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Are carriageway widths on Irish motorways narrower than those in the UK?

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  • 12-04-2010 1:43pm
    #1
    Closed Accounts Posts: 583 ✭✭✭


    Although I think that the new Irish motorway network is fantastic and a great engineering achievement, I can't help but notice that the carriageway widths seem to be narrower down there. When driving on any of the new motorways it seems as if lanes, and the hard shoulders especially, aren't as wide as those on our somewhat still-born network in Northern Ireland. I can't believe that I've imagined this so are there any engineering documents that show this to actually be the case?

    I'm not talking about the new narrower central reservations but the actual lane and hard should widths.

    One thing that brought this slight contrast home to me was a drive I made on Saturday. I was over in the East and had some spare time so drove the A1/N1 from Banbridge to Dundalk to see how the Newry bypass was coming along. North of Newry the 'upgraded' LQDC (Low as in central reservation crossovers, private entrances, etc.) has lane widths of the usual dual carriageway spec up here; the hard shoulders seem to be the same width as the lanes.

    However, what's really interesting is that as you continue south onto the last section of A1 the spec. seems to change, and not just from LQDC to HQDC. The road much more resembles those in the Republic with single lane slip roads, dumb bell interchanges, etc. But in addition, there's a noticeable – well, to me at least – narrowing in the lane widths and even more so in the hard shoulder. This means that as you eventually cross the border, apart from signage, there's virtually no change in the carriageway appearance.

    One difference is in the single lane slip roads. The design of these in the Republic has always concerned me slightly. This revolves around the fact that they've only one lane and yet have just a narrow strip to the left instead of a hard shoulder. I've always wondered what would happen if an articulated lorry broke down on one of these. How would anyone get past? This thought has obviously occurred to the Roads Service as well. One of the areas where the Newry bypass, etc. hasn't gone completely with the NRA spec. is in the single lane slips. Instead of the narrow strip these have a full hard shoulder. This would seem to resolve the potential problem of a truck breakdown but I can't say that it's ideal either. It looks aesthetically awkward; why didn't they go for two full lanes? The inside one could have acted as a shoulder in the event of a problem.

    http://www.boards.ie/vbulletin/showthread.php?p=63346880 : the first of the pics in Furet's post on this page shows the slip road layout I'm referring to.

    Anyway, does anyone know why the NRA went for the narrower lanes and shoulders? Was it to do with land take costs? Given that the Irish network is mostly four lane instead of the six across much of England, and that land values were probably considerably lower even in the boom, was this really necessary? Maybe it has nothing to do with costs: did they just decide that UK specs. are needlessly wide? I think that hard shoulders are certainly narrower in France and Germany.

    Finally, my own view is that I do prefer the extra width, particularly where you're pulling out to pass an artic. I don't know but it just seems that where you've got the extra room everything seems a little less bunched up and less stressful. But maybe that's because I've transitioned between the two. I suppose if you drive exclusively down there it probably seems fine.



    Just one last observation from this drive: the explosion in one-off houses in the immediate border area. This seems to get even worse once you're into Louth. I drove around the Cooley peninsula and the thing is now just one vast low density housing estate - there's no break in the housing between towns! This gave the tourist map-picture sign in Carlingford a somewhat tragic and unwittingly ironic appearance. It shows a peninsula consisting of green countryside with distinct towns and villages. Err, that's not what I experienced. If you want unspoilt rural scenery in Ireland these days... get a ferry ticket to Wales.:(


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Comments

  • Registered Users Posts: 3,110 ✭✭✭KevR


    I think most Irish motorways have a driving lane width of 3.5metres while UK motorways have 3.75metre lanes. Hard shoulders/emergency lanes are also wider on UK motorways - 3.3m as far as I know. Irish emergency lanes are 2.5m (anyone confirm?) on narrow medians.

    The M50 has lanes which are slightly narrower than the typical Irish motorway lane width - this is part of the reason why the M50 has a 100kmh speed limit, the other reason being sight lines.


  • Closed Accounts Posts: 583 ✭✭✭MT


    If the lane widths are narrower, then this pic (http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Suir_RiverBridge_looking_south%28Edit%29.jpg/800px-Suir_RiverBridge_looking_south%28Edit%29.jpg) of the Waterford bypass would seem to show how much narrower again the hard shoulders are in comparison to those up here. That is, if there isn't a difference in spec. between HQDCs and full motorways.

