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Retrofitting wide single carriageways to 2+2

  • 31-10-2022 12:32pm
    #1
    Moderators, Entertainment Moderators, Science, Health & Environment Moderators Posts: 14,297 Mod ✭✭✭✭


    I have posted plans in the N2 Ardee-Castleblayney scheme of the preliminary design of that particular scheme. 31km of 2+2 mainly overlayed on the existing widened singlecarraigeway, with 5 new grade separated junctions, routing of all accesses to parallel access roads and the joining up of all local roads which interface with the N2 (removing access to the N2 but not hampering local movements), also featuring an upgrade to 2+2 of the Carrickmacross bypass (from 2+1) and the upgrade of the GSJs and roundabouts on that bypass. It is mainly an online upgrade but there are brief offline sections where the online routing would be deficient or has too many accesses on it.


    IMO this is an excellent blueprint for several upgrades around the country. We have several stretches of national primary route where there are long stretches of 80s/90s offline/partially offline wide singlecarriageway and towns and villages dotted in the middle. Upgrading the existing alignment, while providing full local movements around the existing route is an excellent method of saving on earthworks, land purchase and saves having 2 engineered route corridors unnecessarily duplicated. It has massive safety benefits alongside the standard connectivity benefits. It has been successfully used on the N4 for 3km outside Collooney and is proposed for the N4 Carrick-on-Shannon to Dromod project also. It also seems to be included in the M20 project on the southside


    I can think of several projects where this is feasible and would provide cost savings and better value for money, some of these are suggested in possible routings


    N4 Mullingar-Longford

    N17 Knock-Collooney

    N24 Cahir-Waterford

    N25 Midleton-Youghal 


    Besides the above, there are several stretches not proposed for upgrade where such improvement schemes would be cheap on a per km basis and would improve the functionality and safety of the road network



    N3 Virginia-Cavan

    N4 Castlebaldwin-Carrick on Shannon

    N5 Turlough-Charlestown

    N13 Stranorlar-Letterkenny

    N15 Bundoran-Ballyshannon

    N17 Tuam-Claremorris (reuse the existing improved sections with short bypasses of Milltown and Ballindine)

    N17 Claremorris-Knock

    N21 Rathkeale-Newcastlewest

    N21 Castleisland-Abbeyfeale

    N22 Farranfore-Tralee

    N24 in Co. Limerick (improved sections required from Limerick to Boher and in parts between south of Boher and Brookes Bridge)

    N25 Youghal-Dungarvan

    N25 Lemybrien-Kilmeaden

    N25 New Ross-Wexford

    N33 Ardee-M1


    What are yer thoughts? Would a 2+2 retrofitting project be a meritorious endeavour in addition to the planned new routes?



Comments

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


    Double post



  • Registered Users Posts: 3,473 ✭✭✭roadmaster


    Did TII not plan to this and call them Expressways but it never happened for some reason



  • Registered Users Posts: 1,311 ✭✭✭KrisW1001


    @roadmaster - they are planning this, and as new Primary schemes pop up, they are increasingly being designed as 2+2, so it's happening.

    The creation of new "Expressway" signage for 2+2 roads was only a suggestion, and nothing more has happened. Given that there are two long stretches of 2+2 opening in the next year, and not a peep about "Expressways", I think it won't be done.

    --

    On the first list, I can comment on N25, as I know it very well:

    Wexford to New Ross needs no improvements. Nearer Rosslare will be addressed by the M11/N25 Oilgate-Rosslare scheme, but once you get to Wexford, traffic is extremely light all the way to New Ross: this is really not a busy road.

    From New Ross to Kilmeaden is already upgraded or being upgraded. After this, though, immediately to the west of the Waterford Bypass there is about 2km of bends and dips that would rule out any online widening.

    The Kilmacthomas Bypass section of Lemybrien-Kilmeaden was planned with a widening to 2+2 lanes in mind (but not the current standard), although I think one or two bridge supports may need to be reworked slightly to accommodate the wider road under it. (The existing right-turn junctions for Stradbally and Mahon Bridge could be reworked into a left-in, left-out pair, connected by the old N25 that runs north of the road here).

    West of Lemybrien and up to the start of the proposed Dungarvan bypass, online widening could be difficult in places, due to the terrain: especially the sweeping bend just west of Lemybrien itself

    After this, there's really no need for most of Dungarvan-Youghal to be upgraded - it's an extremely quiet stretch of road. The one section that does need improving, from the end of Youghal to Kinsalebeg (where the wider road begins) cannot be done on-line.

