N40 - Cork South Ring Bandon & Sarsfield Flyovers

harry21

Outkast_IRE wrote: »

Fire them off an email asking them. Sure they should have nothing to hide.

I'm not that concerned. I think ARUP or the NRA or their consultants would have picked up on anything of concern.

starch4ser

http://issuu.com/tcmeditorial/docs/01ee2013-04-11e0?mode=window&pageNumber=1

serfboard

starch4ser wrote: »

http://issuu.com/tcmeditorial/docs/01ee2013-04-11e0?mode=window&pageNumber=1

Great photo there.

Outkast_IRE

Seen that they got another full set of beams up last night, very impressive.

BluntGuy

Passed by this a few days ago or so and was very impressed by the whole operation. Also saw a fella with a camera taking a picture at one of the junctions, wouldn't have been anyone from around here by any chance?

AugustusMinimus

Must take a drive down there tonight or tomorrow.

Are all the beams now in place ?

I fear for those central support pillars. A big fear that it will start to sink.

TheChizler

AugustusMinimus wrote: »

Must take a drive down there tonight or tomorrow.

Are all the beams now in place ?

I fear for those central support pillars. A big fear that it will start to sink.

Passing earlier it looked like it was done! The beam placement that is. I didn't realise the beams would bridge the entire gap, I thought they were just to go halfway. I'm more than doubly impressed!

run_Forrest_run

passed on the way to work this morning, the double stretch of beams looks impressive alright.

AugustusMinimus

TheChizler wrote: »

Passing earlier it looked like it was done! The beam placement that is. I didn't realise the beams would bridge the entire gap, I thought they were just to go halfway. I'm more than doubly impressed!

Indeed. After first reading about them, I thought there was two sets of pillars on the roundabout with 3 large beams being used to bridge the gap. Only 2 beams with a single pillar bridging the gap is very impressive.

neddynasty

AugustusMinimus wrote: »

Only 2 beams with a single pillar bridging the gap is very impressive.

I wonder what it'll be like in the winter when the roads are icy? With the underneath so exposed could it turn the flyover into an ice rink!?

harry21

Geogregor wrote: »

Any chance for pictures of those problems?

Taken on phone camera while in car so not great. On the Echo picture in the link above you can see the white van on the far right. They were working on the area which has sub-sided.

harry21

And the kerbing problem.

IMC042

Does anyone know if its still on track for the July 2013 opening??

neddynasty

IMC042 wrote: »

Does anyone know if its still on track for the July 2013 opening??

Yep it's still on track for the end of July opening. I think they'll make it too.

IMC042

neddynasty wrote: »

Yep it's still on track for the end of July opening. I think they'll make it too.

That's great news, it's gonna cut my 1hr 5m journey nearly in half.

Outkast_IRE

Really ? I am of the opinion that the tunnel and approach to dunkettle is going to become far worse due to this.
I think its going to increase tailbacks coming to the tunnel.

L1011

Outkast_IRE wrote: »

Really ? I am of the opinion that the tunnel and approach to dunkettle is going to become far worse due to this.
I think its going to increase tailbacks coming to the tunnel.

Unlikely, going on experience of similar on the n4 and n7. Same volume of traffic just arrives less lumpily.

IMC042

Outkast_IRE wrote: »

Really ? I am of the opinion that the tunnel and approach to dunkettle is going to become far worse due to this.
I think its going to increase tailbacks coming to the tunnel.

I get off at the kinsale road roundabout so I don't need to worry about that :-)

Outkast_IRE

MYOB wrote: »

Unlikely, going on experience of similar on the n4 and n7. Same volume of traffic just arrives less lumpily.

Will have to wait till september to find out for sure with schools back etc, hopefully the ideas that are floating about for the dunkettle will gain some momentum and a plan gets the go-ahead.

AugustusMinimus

IMO, there will be additional tailbacks at the tunnel.

While some of the traffic will come off at Kinsale and Bloomfield, the majority will continue to the tunnel. Removing the tailbacks at Sarsfields and Bandon Roundabouts will just add to it elsewhere.

neddynasty

AugustusMinimus wrote: »

IMO, there will be additional tailbacks at the tunnel.

While some of the traffic will come off at Kinsale and Bloomfield, the majority will continue to the tunnel. Removing the tailbacks at Sarsfields and Bandon Roundabouts will just add to it elsewhere.

Think I'd have to disagree. The volume of cars going to the tunnel will remain the same but the flow of cars there will change. It'll be a steady flow of strung out cars rather than the pulse type scenario we see no. The strung out flow should give the Dunkettle Roundabout a change to operate better.

I could be completely wrong but that's how i see it playing out in my head. Could be wishful thinking too!

IMC042

It seems logical to me that the tailbacks at dunkettle will be worse. Same volume of traffic all reaching the point of congestion quicker = longer tailbacks over a shorter period of time.

MrDerp

IMC042 wrote: »

It seems logical to me that the tailbacks at dunkettle will be worse. Same volume of traffic all reaching the point of congestion quicker = longer tailbacks over a shorter period of time.

No. It doesn't work like that. The system is a sequence of servers, each with their own arrival rate and service time. The throughput of the system is a function of these together. The arrival rate overall of cars to the tunnel won't be significantly increased by reducing the service time at the two upgraded junctions, it'll just be a more consistent flow rather than bursts released by the lights.

