2+2 Junctions

mk6705

Are all 2+2 junctions going to be roundabouts? I can appreciate GSJs are much more expensive...but isn't in short-sighted to have so many roundabouts on 2+2 roads? And they'll probably need to be replaced. For example, if roundabouts are the standard junction type, this means when the Adare to Abbeyfeale scheme is built (Long way off quite possibly) there will be tailbacks created at the junctions for Abbeyfeale and Newcastle West. Surely there's room for GSJs for towns at least?

corktina

nothing wrong with roundabouts...its the average clueless irish driver that causes problems

Chris_5339762

A lot of junctions will be roundabouts, but some will be compact GSJs. For instance on the New Ross bypass two of the three junctions will be roundabouts but the middle one (effectively the New Ross Interchange for passing traffic) will be a compact GSJ.

corktina

corktina wrote: »

nothing wrong with roundabouts...its the average clueless irish driver that causes problems

Roundabouts are terrible for road users with two wheels.

corktina

Dónal wrote: »

Roundabouts are terrible for road users with two wheels.

I contend it isnt the roundabouts that are terrrible, its the other users. They work perfectly well in the UK on very busy junctions with mulitple lanes in and out and around them. Such junctions would be mayhem here.

L1011

There's no reason to prevent them building GSJs, remember that this is the country that uses them relatively often on single carriageways... (I can think of about 20).

Mc Love

I'd rather have roundabouts than traffic lights tbph

veryangryman

Mc Love wrote: »

I'd rather have roundabouts than traffic lights tbph

QFT

God i hate traffic lights, especially when un-necessary. Roundabouts are fine if the traffic isnt too bad. IMO very few remaining* at grade junctions in the country couldnt be solved with roundabouts. I mean solved as in "wont create a massive tail back". Newlands about the only exception.


*Please dont mention Galway - i mean junctions without already proposed replacements

Irish and Proud

Adro947 wrote: »

Are all 2+2 junctions going to be roundabouts? I can appreciate GSJs are much more expensive...but isn't in short-sighted to have so many roundabouts on 2+2 roads? And they'll probably need to be replaced. For example, if roundabouts are the standard junction type, this means when the Adare to Abbeyfeale scheme is built (Long way off quite possibly) there will be tailbacks created at the junctions for Abbeyfeale and Newcastle West. Surely there's room for GSJs for towns at least?

AFAIK, there is a junction strategy for 2+2...

Treatment for intersecting roads as per their PCU levels:

Less than 1000 PCUs - Grade Separation with No Mainline Access;

1000 to 5000 PCUs - Compact Grade Separated Junction;

More than 5000 PCUs - At Grade Roundabout on Mainline -

If there is any situation where there's road of less than 1000 PCUs meeting a 2+2 (online section etc), a LILO may be provided to the near side once there are roundabouts within a reasonable distance in either direction - not sure what the desirable distance is though.

Hope this helps!

Carawaystick

Irish and Proud wrote: »

AFAIK, there is a junction strategy for 2+2...

Treatment for intersecting roads as per their PCU levels:

Less than 1000 PCUs - Grade Separation with No Mainline Access;

1000 to 5000 PCUs - Compact Grade Separated Junction;

More than 5000 PCUs - At Grade Roundabout on Mainline -

If there is any situation where there's road of less than 1000 PCUs meeting a 2+2 (online section etc), a LILO may be provided to the near side once there are roundabouts within a reasonable distance in either direction - not sure what the desirable distance is though.

Hope this helps!

So a busier junction will have a non grade seperated junction? only in Ireland.
:eek:

JupiterKid

It seems rather idiotic to have a policy whereby the busiest junctions with 2+2 roads will be roundabouts.

There should be as many compact GSJs as possible. I can also see roundabouts creating hassle and tailbacks where towns have their main access to their 2+2 bypasses.

I'm not really totally comfortable with the wire rope barrier dividing each carriageway of the 2+2s. They look too flimsy and are dangerous for motorcyclists. I would prefer if a concrete barrier was used instead.

Zubeneschamali

veryangryman wrote: »

Please dont mention Galway

Oh, never mind then.

