 further up, which brings us back to the old problem of tunnel traffic blocking people wanting to get to M8 North or Little Island West. Keeping two lanes beyond here is a buffer: it isn’t a “jam generator” so much as jam isolator: it confines the delays to the traffic stream that will use the tunnel, or does so as much as is possible.

I agree with you that the end of that lane (below) is somewhat sub-optimal. A taper should have started further back, given the average Irish driver’s bloody-minded refusal to yield to anyone on their right, but it’s imperative that there aren’t three lanes trying to merge into the centre one here, as that situation is guaranteed to cause collisions.

I suspect the original design was to use bollards or some other kind of soft divider to prevent everyone trying to pile into the centre lane at the same time, but that may have been ruled out after the planning was submitted, and now that right-hand “lane” appears to be kept as a refuge for over-height trucks:

The tunnel should be widened (and it should have been built properly in the first place but this is Ireland). What will also be needed is new flyovers at the Dunkettle interchange from the widened tunnel on to the N25 in both directions and a rebuild of the shambolic N8 mainline through the junction.

We shouldn't accept "it'll do" because this is exactly the outcome that happens. The "new" Dunkettle interchange is redundant already because of small peripheral thinking.

Yes but first we need an underground rail system with at least 50 lines, connecting all the suburbs. Then we need cycleways connecting every individual house in the city. We'll get around to widening the tunnel out to 16 lanes then.

Most school runs are a diversion of an existing parental commute, and most are at the "home" end of that commute. The ones you notice, parents dropping children at urban secondary schools, should be better handled, but they have no real impact on pinch-points further back on the journey: that person would be driving that car through there anyway.

The big drop in traffic at this time of year is due to people taking summer holidays, something that a large share of commuters cannot do while their children are in school. And as this isn't the 1950s, one family holiday often takes two cars off the road...

I've just returned after four months driving in Spain, Portugal and France. As I headed eastbound on the N40 having come from Ringaskiddy Ferry Port the advance overhead signs for the M8 certainly looked unique and unlike what I had got used to on my travels. Had I not know better from local knowledge I would certainly have been tempted to think I could access the M8 from either lane of the N40.

I did notice some lane information painted on the road before the JLT but the speed and proximity of other vehicles prevented me from actually reading the information before I passed over it.

The first indication that the only lane from which to safely access the M8 is lane 2 of the N40 was the signs at the M8 slip itself.

The new interchange was never going to address capacity of the tunnel. It can’t. The capacity of each tunnel bore is fixed, and is not going to be increased.

What the interchange was meant to do, and what it actually does very well, is isolate the effects of congestion. So, if you’re backed up going north through the tunnel, other people can now still freely access the southbound bore. When the old roundabout was in place, congestion on any arm of the roundabout basically blocked access for all routes approaching it.

Yes, this is as good as it gets - but it’s also as bad as it gets too. The problem isn’t “not enough lanes”, it’s “too many private cars”. Our next move is to move current drivers onto alternative transport options. That means train or bus (you can’t cycle through the tunnel). To be clear, I did not just say “make everyone take the bus/train” - there will always be drivers who have no other option; right now, that’s almost all drivers, so we need to start providing those options. Reducing the number of drivers who have no choice but to drive through the tunnel every morning and evening is the best bang for the buck we can do here: there will not be another tunnel bore.

I dont see how anything in the public transport arena can reduce numbers significantly enough, unless your talking about a widespread urban rail system linked to the trainstation taking in places like blarney, ballincollig, airport, douglas, ringaskiddy, carrigaline, mahon etc and thats never going to happen.

A huge portion of the traffic through the tunnel is commercial and wont ever change.

If someone is coming from east cork already and using the car then the trainline into town just dont suit their destination, an extension to youghal might help some people but of those from further afield than midleton that would use the train how many are not already driving to east cork stations parking and getting the train already?

Commercial traffic flows fine, as most of it avoids the morning and evening commuter peaks anyway. I use this road a lot: it’s only bad from 07:45 to 09:00 and then 16:30 to 17:30, Southbound is worse in the mornings than northbound; it reverses in the evening, Friday’s evening peak is about half an hour earlier than usual. But outside of those times, traffic flows freely.

But commercial traffic is only a small minority of what’s on this road. There’s only one cause here, and it’s an enormous rise in private car commuters. Nobody is choosing to do this crappy commute; they’re forced to. There are lots of reasons for this, but the biggest is that our dysfunctional housing market is forcing people to live further and further from their place of work, so people who would normally have lived within the city boundaries are now commuting from as far away as Youghal.

The point I was making is that there will be no more spent on this road: the only way to accommodate more cars is to build another tunnel bore, and that will cost the better part of a billion euro, and based on every similar intervention everywhere else on earth, within five years, the traffic jams will be back. It’s just not happening. If we’re going to spend over €500 million in Cork to reduce traffic congestion in the tunnel, there’s cleverer and more effective ways to do it than expensively kicking the can down the road for a few years.

