M17/M18 - Gort to Tuam [open to traffic]

m17

AugustusMinimus wrote: »

I still think Rsthmorrisey is the most stupid junction design ever. An incredibly costly design which isn’t free flow. A partially unrolled cloverleaf could have been built for less cost and a smaller land take.

Other countries would just automatically have put a stack here. But this is Ireland where junctions are an afterthought.

This would have been a better option but it would be to advanced for the Irish driver

AugustusMinimus

m17 wrote: »

This would have been a better option but it would be to advanced for the Irish driver

A good junction but suffers from weaving issues as the entrances from the loops come before exits to the motorway.

A partially unrolled cloverleaf does away with these weaving issue. A stack is even better.

AugustusMinimus

AugustusMinimus wrote: »

Turn it into a turbo Roundabout? Any easy solution. Still should have done this junction properly day 1 though.

Not exactly what I was thinking, but interesting.

I was thinking of simply having two lanes between entry and exit slip roads where vehicles turning right can mover to the inner lane and those that already done the 270 degrees can slip into the left and exit.
No give way markings on the left lane and the left lane removed from the roundabout after the exits and before the next entry.

Like a rotary

Sam Russell

Deleted User wrote: »

Not exactly what I was thinking, but interesting.

I was thinking of simply having two lanes between entry and exit slip roads where vehicles turning right can mover to the inner lane and those that already done the 270 degrees can slip into the left and exit.
No give way markings on the left lane and the left lane removed from the roundabout after the exits and before the next entry.

Like a rotary

All vehicles entering the roundabout (except those that are lost) are going 270 degrees. Therefore, the lane getting the 'Give Way' has to cross the lane coming from the right to get into the inner lane, and traffic coming from the right in the left lane should be exiting at the next exit. There is not enough room, and the angle of approach is too tight for it to work as freeflow if there is a lot of traffic.

A better design would have the entry road go under the roundabout road and join it from the other side (that is in the inside of the roundabout. It would require four small bridges - bit late now.

Looking at the diagram in the above post (#9094) Cars entering at A would be going to L, and would pass under the road C-I and join at I from the inside of the roundabout.

m17

Pics around annagh hill 17/05/18

Sam Russell

Sam Russell wrote: »

All vehicles entering the roundabout (except those that are lost) are going 270 degrees. Therefore, the lane getting the 'Give Way' has to cross the lane coming from the right to get into the inner lane, and traffic coming from the right in the left lane should be exiting at the next exit. There is not enough room, and the angle of approach is too tight for it to work as freeflow if there is a lot of traffic.

A better design would have the entry road go under the roundabout road and join it from the other side (that is in the inside of the roundabout. It would require four small bridges - bit late now.

Looking at the diagram in the above post (#9094) Cars entering at A would be going to L, and would pass under the road C-I and join at I from the inside of the roundabout.

I added the image after writing the text, but still it would work all drivers move to the right first then move to the left as they approach their exit.

Sam Russell

Deleted User wrote: »

I added the image after writing the text, but still it would work all drivers move to the right first then move to the left as they approach their exit.

I had written mine before I saw your picture.

If you enter the roundabout, you must cross the lane in front of you which has traffic coming towards you, exiting at the next exit, plus traffic on the inner lane exiting at the exit after that.

If you were to enter the roundabout from inside the roundabout, then you do not cross any lane and you 'spin out' of the roundabout. It would require you to pass under the roundabout through a non-existent bridge.

Oh well, they might get it right next time.

AugustusMinimus

Given that all movements on the Roundabout need to only facilitate 270 degrees I thought there may have been scope to have some movements facilitated by going anti-clockwise with the 2 lanes on the Roundabout separates with a barrier.

Don’t think that would work either without additional grade separation.

Charles Babbage

AugustusMinimus wrote: »

Other countries would just automatically have put a stack here. But this is Ireland where junctions are an afterthought.

If this was in Britain it would be dual carriageways meeting at roundabout.
This is not a very busy junction.

AugustusMinimus

Charles Babbage wrote: »

If this was in Britain it would be dual carriageways meeting at roundabout.
This is not a very busy junction.

Why design an over complex 3 grade junction when a probably cheaper one with less land take would have provided more capacity?

Would you pay more for a similar house which has more rooms than the other?

This junction does everything and it isn’t very complex.



Only 3 bridges required and yet all movement are free flow. 2 corners take very little land due to the shape.

Sam Russell

AugustusMinimus wrote: »

Given that all movements on the Roundabout need to only facilitate 270 degrees I thought there may have been scope to have some movements facilitated by going anti-clockwise with the 2 lanes on the Roundabout separates with a barrier.

Don’t think that would work either without additional grade separation.

Apart from confusing the natives, it would not work. You have forgotten the other traffic entering the roundabout.

AugustusMinimus

Sam Russell wrote: »

Apart from confusing the natives, it would not work. You have forgotten the other traffic entering the roundabout.

Indeed. Too many movements to cater for.

Sam Russell

AugustusMinimus wrote: »

Why design an over complex 3 grade junction when a probably cheaper one with less land take would have provided more capacity?