    Would an articulated lorry fit into those in an emergency without forcing traffic in the inside lane to pull out somewhat?

    Ps, just posted this while KevR was answering my question.


  • Moderators, Science, Health & Environment Moderators Posts: 4,977 Mod ✭✭✭✭spacetweek


    Yes, they are narrower, 3.5 versus 3.75 metres.

    My understanding is that the UK ones were considered to be needlessly wide - they are certainly wider than in most countries where I have the information (e.g, USA is 12ft which is 3.65 m).

    Costs wouldn't be much of a factor most of the time as the land is cheap rural tracts.

    For example, the M4/M6 Dub-Galway I believe cost a billion for 200km. If you added 25 cm to each lane:
    An extra 25x4 = 1 metre;
    1 x 200,000 = 200000 sq.m = 50 acres.
    At around €10k/ac, that's an extra 500 grand
    ...which is a cost increase of 0.05% - negligible.


  • Banned (with Prison Access) Posts: 25,234 ✭✭✭✭Sponge Bob


    spacetweek wrote: »
    = 50 acres.

    Acres are IMPERIAL you dweeb, use Hectares in future Pedant :D


  • Closed Accounts Posts: 6,093 ✭✭✭Amtmann


    This image of the M8 Cashel to Cahir section, taken in August 2008, shows how wide the emergency lane is.

    https://us.v-cdn.net/6034073/uploads/attachments/71931/60215.jpg


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  • Closed Accounts Posts: 3,010 ✭✭✭Tech3


    AFAIK the spec is 2.5M,3.5M,3.5M where 2.5M is the hard shoulder on type 1 dual.


  • Registered Users Posts: 7,476 ✭✭✭ardmacha


    The spec was changed, new build is indeed 3.5m. Mind you the roads built recently in the South have little enough traffic for the most part and might have been built as an S2 in the North.

    But was the M1 not built at 3.75m?


  • Registered Users Posts: 232 ✭✭Heartbreak Hank


    Furet wrote: »
    This image of the M8 Cashel to Cahir section, taken in August 2008, shows how wide the emergency lane is.

    https://us.v-cdn.net/6034073/uploads/attachments/71931/60215.jpg

    Did that guard chase the car down on foot?? No squad to be seen.

    Surely he should have a siren on his hat though.


  • Registered Users Posts: 260 ✭✭csd


    UK spec for rural motorways is 3.65 or 3.70m running lanes and a 3.3m hard shoulder.

    See here: http://www.standardsforhighways.co.uk/dmrb/vol6/section1/td2705.pdf on page 25 of the PDF.

    Irish spec is 3.5m running lanes and 2.5m hard shoulder. The Irish DMRB is locked up in a Windows executable here, so tough luck if you have a Mac or don't run Windows.

    /csd


  • Registered Users Posts: 997 ✭✭✭Colm R


    Would the reason why the A1, just north of the border follows the Irish standard be because it was actually built as the same scheme as the N1/M1 just south of the border?


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  • Registered Users Posts: 21,436 ✭✭✭✭Alun


    csd wrote: »
    The Irish DMRB is locked up in a Windows executable here, so tough luck if you have a Mac or don't run Windows.
    It's just a self-extracting zip archive and any self respecting archive utility on any platform (e.g. Stuffit Expander for Mac) will just treat it as such.


  • Closed Accounts Posts: 1,735 ✭✭✭Irish and Proud


    KevR wrote: »
    I think most Irish motorways have a driving lane width of 3.5metres while UK motorways have 3.75metre lanes. Hard shoulders/emergency lanes are also wider on UK motorways - 3.3m as far as I know. Irish emergency lanes are 2.5m (anyone confirm?) on narrow medians.

    The M50 has lanes which are slightly narrower than the typical Irish motorway lane width - this is part of the reason why the M50 has a 100kmh speed limit, the other reason being sight lines.