    Youghal-Midleton is a clear candidate for online 2+2: bypassing Killeagh and Castlemartyr would actually follow the general line of the existing road, which takes a turn into both places.

    Really, for most of N25 between the two cities, a wide single carriageway is fine, and a better use of money would be to grade-separate the junctions (leaving room for a road widening in future if it's ever needed, of course).

    We seem to have a blind spot here about the idea of having single-carriageway roads with a limited number of junctions, all grade-separated, but this is commonplace in other countries: that's what I'd like to see done first.



  • Registered Users Posts: 6,544 ✭✭✭Pete_Cavan


    After a quick look at the N2 Ardee-Castleblayney preliminary design posted by Marno in the relevant thread earlier, my first thoughts were much the same as Marno's above and was going to reply along similar lines. I think the age of entirely offline new build roads is at an end, partly due to the difficulties it involves (planning, environmental, etc.) and also that when the inter-urban motorway is complete, the remaining projects don't justify the cost.

    I totally agree that there needs to be more of a focus on integrating the existing road where possible. It most likely will require more design work but should make the project less likely to fall foul of NIMBYs or environmental objections. From a brief look at the N2 proposed design, existing houses/businesses and the local roads can all be connected up with a bit of careful consideration. A well placed and designed GSJ can provide a good opportunity to connect up bits and pieces either side of the new dividing road.

    I think there was an opportunity to incorporate c.3km of the existing road at the eastern end of the Virginia Bypass project. Instead the proposal is for full on offline build through some hilly terrain. The existing road between the existing RAB at the end of the current 2+2 and Mullagh is wide and straight with few houses/businesses along the northern side. I think objections on environmental grounds are more likely to succeed if there has been no mitigation of building through open countryside.



  • Registered Users Posts: 5,503 ✭✭✭veryangryman


    Green policies (not just from the party of that name) are choking anything remotely car centric, even where public transport will never be improved.

    A good sneaky way of cutting public expenditure but penny wise pound foolish of course.



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  • Registered Users Posts: 38 Imeacht gan teacht ort


    I agree, this is very well thought out and the best way forward, in my opinion.



  • Registered Users Posts: 8,548 ✭✭✭SeanW


    N4 Mullingar-Longford

    Can't speak to the others but I don't think this one is a candidate for online conversion, or at least I hope not. There are three reasons why an offline build as proposed is best:

    1. There are private houses and other accesses all over the route, as well as frequent intersections with L roads.
    2. An offline build would provide bypasses for 3 villages, Rathowen, Ballinalack and Newtownforbes.
    3. Not all of the current route is WS2, for example between Longford and Edgeworthstown.

    It would not be as easy as repainting the road and putting cheese grater wire down the middle.



  • Registered Users Posts: 6,544 ✭✭✭Pete_Cavan


    L roads and certain private houses have to be linked with parallel roads. There are certain houses which would have to be bought out, many of which are 60s/70s bungalows which might not be inhabited beyond the current occupant anyway. See the N2 project for how they propose to deal with these issues.

    The bypasses of the villages goes without saying, 100% online upgrade is not being proposed. Also, regardless of the existing road type, substantial works are required anyway, it wouldn't simply be relining the road.

    I think it is going to be increasingly difficult to build new long distance offline roads going forward. The evidence is there already. The environment is going to be given increasing priority, including over individual homeowners. Simply ripping 50km of new road through the countryside is going to find it very difficult to survive the courts. Ploughing on regardless like they did in Galway is not going to give a satisfactory conclusion.



  • Moderators, Business & Finance Moderators, Motoring & Transport Moderators, Society & Culture Moderators Posts: 66,471 Mod ✭✭✭✭L1011


    N15 Leitrim/Sligo border -> Donegal Town; and pretty much all of the N4 with some limiting bypassing.



  • Registered Users Posts: 3,473 ✭✭✭roadmaster


    Earlier this year i spoke with one of the engineers involved with the N3 Virginia Bypass and asked him why they did not try to retro fit some of the existing sections as it it is very wide in parts.

    He told me they done a cost excercise and the amount of extra side roads to allow access to existing propertys would blow the budget also they belived it was a lot simpler and less hassle to do a greenfield route



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  • Registered Users Posts: 3,031 ✭✭✭hans aus dtschl


    You're absolutely right, some sections of these N roads are also double-jobbing as L roads.

    No problem with the concept but they'd need to provide plenty new L roads. Midleton to Youghal is affected by this also. You possibly end up with such additional land-take that you'd be as well off doing a totally new offline 2+2 in some places!