Would you pay more for a similar house which has more rooms than the other?

This junction does everything and it isn’t very complex.



Only 3 bridges required and yet all movement are free flow. 2 corners take very little land due to the shape.

Some tight turns but it would be better than the actual result we got.

AugustusMinimus

Looking at that junction, I don’t think it would take very much to upgrade rathmorrissey to something similar.

flazio

Any reason why the merging lanes West bound are kept separate while all the others bottle neck before merging? That for me is the bigger issue. The slowing and yielding I can live with, no worse then passing through a toll gate.

m17

M18 junction 16 gort

M18 junction 17 kiltiernan

M18/m17/m6 junction 18 rathmorrissy

M17 junction 19 annagh hill

M17 junction 20 tuam

D Trent

http://connachttribune.ie/tii-identifies-site-for-galway-motorway-telecommunications-infrastructure/

" – Transport Infrastructure Ireland is working with the telecommunications industry to identify suitable sites close to Galway’s motorway network.
An infrastructure site has been identified as part of this process and work is currently being progressed."

Kermit.de.frog

m17 wrote: »

M18/m17/m6 junction 18 rathmorrissy

Surely it would have been cheaper and better to build a free flow cloverleaf here?

Typical Ireland. Half assed.

m17

D Trent wrote: »

http://connachttribune.ie/tii-identifies-site-for-galway-motorway-telecommunications-infrastructure/

" – Transport Infrastructure Ireland is working with the telecommunications industry to identify suitable sites close to Galway’s motorway network.
An infrastructure site has been identified as part of this process and work is currently being progressed."

The two phone masts along the m18 rinnraheen

marno21

Kermit.de.frog wrote: »

Surely it would have been cheaper and better to build a free flow cloverleaf here?

Typical Ireland. Half assed.

They wanted to tack a MSA onto the roundabout hence that design

It's ok for now as the roundabout is lightly used.

roadmaster

Ciaran Cuffe from the green party was on newstalk before lunch and he made a snide remark about the department of transport throwing money at motorway between two towns we never heard off. I presume he is talking about Gort/Tuam. and not Cork/Limerick Its easy to see with remarks like that why the Green Party will remain a party of non importance

Sam Russell

roadmaster wrote: »

Ciaran Cuffe from the green party was on newstalk before lunch and he made a snide remark about the department of transport throwing money at motorway between two towns we never heard off. I presume he is talking about Gort/Tuam. and not Cork/Limerick Its easy to see with remarks like that why the Green Party will remain a party of non importance

Well, he has a point. It would have been a better decision to 'throw' money at the M20 rather than the M17/M18. I think everyone has heard of Cork and Limerick.

roadmaster

Sam Russell wrote: »

Well, he has a point. It would have been a better decision to 'throw' money at the M20 rather than the M17/M18. I think everyone has heard of Cork and Limerick.

There of course is need for the M20. But his comments smack of To Hell or Connacht and hence why there party is in non existence apart from one or two urban areas

Sam Russell

roadmaster wrote: »

There of course is need for the M20. But his comments smack of To Hell or Connacht and hence why there party is in non existence apart from one or two urban areas

I do not think it was the Green Party that 'threw' the money at the M17/M18 instead of the M20.

roadmaster

i dont understand your point. I know they didn't fund it, if it was up to them there would be no roads built. The Gort to Tuam serves a purpose and it is a good thing it was built.

Sam Russell

roadmaster wrote: »

i dont understand your point. I know they didn't fund it, if it was up to them there would be no roads built. The Gort to Tuam serves a purpose and it is a good thing it was built.

But not as good a thing as building the M20. I live in Dublin so it does not affect me, but the idea that building the M17/M18 should take precedence over the M20 is just preposterous.

I assume there was a political reason behind it since were projected to cost the same. Anyway, it is now built and is very welcome by those that use it.

Cookiemunster

Sam Russell wrote: »

But not as good a thing as building the M20. I live in Dublin so it does not affect me, but the idea that building the M17/M18 should take precedence over the M20 is just preposterous.

I assume there was a political reason behind it since were projected to cost the same. Anyway, it is now built and is very welcome by those that use it.

The M20 was projected to cost around €800m if IIRC. The M17/18 coat around €550m. Also the M17/18 managed to get through planning before the recession. The M20 didn't. So not really building one instead of the other, more building the one that was shovel ready.

serfboard

Cookiemunster wrote: »

more building the one that was shovel ready.

This plus 1000.

Any gobdaw knows that the M20 was (or should have been) higher priority than the M17/18 - and this is from a daily M17 user.

The real question to ask is - why wasn't the M20 shovel ready?

Sam Russell

Mod: Can we leave discussion of the M20 to the M20 thread.

The M17/M18 is built now, and no matter how much it cost or how much the M20 should have been built first, it makes no difference.

Kevwoody

Sam Russell wrote:

Mod: Can we leave discussion of the M20 to the M20 thread.

Your the one who specifically mentioned the M20 in this thread!
Just because some posters disagree and raise the valid point the M17/18 got through planning before the cuts, doesn't mean you should put on your Mod hat and end the discussion.