“Better options” means better public transport in general, but it doesn’t just mean public transport. It also means providing more homes in the places where they’re needed, and where there’s better access to public transport. It’s not like all of the the people living miles away are in their dream home on a huge site: most are living in the same kind of new-build semi-D packed in a private housing estate that they couldn’t afford anywhere nearer to Cork.

Yes. Getting off topic, but the Cork Light Rail is going to be a big part of the answer here, as there's zero chance of a direct heavy-rail service into the trip magnets of Mahon, Bishopstown.

Agreed with the extra costs of another tunnel bore, but most damningly it would also require building Dunkettle interchange for a third time, and even the normally car-blind crusaders against "government waste" would object to that.

The knock on works needed to facilitate another tunnel bore would pay for a bus corridors and couple of light rail lines in the city. That's where the transport budget has to go now.

Another way I think about it is for both commuting, short or long distance traffic, just try getting from anywhere in the Cork area to anywhere else in the Cork area without going on the N40. Its next to impossible.

Yes, doing the M20 without doing the M20 - M8 link is one of the dumbest decisions currently being drawn up. And for Mr Ryan to not fund the entire north ring is an absolute joke, especially given this. You can't with any logic have freight etc from Ringaskiddy any up the west coast being routed M28 - N40 - Blackpool - M20. Its absolutely daft, and for the sake of only a few kilometers of a connection.

And no, the Northern Distributor is not an acceptable alternative.

No the P&R is planned for North Esk. I don't see the value in it, I'd prefer them to pump money into Little Island instead. By all means put in a new stop and develop in North Esk but P&R there seems wasteful.

I'm in favour of the North Ring, but not at the expense of the massive investment in urban transport. The N40 North must have few junctions. It's currently being talked about as connecting at the existing Killylough junction (Sarsfields Court), rather than Watergrasshill.

Unfortunately even if we do the North Bypass, most East Cork traffic is still going through Dunkettle, so the urban transport system is the top priority for me. The council are trying to progress the Northern Distributor project at least, so that's a start.

I want a North Bypass, a Northern Distributor and massive Cork Urban Sustainable Transport investment, but if I must pick priorities then then it's the urban transport network, then the distributor (because of the lack of housing) and then the North Bypass, in that order.

Surely there could be a P&R that uses the railway??

I'm not sure what you're both discussing, but the current P&R proposal is a surface car park at North Esk, feeding a train station there. I'm saying put the parking at Little Island and develop North Esk as an office-type employment area like Eastgate. It'd be connected by "greenway" (let's not discuss the shambolic design).

I think the P&R at North Esk is already far too far from the M8 to be of any real value. It'll only really be useful for people coming from the East. Almost nobody is coming down the M8 and going in to Tivoli now, they're all exiting at Killalough and Watergrasshill and rat running through the Northside. I see almost no value in another car park 1km away from Little Island station car park.

I'd agree that tenants of office developments outside the city want parking spaces, but they're already being refused them: see the unfortunately-named Parkplace in Eastgate! I definitely agree that it's better to encourage offices at Kent in fairness, I just don't see the value in a P&R so close to Little Island and so far from the M8. I'd sooner see one at the other side of the Interchange at the Tivoli Crosbie Transcar holding lot: it could double up as a station for the future development of the lands there. With loads of spaces free in Little Island every day I'd say of all the proposed stations in the Cork area, the North Esk one looks like one of the least useful

I think charging anything to use a P&R car park is a mistake. The recurring costs of running a car park with no tolling infrastructure are negligible, so there isn’t a whole lot to be covered, and any deterrent can have a significant effect on uptake.

• Financial: Even €1 a day adds up over a 46-week work year. It’s €230 after tax but if your marginal rate is 42% that’s approx €460 a year out of your salary when USC and PRSI are factored in.
• Convenience: Sure, we should all be chill Zen monks during rush hour, but nobody wants to queue at a barrier to get in or out of a car park, nor do they want to stand in the rain at a pay+display machine.

And any loss in revenue for Ireland Inc from not charging for the P of P&R has to be offset against the reduction in costs associated with having fewer private vehicles on our streets.

FWIW, if I was responsible for transport, I wouldn’t even be charging for the R of P&R but I know that is a bridge too far for many.

The problem with P&R, and likely the reason they've been put on the long-finger is because the second someone gets into a car they're less likely to use public transport. While all of us who drive already think that a P&R is great, the top priority is retaining the people who already use public transport: trying to get them to not buy a car.

That's again why I favour putting money into Tivoli or Little Island rather than North Esk. At both, station upgrades can make the station valuable for both P&R and non-car users.

One place where I really strongly favour a P&R though is Blarney. And a small station in Blackpool. But these will probably only start when the passing loop in Kent is done.