    AFAIK, the UK specs for motorway dimensions are:

    3.30m for Hard Shoulders
    3.65m for Driving Lanes
    0.70m for Median Strips
    Total Pavement (D2): 2 x 11.30m

    The specs for Irish narrow median D2 motorways are:

    2.50m for Hard Shoulders
    3.50m for Driving Lanes
    1.00m for Median Strips
    Total Pavement: 2 x 10.50m

    The specs for Irish wide median D2 motorways are:

    3.00m for Hard Shoulders
    3.75m for Driving Lanes
    1.00m for Median Strips
    Total Pavement: 2 x 11.50m

    The lane widths for the M50 upgrade are 3.50m with 2.50m Hard Shoulders.

    As a matter of interest, the specs for standard Irish S2 roads are:

    2.50m for Hard Shoulders
    3.65m for Driving Lanes
    Total Pavement: 12.30m

    and 2+2

    0.50m for Verge Strips
    3.50m for Driving Lanes
    1.50m for Central Median
    Total Pavement: 16.50m (divided by wire barrier)

    Regards!


  • Closed Accounts Posts: 583 ✭✭✭MT


    If the reduction in costs from opting for the narrower lanes and shoulders on the narrow median D2s was negligible, then why do it? Surely, all things being equal the extra space is preferable. Yes, ultimately if you went for lanes in the order of something like 4.5m wide it could encourage sloppy driving. But when the UK's system is seen to work why bother reinventing the wheel? Especially if the changes you're making could actually be disadvantagous.

    When you think of all the artics, buses, larger vehicles, etc. I would have been loath to tamper with a proven design by scaling things down. Definately not when it's going to cost you pretty much the same. Maybe there aren't problems, and it's turned out fine, but designing the untried and untested can't be done with hindsight.

    What amounts to almost a meter off the hard shoulder makes them seem really tight. In fact, you're almost left with the impression that the NRA actually have doubts too given the considerable strip of aggregate poured in along their edge. It's almost as if there was a discussion along the lines of...

    "Them UK shoulders are too wide"
    "Yeah"
    "So we'll knock a metre off"
    "Er, right"
    "D'you know, they look a bit tight now come to think of it"
    "Hmm..."
    "Sure make up the difference with gravel at the edges and set the armco barriers back a bit"
    "hmmmmm...."

    Could this not give rise to a situation where an artic finds itself in difficulty, wants to pull in, but weary of the constricted space slows done somewhat in the running lane first?


  • Closed Accounts Posts: 583 ✭✭✭MT


    Here's a pic from wikipedia of the M1 in Northern Ireland: http://upload.wikimedia.org/wikipedia/commons/6/6e/M1_Moira_%281%29_-_geograph.org.uk_-_195736.jpg
    Just looking across from the white van on in the left carriageway - just coming to the entry slip - gives an indication of the shoulder width. If anything, they seem to be slightly wider than the running lanes. Any time I've driven on this road the shoulders do seem very broad.

    But compare those to the shoulders in the pic Furet links to (https://us.v-cdn.net/6034073/uploads/attachments/71931/60215.jpg)
    The difference is remarkable. Those shoulders look so undersized by comparison. I wonder if concerns over that lack of width prompted the decision to go for a band of gravel instead of a kerbed finish. I mean, if the width was possibly going to be a problem the last thing you'd want at its edge would be a row of kerbs. It would be even more hazardous to pull into in a rush.

    Again, I can't see why you would go for less if there's really nothing in it costwise.


  • Registered Users Posts: 7,476 ✭✭✭ardmacha


    The point is not that they've scaled down the UK design, but that they have expanded it. In the UK these roads would not be motorways but all purpose DCS with some separation at junctions, something like the A4 from Dungannon to Ballygawley. Such roads have only a 1m strip at the side, NRA roads have 2.5m.


  • Closed Accounts Posts: 583 ✭✭✭MT


    That's true in comparison to similarly populated regions of the UK but if you look across Europe many smaller countries have opted for an interurban 'motorway' network as extensive as those in their larger peers, regardless of the size of the cities involved.

    It's sort of like an essential service that must be provide no matter how scaled down things become. Sort of the same way that a rural hospital might be overstaffed and resourced for the population it serves in comparison to one in Dublin. A basic threshold of personel and facilities that have to be provided for the thing to function almost regardless of the population served.