You're also assuming that all cars accessing the tunnel come through the two upgraded junctions, and/or that cars coming though the two junctions will actually continue on to the tunnel and not get off at significant population areas like Douglas, rochestown, carrigaline, Mahon etc.

The tunnel traffic might seem longer at certain very busy periods, but that will be coincidence. The number of cars being processed won't increase unless people now see it as a better option than before to take the ring road. The one thing that may happen is for peak (at the tunnel) to begin and end a little earlier

IMC042

MrDerp wrote: »

No. It doesn't work like that. The system is a sequence of servers, each with their own arrival rate and service time. The throughput of the system is a function of these together. The arrival rate overall of cars to the tunnel won't be significantly increased by reducing the service time at the two upgraded junctions, it'll just be a more consistent flow rather than bursts released by the lights.

You're also assuming that all cars accessing the tunnel come through the two upgraded junctions, and/or that cars coming though the two junctions will actually continue on to the tunnel and not get off at significant population areas like Douglas, rochestown, carrigaline, Mahon etc.

The tunnel traffic might seem longer at certain very busy periods, but that will be coincidence. The number of cars being processed won't increase unless people now see it as a better option than before to take the ring road. The one thing that may happen is for peak (at the tunnel) to begin and end a little earlier

I'm not assuming that all cars accessing the tunnel only come through these two junctions or that cars which normally get off before the tunnel would now be going through it after the flyovers are complete hence why I said 'same volume of traffic'.

Your first paragraph sort of almost made sense in my head though, but if the vehicles that are normally released in bursts are now allowed to cruise straight through to the tunnel and the lights at dunkettle still only allow the same number of vehicles through per cycle, how can that not result in longer tailbacks at peak time?

MrDerp

IMC042 wrote: »

I'm not assuming that all cars accessing the tunnel only come through these two junctions or that cars which normally get off before the tunnel would now be going through it after the flyovers are complete hence why I said 'same volume of traffic'.

Your first paragraph sort of almost made sense in my head though, but if the vehicles that are normally released in bursts are now allowed to cruise straight through to the tunnel and the lights at dunkettle still only allow the same number of vehicles through per cycle, how can that not result in longer tailbacks at peak time?

True the mean service time of the last server in your system, Dunkettle, remains the same. As does the mean service time of the road from Mahon, the Mahon interchange, the road from Bloomfield to Mahon, the Bloomfield interchange etc, and all the way back.

The change will be in the mean service time of the two upgraded interchanges. This will be lower, with the arrival rate of cars remaining the same (in theory, I. Reality more cars will be tempted to the road). The throughput of the system therefore improves.

It seems intuitive that this will increase the bottleneck at Dunkettle, but think deeper on the throughput. If that car leaving Ballincollig at 3pm on Friday gets to Dunkettle 15-20mins quicker, it is through the last server earlier before the old peak. This in fact will stretch out the peak traffic.

Arrival rates fluctuate over time, but they average out. Tailbacks build when the arrival rate is greater than 1 / mean service time, you get through quickly when it's lower. With the new system, the arrival rate will build to capacity earlier on tha Friday afternoon - the last server in the system will achieve capacity and start pushing though it's max number of cars earlier in the day.

In short Dunkettle will be busy (from the south ring side) earlier. From the perspective of the guy working in Mahon who used to sail through at 3.30, however, he will see a busier Dunkettle and complain that the problem was pushed down the road. It wasn't, it's the improved throughput getting cars to the end of the system, and through it, earlier

superhooper

As I travel this route every morning it seems to be that the junction coming from the Western side is at tipping point in the morning i.e it won't be able to handle any queueing which will have transferred from the Bandon rd/Sarsfield rd regardless of any changes in volume.

AugustusMinimus

On a closed system, this is easiest to visualize with a sand timers.

Picture 3 sand timers, stacked on top of each other. 3 squeeze points where sand has to go through at a slower rate. Each pinch point, is like a roundabout on the SRR.

Pour sand in the top. Sand will get lodged in the top part. It will slowly pour through the first pinch point. No sand will get back up at points 2 or 3 because the rate at which sand it coming through point 1 is the same as it can go through points 2 and 3.

Remove point 1 and the sand will backup at point 2. Remove points 1 and 2 and it will back up at point 3.

This obviously doesn't take account of

1. Each roundabout having slight different capacities or
2. That cars can exit or enter the SRR between the 3 roundabouts we are discussing in question.

To me, the tailbacks going east towards Dunkettle will simply have to get worse. However, as MrDerp has said, it doesn't mean it will take longer to get from Ballincollig to past the Dunkettle Interchange. However, it will probably take longer if you enter the SRR at either the Kinsale Roundabout or Bloomfield just to the backlogs now all being in front of you.

cork_south

AugustusMinimus wrote: »

However, it will probably take longer if you enter the SRR at either the Kinsale Roundabout or Bloomfield just to the backlogs now all being in front of you.

And you can add the Mahon slip road to that.

AugustusMinimus

cork_south wrote: »

And you can add the Mahon slip road to that.

Didn't include that cause the backlog is usually past that exit anyways.

The worst I remember it (without any accident happening) was about 2 years ago when the backlog came back over the Kinsale Roundabout flyover.

KCAccidental

perhaps they could programme the lights a little differently at dunkettle?