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N20 Mallow to Rathduff Pilot 2+1 Scheme

  • 04-09-2015 10:35pm
    #1
    Moderators, Entertainment Moderators, Science, Health & Environment Moderators Posts: 14,291 Mod ✭✭✭✭


    The N20 2+1 pilot scheme installed in ~2006 seems to be regarded by the NRA as a failure as there is currently major roadworks ongoing on this stretch of road concerning the removal of the wire barrier seperating the 'carriageways'.

    Whilst I knew this would happen one day, I always assumed this would happen when the M20 was being built beside it and this was becoming the alternative route. 2+1 has its pros and cons but it's best suited to lower traffic routes with infrequent junctions to provide overtaking opportunities, not a road with a very high AADT and lots of junctions meaning lots of 1+1 stretches.

    (Said I'd keep this out of the M20 thread as that should be used for discussing the actual M20, and the regular debate about whether it should shadow the N20 or not which some people won't drop)


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Comments

  • Moderators, Business & Finance Moderators, Motoring & Transport Moderators, Society & Culture Moderators Posts: 66,442 Mod ✭✭✭✭L1011


    I believe it ended up having a noticeably higher accident rate than a non divided carriageway did, as did the N24 Piltown 2+1.

    The NRAs 2+1 implementations were all incredibly poor and it could definitely have its place in certain areas, if done right - but on new or retrofit to very new build roads only, as frequent junctions and gaps in the barrier kill the concept.


  • Registered Users Posts: 739 ✭✭✭Jayuu


    L1011 wrote: »
    I believe it ended up having a noticeably higher accident rate than a non divided carriageway did, as did the N24 Piltown 2+1.

    The NRAs 2+1 implementations were all incredibly poor and it could definitely have its place in certain areas, if done right - but on new or retrofit to very new build roads only, as frequent junctions and gaps in the barrier kill the concept.

    I really think the poor implementation of the 2+1 pilot schemes was a huge loss from a development perspective. There are numerous schemes that could be done as 2+1 where the volumes don't justify full 2+2 or HQDC standard. And proper 2+1 would be better than WS2 in practically all circumstances.

    But the N24 Piltown 2+1 is a complete disaster especially driving it at nighttime (which thankfully I haven't had to do for a few years now).


  • Registered Users Posts: 19,248 ✭✭✭✭road_high


    I think they are fantastic, providing regular safe overtaking opportunities. It's just the woeful standard of Irish driving made them not work to their optimum.


  • Registered Users Posts: 4,517 ✭✭✭AugustusMinimus


    road_high wrote: »
    I think they are fantastic, providing regular safe overtaking opportunities. It's just the woeful standard of Irish driving made them not work to their optimum.

    They aren't designed to cope with the levels of traffic on the Mallow road. A lot of people for some ungodly reason seem to drop to 80 or even 70kph on the single section on the Mallow road whereas they do the full 100kph the second you go to overtake them.


  • Registered Users Posts: 4,517 ✭✭✭AugustusMinimus


    L1011 wrote: »
    I believe it ended up having a noticeably higher accident rate than a non divided carriageway did, as did the N24 Piltown 2+1.

    The NRAs 2+1 implementations were all incredibly poor and it could definitely have its place in certain areas, if done right - but on new or retrofit to very new build roads only, as frequent junctions and gaps in the barrier kill the concept.

    I don't think we'll see them again. The difference in price with 2+2 just doesn't justify 2+1.


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  • Registered Users Posts: 5,539 ✭✭✭Leonard Hofstadter


    Indeed, 2+2 is hardly any more expensive but is much safer because there's no need to speed past slowcoaches on the 2 lane bits for fear of being stuck behind them for another 2 km. It also means even on the less busy roads you'll never get held up by a slow driver, so it's quicker and much safer for hardly any extra money. Hopefully this will be the standard for any future N road that does not justify a HQDC or motorway.


  • Registered Users Posts: 739 ✭✭✭Jayuu


    I don't think we'll see them again. The difference in price with 2+2 just doesn't justify 2+1.

    My worry is that instead of 2+2 we'll get WS2 on certain roads instead. 2+1 could have been a handy compromise.


  • Registered Users Posts: 8,384 ✭✭✭Markcheese


    I don't think we'll see them again. The difference in price with 2+2 just doesn't justify 2+1.

    Could you put a dual carraigeway (2+2) on that stretch of the mallow road??

    Slava ukraini 🇺🇦



  • Registered Users Posts: 4,517 ✭✭✭AugustusMinimus


    Markcheese wrote: »
    Could you put a dual carraigeway (2+2) on that stretch of the mallow road??

    I doubt it would cost that much. However, there would be loads of at grade junctions. We don't build dual carriageway in this country with at grade junctions anymore.


  • Registered Users Posts: 5,783 ✭✭✭Chris_5339762


    Jayuu wrote: »
    My worry is that instead of 2+2 we'll get WS2 on certain roads instead. 2+1 could have been a handy compromise.

    WS2 isn't being built anymore. For any upgrades you'll either get decent S2, or 2+2 (Type 2). (or of course HQDC/Motorway (Type 1 as its known))


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  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    So they are removing the wire barrier and putting in what? I travel it everyday and saw a good few crashes in the last 3/4 months.


  • Registered Users Posts: 8,779 ✭✭✭Carawaystick


    I doubt it would cost that much. However, there would be loads of at grade junctions. We don't build dual carriageway in this country with at grade junctions anymore.