A P&R at Ballincollig or Glanmire would see bus passengers stuck in traffic behind cars unfortunately, so we desperately need bus priority to get full value out of them. The one at black ash works because the bus usually isn't badly held up too badly by traffic.

Anyway just keeping it on-topic, I don't see P&R as being a high priority for Dunkettle/North Esk

On the tunnel , I don't think the tunnel is the problem , it's the multiple merges just before the tunnel , ( heading south ..) pre summer In the mornings I the was going from bumper to bumper traffic on the approach to traffic starting to stretch out a bit in the tunnel , unless of course there was a crash on the n40 ,

The dunkettle interchange is the biggest traffic interchange in cork , that it was built without any thought to public transport is a bit bonkers,

So a ,city centre, ballincolig, CUH,UCC,CIT, quality rail service will make the midleton ,cobh and mallow services far more useful ,

Kind of need an effective south ring bus service too , basically dunkettle to bandon road , fast frequent,and connected to as many other transport routes as possible..

214 runs from the station to CUH these days, but 214 is not a frequent, or particularly punctual, service.

Corrected my post. I meant the 214 goes halfway to Bandon, not the 208. The route of the 214 is absolutely ridiculous. Busconnects will help with that, if the whingers would go away.

IMO the merge lane from little island , just before the tunnel , is far too long , it's a 60kph speed limit there , and then the actual merge point is just before a blind downhill turn , straight into the tunnel ,

Basically it merges where people automatically slow down ,

Had a nice gentleman in a BMW going from N25W to tunnel the other day in the overtaking lane of the slip barrel down onto the hatching, continue onwards until the lane physically disappears where it merges into the tunnel, then force his way in. Absolute clown.

Tbh, I think the Southern Orbital Distributor and Northern Orbital Distributor should be the main priorities (although in an ideal world they’d all be priorities!). Get local city traffic off the N40 and out of the tunnel. As discussed before, it’s probably causing the main capacity issues and defeats the purpose of the N40. It can’t be a bypass and distributor. However, I’d take a different approach to them than the city council’s plans - instead I’d use new roads.

The Southern Orbital Distributor could be:

Mahon Link Road - Jacob’s Island Road - new bridge across the river to Rochestown Road - Monastery Road - new road through Garryduff/Moneygurney to Ballinimlagh Road - new road to Elm Hill - Airport Road - new road to Spur Hill - new road to Bandon Road

This is mostly greenfield and provides access for those in the city commuting from suburb to suburb. They could implement heavy restrictions that prevent HGV from using it. The existing local roads could be used for bus and cyclist priority to hit the densest areas. The junctions would have to be laid out in such a way that it can’t be used as an extension of the N40, so heavy good vehicles won’t use it. I think it would be complicated but could work. Junctions could be:

Blackrock/Mahon (at R852)

Rochestown/Passage West (at R610)

Maryborough/Mount Oval (at Garryduff Rd)

Douglas (via R609)

Donnybrook/Carrigaline (at Ballinimlagh Rd/vis Donnybrook Hill & Ballinrea Road)

Grange/Frankfield (at Elm Hill/via Cooney’s Lane)

Airport/City Centre (via N27)

Leghanamore/Togher/Wilton (via Spur Hill/Sarsfield Road)

Bishopstown (via Bandon Rd or Waterfall Rd)

That way, anyone living on the southside can get to the other parts of the southside without using the N40 or local roads. This should be accompanied by the closing of N40 on ramps within the city to encourage people to use the new road. Specifically: Mahon Westbound ramp, Rochestown on ramp, Douglas Westbound ramp

Thoughts?

Without junction closures, I just can’t see a distributor road (whether it be how I laid one out, or one following the R610, R609 and R851) being used. You’re right that it would cause uproar, but I think it’ll have to happen. The N40 as it is is just way too convenient. The benefit of the one I laid out I think is that it, while goes around the southside rather than through it like the N40, it has a regional (or high capacity) connecting it to each neighbourhood. Other than the central neighbourhoods (like Ballinlough, Ballintemple, Turner’s Cross, etc), you wouldn’t need to drive through the neighbourhoods to get between them. For example, going from Mahon Point to Douglas, you’d drive over to Rochestown Road via the new bridge and down the R610. Not a major difference between driving onto the N40 and to Bloomfield. If you’re going from Dunnes in Bishopstown to Donnybrook, you wouldn’t have to get onto the N40 and navigate Kinsale Road Roundabout and go through Grange. If you’re going from Maryborough to Wilton, you don’t need to go onto the N40 and add to the Bloomfield Interchange traffic. It’s not a perfect fix by any stretch of the imagination, but it takes existing traffic and moves it to somewhere that doesn’t impact national traffic bypassing town.

They’d also need to ensure that the new road doesn’t just facilitate urban sprawl. It’s close enough to the built up city that it shouldn’t, but there would need to be strict rules preventing development south of it. This would also help prevent it from being a trip generator for trips that don’t already exist