    If the country could afford it I still think Ireland would have a motorway connecting Dublin to the second city Cork, even if the latter had a pop. less than 100,000. Compare that to Madrid and Barcelona, London and Birmingham, etc.

    I suppose it's an argument why the smaller the country the greater the inefficiency and lack of economies of scale. But then there must be advantages as most of Europes wealthiest countries are the smallest.

    But anyway, back to my main point. Why downgrade the design in exchange for no real cost reduction?


  • Closed Accounts Posts: 6,093 ✭✭✭Amtmann


    Well, the interurbans aren't remotely extravagant, and one must always remember that AADT was never the sole reason for their construction. Improved journey times and road geometries, increased safety and town bypasses were also significant considerations.


  • Closed Accounts Posts: 583 ✭✭✭MT


    Yeah, when you consider safety, quality of life in bypassed towns, etc. a greater share of the reason for building falls within the essential service sphere.

    However, I was just flicking through the net to see how the narrowness of those new D2 shoulders seems to compare with elsewhere in Europe. I'm only going on pics but could they be some of the narrowest?

    Looking at Autosnelwegen.nl, the shoulders there seem to be as wide as the running lanes. Here are some pics, the A35: http://www.autosnelwegen.nl/asw/pics/fotowedstrijd/feb08-01.jpg
    On the A12 the 2nd inside shoulder might be slightly narrower: http://www.autosnelwegen.nl/asw/pics/fotowedstrijd/nov08-01.jpg
    But here: http://www.autosnelwegen.nl/asw/pics/fotowedstrijd/apr09-03.jpg and here: http://www.autosnelwegen.nl/asw/pics/fotowedstrijd/jan08-06.jpg they seem to be a similar width.

    Just looking at the pics of other networks, I wonder is the trench of gravel, seemingly augmenting the shoulder width, unique to Ireland?


  • Registered Users Posts: 1,241 ✭✭✭baalthor


    MT wrote: »
    I suppose it's an argument why the smaller the country the greater the inefficiency and lack of economies of scale. But then there must be advantages as most of Europes wealthiest countries are the smallest.

    You may have answered your question in an earlier post. Most (if not all) of the smaller countries are highly urbanised.

    I also wouldn't be so sure that land acquisition costs are higher in the UK than in Ireland. In 2001* average agricultural land prices were higher in Ireland than most parts of Europe including England, Scotland and Wales (but not Northern Ireland!). Prices paid for agricultural land acquisition during road projects were often well in excess of the average, according to this NRA document. I don't think this had any bearing on the lane width however.

    *See end-notes in pdf doc.


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


    MT wrote: »
    However, I was just flicking through the net to see how the narrowness of those new D2 shoulders seems to compare with elsewhere in Europe. I'm only going on pics but could they be some of the narrowest?

    Just looking at the pics of other networks, I wonder is the trench of gravel, seemingly augmenting the shoulder width, unique to Ireland?

    As I understand it, Swiss has started building new dual carriageways with no hard shoulders, we have here too but with no laybyes to break down in unlike the swiss.

    Spanish shoulders are fairly narrow as are their lanes.

    The outside of French shoulders is usually a storm drain and is usually half a metre or so below the surface of the road, preventing a broken down vehicle moving further out of the way, unlike the gravel here.

    Have you any evidence of wide shoulders being empirically better? or narrow shoulders being worse? What ifery isn't a great point to hang an argument on.

    I'd be much more concerned with the low quality of motorway exits and entrances and junctions to be honest. Very short merges seem in fashion at certain parts of the network in Dublin anyway. I've only personal experience of drivers not merging correctly due to an inabillity to see enough to merge at the N4E-M50S and M50E-M1N; and just incompetence at M1E-M1N


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  • Registered Users Posts: 1,105 ✭✭✭nordydan


    There's a school of thought that UK specifications are too tight, seems to be a common view over on SABRE. I'd say the ROI motorway specs are about right.

    From driving in Italy last year (Sicily), I seem to remember that the lanes were very narrow compared to Irish, ahem, motherways. Not sure if the Sicilian specification is narrower than mainland Italy, or if the Mafia took their cut of the tarmac! (awaits horses head in bed...)