    The R132 at Dublin airport was built with at grade junctions just 2 years ago


  • Moderators, Business & Finance Moderators, Motoring & Transport Moderators, Society & Culture Moderators Posts: 66,442 Mod ✭✭✭✭L1011


    The R132 at Dublin airport was built with at grade junctions just 2 years ago

    Not by the NRA.


  • Registered Users Posts: 8,779 ✭✭✭Carawaystick


    L1011 wrote: »
    Not by the NRA.

    Chris didn't qualify who built the roads.


  • Registered Users Posts: 4,517 ✭✭✭AugustusMinimus


    I should have qualified my comment. They don't build 2+2 with at grade junctions unless signalised or roundabout based.

    Are their any unsignalised junctions on the R132 which would involve traffic crossing over 2 lanes of moving traffic in the other carriageway?


  • Registered Users Posts: 8,779 ✭✭✭Carawaystick


    Not on the new section.
    It's 4 lanes wide, 2 general traffic, 1 bus. 1 bike&walking ( which is 3m wide)


  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    They are starting to work on the N20 now! Are they widening the road? Seen them cutting down trees around 5/5.30 yesterday evening.


  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    When are the works supposed to be finished?


  • Moderators, Entertainment Moderators, Science, Health & Environment Moderators Posts: 14,291 Mod ✭✭✭✭marno21


    When are the works supposed to be finished?


    December 18th but I'm open to correction on that


  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    marno21 wrote: »
    December 18th but I'm open to correction on that

    Thanks for that.

    Are they getting rid of all the wire barriers? The second 2+1 is still been used.


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  • Registered Users Posts: 2,002 ✭✭✭niloc1951


    Just back from three months in Europe and never seen a cheese wire separation on 2+1 sections which are very common, particularly in France.

    Also what is our preoccupation with having a hard shoulder.
    I have driven thousands of kms. of road where there is no hard shoulder because where space permits it is used to provide 2+2 or 2+1 with emergency stopping places. On such sections which do not have a central divide just a continuous white line the speed limit is the same as ordinary roads.
    I understand if a driver is caught on the wrong side of attracts a summons based on dangerous driving, which probably accounts for the fact that I have never seen anyone committing the offence.

    There are 2+2 and 2+1 which do have ARMCO or a Jersey Wall separation where the speed limit is increased to 110kmh (dual carriageway limit) and these can be as short as 1km, but the increased limit permits faster/safer overtaking of slower vehicles.

    The above solutions greatly increase road capacity and provide a less stressful and safer driving environment for minimal cost.


  • Registered Users Posts: 8,384 ✭✭✭Markcheese


    Its the frequent junctions on that stretch of road that cause problems... and yes I wonder about hard shoulders especially on n roads .
    Are they moving down to do the next 2+1 stretch after christmas or is that it ...

    Slava ukraini 🇺🇦



  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    Markcheese wrote: »
    Its the frequent junctions on that stretch of road that cause problems... and yes I wonder about hard shoulders especially on n roads .
    Are they moving down to do the next 2+1 stretch after christmas or is that it ...

    That's what I'm wondering! :)


  • Registered Users Posts: 4,517 ✭✭✭AugustusMinimus


    Anyone have photos of the work done?


  • Registered Users Posts: 2,002 ✭✭✭niloc1951


    Markcheese wrote: »
    Its the frequent junctions on that stretch of road that cause problems... and yes I wonder about hard shoulders especially on n roads .
    Are they moving down to do the next 2+1 stretch after christmas or is that it ...

    What's common in Europe is where there's a junction on an 2+2 or 2+1 the road reverts to 1+1 with the centre reserved for turning vehicles.

    On such sections you may also see a layout which allows traffic emerging from a side road and turning left (right here) to execute the manoeuvre in two parts, first to a waiting lane in the middle of the road, usually a continuation of waiting lane for traffic turning left (right here) off the road, and than merging onto the through lane on the main road when there is a gap in the traffic. It means that vehicles emerging from the bye-road and turning left (right here) don't have to wait until traffic is clear from both directions.


  • Closed Accounts Posts: 2,341 ✭✭✭D Trent


    niloc1951 wrote: »
    What's common in Europe is where there's a junction on an 2+2 or 2+1 the road reverts to 1+1 with the centre reserved for turning vehicles.

    On such sections you may also see a layout which allows traffic emerging from a side road and turning left (right here) to execute the manoeuvre in two parts, first to a waiting lane in the middle of the road, usually a continuation of waiting lane for traffic turning left (right here) off the road, and than merging onto the through lane on the main road when there is a gap in the traffic. It means that vehicles emerging from the bye-road and turning left (right here) don't have to wait until traffic is clear from both directions.

    If you've taken a trip to Belfast recently you'll have seen this as soon as you bypass Newry


  • Moderators, Entertainment Moderators, Science, Health & Environment Moderators Posts: 14,291 Mod ✭✭✭✭marno21


    Looks like I was wrong, they seem to be putting the posts back in for the wire barrier on the resurfaced section now


  • Registered Users Posts: 752 ✭✭✭TheBigGreen


    Is there more road works early in the new year?


  • Registered Users Posts: 6,048 ✭✭✭Truckermal


    Is there more road works early in the new year?

    Ya they are doing up to Rathduff I was surprised to see the wire up again..


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  • Moderators, Entertainment Moderators, Science, Health & Environment Moderators Posts: 14,291 Mod ✭✭✭✭marno21


    It was just a resurfacing, barrier replacement and drainage addition scheme. I didn't notice anything wrong with the surface before, considering all the traffic chaos it caused over the last 4 months. Not sure if many here drove it at night but it's possibly the most difficult drive I ever did at night with the constant cones and steel barrier along with the narrow twisty lanes for the 4 months.


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