NRA have this morning advertised for engineering consultancy to design medium to long term solution to the junction!
:):)
The lights at the current Dunkettle create an uneven distribution of traffic downstream of the interchange: the lights collect the traffic into closely-spaced platoons, with clear road between each platoon. This kind of distribution can cause congestion at lower levels than if the same number of cars were more equally spaced on the road. (A big cause of congestion delay is lane changing into small gaps; tightly packed groups of cars increase the chance of this happening)
Or, for the tl;dr - I think that traffic flow through Douglas flyover will actually improve after Dunkettle is complete, even if there’s more of it.
I don't think you are either. And I think it's very counter-productive to hope that this project or another N40 one (and then just one more N40 project ad nauseum) will fix the issues we have. This is like the M50 all over again: at a certain point we are not "expanding" our way out of this. We need modal shift urgently and we likely need to sort out the Northside. If we're seriously talking about widening Douglas, then we're just wasting our time in my opinion.
My mistake, I thought the closure was for the finishing touches on the bridges over the Dunkettle roundabout, which were featured in the close-up photos of ongoing waterproofing.
Isn't part of the solution to this the variable speed limits presuming people actually follow the speed limit. The variable message signs have already been installed, the use of variable speed limits just needs to be expanded from the M50 to the N40.
Drop the speed limit from 100 to 60 between Mahon and Kinsale Road Roundabout at peak time to slow the flow of traffic and stick a speed van on the road to ensure they are followed. Or better yet, a permanent speed camera on each gantry.
There may be an increase in traffic levels due to people no longer avoiding the junction. This isn’t the crux of the argument though.
There are big queues back up both the M8 and N25. These traffic queues will simply move on to the next choke point which will be Bloomfield / Douglas Flyover. I think it’s a possibility that queues could reach back to the tunnel in the mornings, at least at the start. People will modify their behaviour to avoid traffic by leaving earlier / later or by taking alternative routes (less likely as there are very few if any alternative routes.
So is your problem that the improved Dunkettle will increase traffic volumes?
I don’t think I am. Seeing very significant tailbacks each morning from Bloomfield is just a realistic expectation.
We were told continually in the Bandon/Sarsfield flyover thread that there would be not additional tailbacks at the Douglas flyover. This was simply incorrect.
Yeah but there is equally no point in catastrophising either.
It's the Glashaboy bridge that's getting treated I think? So there will be no Westbound connection over Glashaboy river whatsoever. I'm not fully sure what your proposed alternative routing is, but I can't see anything available other than a routing via Glanmire Bridge (L2998) which just wouldn't cope with the volumes of traffic.
From the latest news letter
A full closure of the N25 westbound will be required..................... We are currently targeting a closure from 7:30pm on Friday 21st April 2023 until approximately 9:00pm on Saturday 22nd April 2023. The main diversion route will be via the N40 and the southern ring road and this diversion route will be well signposted for the duration of the closure.
BTW, It's not the 'Southern Ring Road, it's the 'South Link Road' (N27)
Why not simply down the slip to the Dunkettle roundabout and back up the slip to the Glanmire roundabout?
Nobody is saying we shouldn't do Dunkettle. Some are saying that we should do far more!
In terms of crystal balls, we are almost all agreed that this project will not solve N40 problems. It doesn't need a genius to see. Most of us are also agreed that further N40 expansion will not solve N40 problems. We now likely need progress on N40 North and heavy investment in sustainable transport solutions.
Yep absolutely. They're effectively solving the Dunkettle interchange problem by partially routing traffic through Glanmire. I think this is not good.
I don’t think anyone is saying Dunkettle shouldn’t be done. There’s no point in people sticking heads in sand over the likely consequences though.
Good grief - the amount of doomsayers on this thread is just incredible. To listen to them we'd probably have been better off just not doing anything at Dunkettle.
Perhaps there will be issues at various points further along the routes because of increased demand although with throughput being delivered on a more even basis then hopefully some of these congestions points will ease out. In the end there may need to be futher improvements on the Cork SRR network but we can't simply deliver every single possible solution at once. Let's get Dunkettle done and see what actually happens as opposed to crystal ball gazing.
I remember we have. My idea was to remove the current westbound slip at the M28/N40 junction and continue the slip on its own bridge, next to the N40, next to the Douglas viaduct and straight into the weaving lane between Douglas and the KRR. Then throw a third lane over the KRR bridge which nicely merges into the extra lane there. Its remarkably neat, easy to build and would solve the problem completely.
I think we’ve both discussed this at length in the M28 thread. The only workable solution I think is to stack carriageways on top of each other over the Douglas flyover. And that’s never going to happen.
Ideally, you want to cap the number of cars going through any stretch of road. There is a speed which maximises capacity. Once you go above that, chaos ensues. Traffic hitting the flyover over a longer period is a much better result than traffic hitting it in a more concentrated matter. The latter is just much worse overall.
I've said that since Day 1, that the Douglas Flyover westbound will be badly jammed westbound in the mornings once Dunkettle is done - as the bottleneck will move to there.