  • Registered Users Posts: 19,018 ✭✭✭✭murphaph


    I think the specs are fine in the south.

    The M1 in the north (and the vast bulk of the UK network) was built at a time when it was relatively common for vehicles to break down, hence wider shoulders etc. As already mentioned, the Swiss now see no point in providing continuous shoulders on new build motorways as vehicles so rarely break down in a way which leaves them unable to limp to the next emergency layby (every 500m I believe).

    It's similar to the tendency in many countries away from emergency phones as it's now expected that people will carry a mobile.

    The lanes in Ireland feel, if anything, as wide or wider than here in Germany anyway. Perhaps ths UK should be looking at amending its design standards, which, IMO are tight tight and lead to roads being designated as all purpose when they'd be motorways anywhere else.


  • Closed Accounts Posts: 2,468 ✭✭✭BluntGuy


    The Irish lanes always felt good and wide to me. The only thing that ever made the road feel narrow was the proximity of the central concrete barrier, but you get over that very quickly.


  • Closed Accounts Posts: 6,093 ✭✭✭Amtmann


    Did that guard chase the car down on foot?? No squad to be seen.

    Surely he should have a siren on his hat though.

    He waved it down having clocked it well in advance. They're often there half way between Cashel and Cahir (junction 9 and 10), hiding at the emergency access lanes.


  • Moderators, Business & Finance Moderators, Motoring & Transport Moderators, Society & Culture Moderators Posts: 67,948 Mod ✭✭✭✭L1011


    MT wrote: »

    But anyway, back to my main point. Why downgrade the design in exchange for no real cost reduction?

    The lane width was only one factor in a series of changes to the design which deliver a noticeable saving.

    Lane width, narrow median, narrower shoulder = quite a bit less land take, narrower cuttings, smaller enbankments, smaller over and underbridges. All add up, especially when building a few hundred KM.


  • Moderators, Science, Health & Environment Moderators Posts: 4,977 Mod ✭✭✭✭spacetweek


    MT wrote: »
    Just looking across from the white van on in the left carriageway - just coming to the entry slip - gives an indication of the shoulder width. If anything, they seem to be slightly wider than the running lanes. Any time I've driven on this road the shoulders do seem very broad.

    But compare those to the shoulders in the pic Furet links to (https://us.v-cdn.net/6034073/uploads/attachments/71931/60215.jpg)
    The difference is remarkable. Those shoulders look so undersized by comparison.
    No, I'm not feeling like there was any need for us to have wider shoulders.
    MYOB wrote: »
    The lane width was only one factor in a series of changes to the design which deliver a noticeable saving.

    Lane width, narrow median, narrower shoulder = quite a bit less land take, narrower cuttings, smaller enbankments, smaller over and underbridges. All add up, especially when building a few hundred KM.
    Good point and it only came to mind just there. When I made my calculations above about the saving on land, I forgot that knocking ~1 metre off the width would also result in changes to the bridges and cuttings. Of course this could all add up to a lot over a long distance.
    I think the removal of hard shoulder space was justified as a wider one wasn't necessary and it looks like there may have been a big saving after all.


  • Banned (with Prison Access) Posts: 25,234 ✭✭✭✭Sponge Bob


    spacetweek wrote: »
    I forgot that knocking ~1 metre off the width would also result in changes to the bridges and cuttings. Of course this could all add up to a lot over a long distance.

    About 6.5 x Cunnigham Acres per Statute Mile of Motorway :D


  • Closed Accounts Posts: 478 ✭✭wellbutty


    We need wider hard shoulders here for all the people that insist on having a picnic/leak at the side of the motorway :mad:


  • Moderators, Business & Finance Moderators, Motoring & Transport Moderators, Society & Culture Moderators Posts: 67,948 Mod ✭✭✭✭L1011


    wellbutty wrote: »
    We need wider hard shoulders here for all the people that insist on having a picnic/leak at the side of the motorway :mad:

    No, we need to issue good drivers with shotguns.


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  • Registered Users Posts: 10 Storm2


    MYOB wrote: »
    No, we need to issue good drivers with shotguns.

    And so, in the wake of the Batman shootings, some bright spark suggests we issue shotguns to drivers. I think I need to inspect your brain. :rolleyes:


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