  • Registered Users Posts: 6,544 ✭✭✭Pete_Cavan


    I can't see how that could be the case between the end of the existing DC and Maghera. There are mainly only properties along the southern side of the existing N3 and a Type 3 SC could be retained for them (potentially being an extension of the R194, along with the existing N3 through Virgina).

    On the northern side of the road, there are only properties at Whitegate Cross and the L7106. For Whitegate, the L28245 (off the existing roundabout) could easily be extended to the L3021, thus linking it to the wider road network. The L7106 could be extended westwards and tie in to the existing N3. A new N3 along there would have to swing north at that point anyway to go around Maghera so the existing carriageway will be available for reuse.

    That would involve reusing half the existing carriageway on the southern side of the road and two <500m L road extensions on the northern side.



  • Registered Users Posts: 3,473 ✭✭✭roadmaster


    I Agree but he said they looked at it and it could not be done



  • Registered Users Posts: 14,561 ✭✭✭✭loyatemu


    drove the N25 from New Ross to Cork earlier this week and for a lot of it I was thinking "they could fit 2+2 in here". I hate the super-wide single carriageways, they encourage weaving and risky overtaking, driving in the HS etc.

    There would have to be provision for pedestrians and cyclists though - personally I hate cycling on N roads but currently you can use them. Ideally with 2+2 they should provide an alternative route parallel and ban cycling on the 2+2 itself.



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


    Its harder than it looks to do 2+2 on the Kilmacthomas bit. Theres a lot of local access and small junctions. I don't think it would stand up to a cost-benefit very well, although it would be nice. Just to me, it looks a lot harder than you might think.



  • Registered Users Posts: 1,311 ✭✭✭KrisW1001


    Under the current rules, a 2+2 cannot be built without a dedicated cycle and pedestrian way being put in place alongside; that also goes for online upgrades.



  • Registered Users Posts: 739 ✭✭✭Jayuu


    It's an interesting thought but realistically there would probably be a huge amount of logistical problems such as current access from houses on the routes not to mention many of them which already go through towns and so would either have to be bypassed.

    The one I would be most familiar with is the N24 Cahir to Waterford road and realistically trying to retrofit this without bypassing Clonmel (properly), Kilsheelan, Carrick-On-Suir and Mooncoin would be impossible. It probably would be much easier to design and build from scratch.



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


    Ah but does that mean "built" or "retrofitted".



  • Registered Users Posts: 6,423 ✭✭✭zg3409


    On these wide roads even a passing pane here and there would be a big improvement.

    I used to drive all over the country mainly on national roads and crazy overtaking and getting stuck behind a car for 30+ minutes was common.

    I am not sure it would reduce road deaths as dual lanes people tend to drive fast rather than being stuck, but it would help with journey times.

    I thought at the time this was proposed years ago the reason it did not happen was they wanted to put the money into new roads. I wonder was the real reason was the money would go to painting the roads only, and not into big flashy projects and possibly more work/involvement of engineers compared to a painting only exercise.

    I find safe overtaking lanes great particularly on uphill sections.



  • Registered Users Posts: 7,784 ✭✭✭munchkin_utd


    >I used to drive all over the country mainly on national roads and crazy overtaking and getting stuck behind a car for 30+ minutes was common.

    totally. My quick and easy solution to that would be to add a roundabout with a 2+1 / climbing lane exiting it for places with dangerous junctions . At a stroke you eliminate a dangerous junction and you give people a chance to overtake a slow truck or car.

    Theres many examples abroad (I think also in NI) plus the odd one in Ireland like the Cavan by-pass . Somewhere like the Tullamore by pass would lend itsself perfectly to it, rather than a full scale 2+2. It is so frustrating to see those empty yellow hard shoulders where in the odd place a climbing lane would be much more appropriate.



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  • Registered Users Posts: 1,311 ✭✭✭KrisW1001


    2+1 roads will not be built anywhere in Ireland anymore. The pilot schemes that were built were carefully monitored, and they were found to be no safer than the wide single carriagways they replaced: the collisions moved to the end of the "2" sections, as drivers attempted to recklessly overtake "just one more" car before the road narrowed.

    Also, with hard-divided climbing lanes, you are now preventing a downhill driver from overtaking a slow-moving vehicle, even if there is no uphill traffic at all. That kind of restriction can push drivers into dangerous behaviour once the road widens.

    The big factor against 2+2 is that it is not significantly more expensive than 2+1.



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