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

I cant see how you get from m8 coming from dublin into the city centre.

vince wrote: »

I cant see how you get from m8 coming from dublin into the city centre.

You'll have to use the dumbbell to the right of this render.

vince wrote: »

Thats a long way round but no other solution I suppose. Looks great I wonder when this gets moving.

Yes, I would have thought that particular traffic movement would have taken priority, i.e., it being the main access point to the city upon arrival. It's a little cumbersome to be expecting people to dog-leg out to Little Island, and then back-track into town. The last thing that we would want to see happening would be for traffic to shoot straight through the tunnel, and use the KR Interchange to get into town instead, applying even more pressure here.

Anyway, moan aside, it is absolutely fantastic to see this being 'fast-tracked', and they have done a great job otherwise in what is admittedly a very tight amount of space. Let's hope this move along quickly, and that it opens up development to the south, at the Port/Ringaskiddy etc., considering the existing planning precedent that has seemingly been set.

AugustusMinimus wrote: »

I was initially very much against the M8 to Lower Glanmire Road movement.

However, in the grand scheme of things, this movement will probably take up less than 10% of the total movements at this junction. The dumbbell which this movement will entail will be perfectly capable of taking the traffic load for this movement even at rush hour I suspect.

Considering this is the only mainline movements which will be required to go through the dumbbell, that's not bad at all.


In the grand scheme of things though, the Kinsale Roundabout should have had this treatment done also. There was plenty of room out there to do a slip road style setup which would have sorted a lot of problems. As it is, the queue down airport hill can be terrible at rush hour

The light sequencing is terrible at the Kinsale Roundabout. The green from both the airport hill and grange road doesn't necessarily coincide with a green to get onto the roundabout. Then there is only a 4 car turn at the light to get onto the roundabout. So traffic is just being put into a holding pattern between the two lights (Grange rd, and roundabout).

I can see where they are coming from, as it's clearly to prevent traffic backing up onto the N40 in either direction but it really is a mess.

The first thing I'd do, however, would be to make the exit for Old Kinsale Road to be exit only. Traffic trying to push across 4 lanes here and get to the N40 West causes a lot of problems at any time of the day, and is downright dangerous as they regularly
1. Get into the N40 East only lane and force their way around the roundabout in the outside lane (I get cut off on my way to Frankfield all the time), then
2. Stop dead in that lane trying to force there way across the airport lanes to get to N40 West

It's incredibly frustrating and if it's a truck/bus pulling this stunt the roundabout can get clogged even with low traffic volumes.

It's not outlandish for traffic to head towards the P&R and join the south link to access the roundabout. I do this myself to get to Grange Rd, regularly, as trying to push across 4 lanes of the roundabout is tricky unless its quiet and you can time it between light changes.

They also, I would imagine, want to leave the Lower Glanmire Road for traffic coming from the east, and encourage traffic going down the M8 continue along the South Ring and access via the N27.

Edit: My design was still far, far better though.

Junction Movements

cargo wrote: »

Is the fact that you need to go through 2 RA's to get from M8 to City not going to be a huge drawback to those designs? I'm not from the area but I do travel through this junction from time to time and its normally this movement I take. Or am I just overly worrying. Will this detour be fine once all the other traffic is taken off this movement?Will these RA's have slip for left turns at least?

I wouldn't worry too much. All of the other mainline movements will be done via slip roads.

The only mainline movement not being done by slip road is the M8 to Lower Glanmire Road. The way I think about it, is those 2 roundabouts are facilitate that one movement and exit and entry to and from Glounthaune and Little island.

Traffic going into and out of Glounthaune and Little Island won't be big. For the most part, people going from M8 to Lower Glanmire Road won't have to stop very often at those roundabouts as traffic on them will be so low. Even at rush hour I suspect.

AugustusMinimus wrote: »

Anyone like to guess btw when we'll see construction start on this. Would late 2014 be too soon ?

I would say so, between finalizing CPO, progressing the tender process etc. Assuming funding were to come through immediately (wishful), I'd say the best we could hope for would be preliminary works contracts maybe in the second half of next year; fencing, siting investigation etc...

The more I look at their design, the more that the M8S - N25W (Dublin to Cork) movement is irritating me. A simple third level on the design and they could plop this movement in. Whether they are trying to keep the whole thing to two levels I'm not sure but looking at it, there is plenty of room. It really is beginning to seem to me to be a very stupid idea.

csd wrote: »

I'm guessing that they want to send city-bound traffic via the South Link rather than the existing route via the Glanmire Road. It's the only plausible explanation I can think of.

/csd

This has been discussed in the previous pages; I really don't think that's the reasoning, considering the LGR is the much shorter, existing and most obvious entry route to the city from the M8, although I can see why you would suggest it. The South Ring is already under pressure, roundabout aside, and in particular the Kinsale Road Interchange, which would be part of the alternative route, so I don't think the plan is to exacerbate this.

I think it's really down to cost-benefit considerations, and working within a very onerous site, both topographically and area-wise. Simply, it seems like something had to give without incorporating a third tier, which would have vastly increased the cost, and probably isn't feasible anyway when the plan is to utilise the existing overbridges.

I have to admit that I was a little perturbed when I saw this movement myself, but it remains to be seen whether it actually is an issue for drivers. It might turn out to be less of an inconvenience than it seems right now.

AugustusMinimus wrote: »

IMO, they clearly do not want traffic entering into the city via the South Link. Would cause excessive traffic at both the Kinsale Roundabout and the end of the South Link Road at Eglington Street.

As others have said, an extra grade separation may have increased costs dramatically. The way I view the junction is that there are 12 main movements and a number of other movements in regards to Little Island and Glounthaune.

Of the 12 main movements, 11 will freeflow. So 1/12 main movements will have to go through both roundabouts. In addition, another 1/12 may use the roundabouts to access Little Island and Glounthaune.

All in all, I would think about 10% of the traffic will be using those roundabouts. Even at peak traffic, I doubt there will be more than 3 or 4 cars queueing at each one.

If a the commuter populations develop further in the Watergrasshill/Rathcormac/Fermoy area and the two roundabouts do cause issues during morning peak time then the residents of Sallybrook and Glanmire better get ready deal with their villages becoming part of a 'rat-run'

phatmanwc wrote: »

the M8-Lower Glanmire Road movement will have priority over these movements on both roundabouts, and shouldn't be affected by them.

This is the key point. M8 to Lower Glanmire has priority over all others movements at the roundabouts and so traffic should still flow well through them.

On this basis, I really don't think there should be an issue here. I'd imagine the junction was designed to ensure this movement was given priority on both roundabouts.

Considering irish ten year paper is <2.5% today,
its hard to see how a ppp could provide better value for money.