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N2 - Slane Bypass [planning decision pending]
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Chris_5339762 wrote: »Yeah S2 is just a standard 2 lane road.
Not to question the engineer, but the NRA have said that it costs 10% more to build Type 2 DC (4 lane carriageway) over Type 3 (2+1, 2 lanes in one direction, one in the other). So 8% to go from S2 to Type 2 DC just doesnt add up
Meath Co Co have a VERY wide standard for S2 for national primaries and associated routes. Take a look at the Dunboyne Bypass (which is an R road) for instance.0 -
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WRONG. A 2+1 has no hard shoulders, whereas an S2 does. The cost of building a 2+1 over an S2 is therefore negligable, as the difference in width is negligable if there even is one. So your (counter)argument is back to square one.
Reduced S2 has a pavement width of 8m, standard S2 12.5m and Type 3 DC 13m. Reduced S2 is good enough for the Slane bypass because most of the road either side of the bypass is of that standard anyway. So your (counter)argument is back to square one.You do if traffic levels warrant it. Also, as I said before, there is a need to avoid under-specing the bypass so that it doesn't become irrelevant as the old Enfield Bypass on what is now the R148 has become.
That would suggest you are also in favour of upgrading the entire N2 to DC, or at least from Ashbourne to Slane. How can you not see the madness of building a DC parallel to, and within 10km of, an existing motorway which has already cost the taxpayer over a billion euro. Now you want to replicate it!
So we need two motorways and a DC within a 16 mile corridor. It is this idea of retaining and upgrading all national primary routes and shadowing the existing roads that has seen us waste hundreds of millions of euro building over spec'd roads to serve every one horse town in the country. We would have saved a fortune and have a complete motorway network now if we redrew the national primaries. The idea that Slane needs a DC bypass because it is a national primary route is ridiculous.You do if traffic levels (for whatever reason) warrant it.
As has been pointed out, 86% of the traffic on the N2 between Ashbourne and Collon is local traffic and therefore the road should be detrunked as it is not of national importance. There is not going to be an explosion in population in Ashbourne or Collon any time soon so reduced S2 is good enough.Dual carriageways are safer. The cost differential between S2 and 2+2DC is marginal. The only reason not be use 2+2 is either an extreme need for cost savings, or as you have displayed, opposition on some questionable point of principle.
The arguments about DC being safer are irrelevant as the DC section is only 3.5km long and you will have 20km of S2 at either end of the bypass. Again you are back to upgrading the entire N2 if you want to make the road safer (and by which logic every road we build should be at least DC). The issue here with regard to safety is the steep descent on approach to the existing bridge. S2 bypass provides another bridge so problem solved, no need to go to DC.0 -
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You would only use Reduced S2 if the road was to carry a small amount of traffic and if the whole N2 South of Ardee were due to be imminently detrunked. Neither, to my knowledge, is on the table. So we're back to Standard S2 vs. 2+2DC.Pete_Cavan wrote: »Reduced S2 has a pavement width of 8m, standard S2 12.5m and Type 3 DC 13m. Reduced S2 is good enough for the Slane bypass because most of the road either side of the bypass is of that standard anyway. So your (counter)argument is back to square one.
I am NOT in favour of this (though I have no objection in principle) provided that a case can be made for it. I.E. traffic levels would have to make that case, by exceeding best practice for a single carriageway.That would suggest you are also in favour of upgrading the entire N2 to DC, or at least from Ashbourne to Slane.
To be clear, I'm only in favour of building the Slane Bypass as DC for the moment.How can you not see the madness of building a DC parallel to, and within 10km of, an existing motorway which has already cost the taxpayer over a billion euro. Now you want to replicate it! So we need two motorways and a DC within a 16 mile corridor.
Without evidence of further need for DC treatment on the N2, the only thing I would do with it would be to provide a Grade Separated Junction at the Northern end of the M2, so that N2-Dublin traffic wouldn't have to bother with that roundabout.
However the road remains of significant importance if it is heavily used.As has been pointed out, 86% of the traffic on the N2 between Ashbourne and Collon is local traffic and therefore the road should be detrunked as it is not of national importance.
You couldn't be more wrong - with 20 km of S2 at each end a 3.5km section of 2+2 would give anyone stuck behind a slowpoke a chance to overtake in comfort and safety. It was in the "post IMF road design standards" thread that we should consider intermixing sections of 2+2 with mainlines of S2.The arguments about DC being safer are irrelevant as the DC section is only 3.5km long and you will have 20km of S2 at either end of the bypass.
I'm in favour of building bypasses to good specifications so that it's use becomes a no-brainer for through traffic. I am simply sounding a note of caution that cheaping it out might lead to an Enfield Mark II, where the R148 (old N4) bypass is actually slower than going through the town. Your plan risks doing precisely that, for at least some traffic.Again you are back to upgrading the entire N2 if you want to make the road safer (and by which logic every road we build should be at least DC). The issue here with regard to safety is the steep descent on approach to the existing bridge. S2 bypass provides another bridge so problem solved, no need to go to DC.
I believe that bypasses should be built to a convincing standard. What happens to the rest of the road is irrelevant.0 -
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