Irish and Proud

Carawaystick wrote: »

So a busier junction will have a non grade seperated junction? [PLEASE DELETE]only in Ireland.[/DELETE]
:eek:

This is my take on it...

A 2+2 road is designed to carry 20k PCUs - an level that a decent roundabout is well capable of handling IMO. The junction strategy for 2+2 is probably quite similar to that on A roads in England - take the A1 (now being upgraded gradually to motorway due to largely increased traffic levels) - it was for many years a mixture of GSJs and Roundabouts (at least since the mid 1980's).

On the 2+2 roads here, I guess the NRA are striking a balance between cost and user friendliness. On one hand, they don't want to build a higher spec GSJ for the busier junctions owing to cost control, but on the other, they don't want to force too many unfamiliar motorists (which there would be a lot more of on the busier intersecting roads - visitors, tourists etc) through indirect tight slips.

Also, I guess the NRA wants to avoid continuous uninterrupted stretches of 2+2 for 10s of kilometres in order to reduce loss of concentration and excessive speed - they would probably end up being treated like motorways then - remember, there's only 8m of pavement for 2 lanes (and only a wire barrier) on 2+2 as opposed to 10.5m on the standard motorway. There's far less room for error in the 0.5m strips on each carriageway. I think the 2+2 roads in Sweden have a mixture of GSJs and Roundabouts too - certainly Roundabouts - see here!

Also, check out this PDF Document (less than 900KB) from the NRA site!

Regards!

munchkin_utd

Irish and Proud wrote: »

<snip>Also, check out this PDF Document (less than 900KB) from the NRA site!
Regards!

Indeed. See page 3, the picture of the well tight junction on a 2+2 in what looks like Sweden.
Christ, thats a tight exit. Well, its grand if you have slowed down on the mainline to 40kmh or so.
The Irish motorist expects 500m long slip roads that you can bomb along so having such short tight junctions would be a recipe for disaster.

That said, the GSJs already existing on the network like on the Cavan by pass are pretty acceptable though. Theres plenty of indication that it's a tight bend and its not quite a severe a junction as in the swedish example.

A total tangent, but the 2+2 roundabouts on the Kells By Pass got me thinking about normal national routes and the solution to dangerous junctions/ the small amount of slow traffic holding up large amounts of traffic for dozens of km! (also seen it on the big hill leaving Letterkenny for Donegal).
If the NRA slapped in some roundabouts on existing regular primary routes BUT also remoulded the road after the exit to 2 lanes for say 700m or so (aka a 2+1 or crawling lane) to allow faster traffic overtake slower (accelerating) traffic, you could eliminate some dangerous junctions AND allow faster moving car traffic overtake trucks and slower cars that ruin your journey time on longer cross country trips.

Carawaystick

at grade junctions are much more dangerous for pedestrians and cyclists crossing the mainline.

the nra could always build lay-bys to allow breaks.

The Nra could always build a deceleration lane, like are already on some two way roads, and on the N4 at the Downs in Westmeath.
or Look at what nirs are doing on the A1, grade separating the route.

veryangryman

Zubeneschamali wrote: »

Oh, never mind then.

Did you read my next sentence? There is a proposed bypass to replace the majority of the bottleneck roundabouts in the city hence why i dont count it

grogi

corktina wrote: »

Such junctions would be mayhem here.

It is not the fault of the motorist who just don't know how to behave. Roads are for people, not vice versa...

Where are proper signs telling which lane to take far before the rb? From time to time I drive through Jack Lynch tunnel and always find myself on the wrong lane just after the tunnel. There is only one (and horizontal) indication about the lanes before the tunnel...

The painted lines on the RB usually make significant percentage of the drivers confused where they should go. They are not stupid - apparently the signs are wrong.

A TV campaign explaining people the rules on the RB could be useful too.

corktina

grogi wrote: »

It is not the fault of the motorist who just don't know how to behave. .

OF course its their fault...whose else is it? Its all in the rules of the orad if they chose to follow them and there IS a tv campaign right now,

grogi

corktina wrote: »

OF course its their fault...whose else is it? Its all in the rules of the orad if they chose to follow them

Technically you are correct... But authorities can resent and blame the motorist or actually try to do something with it...

corktina wrote: »

and there IS a tv campaign right now,

I didn't know... I don't watch TV