I also fear that when the M28 is done and the bottlenecks caused by the N28 are gone, that the Douglas Flyover westbound will be one of, if not the worst bottleneck in the country with near constant jamups. I think when we get to that stage that we'll get armageddon.
The annoying thing is that one mile of widening between the M28 junction westbound, over the flyover (somehow) and to the Kinsale Road Junction would cure it. But thats going to be a very, very hard mile to widen, if ever. Don't forget the KRR bridge was built with 3 lanes westbound in mind. Its wide enough.
I don’t believe there will be additional traffic. However, I do believe the capacity of the junction will increase and so the current queues up the M8 and the N25 will be moved on to the Douglas Flyover. Hell, the queues back from the Bloomfield / Douglas Flyover could go as far back as the Dunkettle Interchange itself.
This was discussed a lot in the thread on the Bandon and Sarsfield Roundabout flyovers. In the end, traffic which was previously queued at these roundabouts got moved onto the Douglas Flyover with constant queuing there in the evenings eastwards.
What do you think will cause the extra traffic into the tunnel? The exta roundbaout that traffic from N8 -> Tivoli are subjet to? Think of the before and after for that traffic.
Before: Queue N8 southboung to meet the lights at the old roundabout. Then on the roudnabout, they were usually stopped again at red light where they meet the traffic coming out of the tunnel.
After: Free flow from N8 to first dunbell roundabout. At first roundabout they need to stop if there's traffic coming from Little Island or East going to Glanmire/East (fairly low volume I'd imagine). At second roundabout they never need to stop, only scenario would be if a vehicle leaving LI is doing a 180. Realistically that's free flow.
So they skip queing for 2/3 sets of lights to potentially stop at one quiet roundabout. I realise it's longer as the crow flies but it's going to be much faster IMO
I think the throughput into the tunnel will increase, leading to higher peak traffic on the SRR. This will result in worse traffic but for a shorter period of time each morning and evening IMO.
People on here said that the Bandon road and Sarsfield Road flyovers wouldn’t cause any additional congestion westwards on the SRR. They were wrong with tailbacks before the Douglas Flyover becoming a daily occurrence when they opened.
I think the Douglas flyover will see serious congestion when all movements into the tunnel become free flow. 8 to 9 each morning will be chaos.
I don’t think SRR will get worse eastbound, because it’s the current Dunkettle interchange that creates the delays we see now. Westbound, I don’t see much problem either - more or less the same amount of traffic will be entering the tunnel as before, only now it won’t be bunched up into platoons by traffic lights north of the tunnel.
We can’t really judge the final interchange by looking at the throughput of what is effectively a building site: when the Tunnel-to-City slip finally opens, we’ll get a better idea of Eastbound, but Westbound might have to wait until the whole thing is done..
Of course, there will be an induced demand effect when the new interchange is in place, but removing the lights at Dunkettle will increase the throughput of the interchange enough to deal with this.
(Next step is to improve public transport to avoid us being back in the same kind of congestion in a couple of years from now)
We don’t know yet how the first 2 roundabouts will look like. I’ll hold judgement on these until the junction is in its final layout.
Traffic on the SRR is going to get worse when Dunkettle becomes free flow. Much worse I’d imagine.
This is true. The rush hour tivoli route though is 3 roundabouts followed by a crawl the whole way up to town (especially if half the tivoli dual carriageway becomes bus lane). So no great option.
Out of rush hour the south ring - south link will be much less hassle to any destination beyond tivoli.
There is no way I would take that route furling rush hour. You’ll be fighting traffic at the following locations:
Suspect it would be much faster to go in the lower Glanmire road (dependent of course on your final destination.
I think for m8 - City Centre traffic the logical route becomes tunnel - south ring - south link.
Not sure if much of the traffic along the lower road/tivoli is of m8 origin/destination, but any reduction there would be a nice side effect of the convoluted m8-tivoli routing
On your last point. How else can they have this junction free flow but have 2 M8 lanes feeding into the tunnel. I don’t think it’s possible.
Queuing issues will resolve when the full junction opens.
🤣 This is a truly unhinged and laughable post. Irish people insulted as well as god and the stars talked about here in relation to a road junction. What a weirdo you are. Piss off back to some MAGA forum where you belong.
It's piss-poor design is what it is just as the intended M8-city routing is a mess.
Go East to hit 2 roundabouts and then merge back onto the inbound lane? How is that any improvement on even the current setup for that routing?
It's clear that anyone coming from the M8 is an afterthought - it's already bad enough with cars trying to skip the queue and switch lanes for the tunnel at the split at times.
The photo shows a stack.
Cloverleafs are generally not built anymore because the design results in entrance slips followed by exits which cause all sorts of weaving issues.
Stacks or partially unrolled cloverleafs are preferred. The latter is a half way house between a stack and a cloverleaf.
I believe the intended M20 - M40 junction is a partially unrolled cloverleaf.
Truly one of the more bizarre posts I’ve read on this thread. First you do some armchair psychologist thing on another poster which you then extrapolate to an entire nation. And then you display woeful ignorance of road design by saying that we need clover leaf junctions. Nobody builds them anymore because of their high land take and low safety. The junction in your photo is NOT a clover leaf.
:):)
