N20 Mallow to Rathduff Pilot 2+1 Scheme

marno21 · 04-09-2015 11:35PM #1

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)

L1011 · 05-09-2015 02:54AM

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.

Jayuu · 05-09-2015 06:14PM

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).

road_high · 05-09-2015 10:42PM

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.

AugustusMinimus · 06-09-2015 08:55AM

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.

AugustusMinimus · 06-09-2015 08:57AM

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.

Leonard Hofstadter · 06-09-2015 05:55PM

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.

Jayuu · 06-09-2015 07:11PM

AugustusMinimus wrote: »

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.

Markcheese · 09-09-2015 03:48PM

AugustusMinimus wrote: »

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??

AugustusMinimus · 09-09-2015 07:52PM

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.

Chris_5339762 · 10-09-2015 07:51PM

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))

TheBigGreen · 15-09-2015 07:59AM

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.

Carawaystick · 15-09-2015 02:04PM

AugustusMinimus wrote: »

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

L1011 · 15-09-2015 02:15PM

Carawaystick wrote: »

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

Not by the NRA.

Carawaystick · 16-09-2015 09:56AM

L1011 wrote: »

Not by the NRA.

Chris didn't qualify who built the roads.

AugustusMinimus · 16-09-2015 12:18PM

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?

Carawaystick · 16-09-2015 02:26PM

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

TheBigGreen · 01-10-2015 10:45AM

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.

TheBigGreen · 23-11-2015 12:05PM

When are the works supposed to be finished?

marno21 · 23-11-2015 03:31PM

TheBigGreen wrote: »

When are the works supposed to be finished?

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

TheBigGreen · 23-11-2015 04:04PM

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.

niloc1951 · 27-11-2015 11:31AM

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.

Markcheese · 27-11-2015 02:55PM

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 ...

TheBigGreen · 27-11-2015 03:49PM

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!

AugustusMinimus · 27-11-2015 04:32PM

Anyone have photos of the work done?

niloc1951 · 27-11-2015 06:30PM

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.

D Trent · 28-11-2015 01:15AM

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

marno21 · 02-12-2015 05:52PM

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

TheBigGreen · 21-12-2015 05:06PM

Is there more road works early in the new year?

Truckermal · 21-12-2015 08:47PM

TheBigGreen wrote: »

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..

marno21 · 22-12-2015 02:26AM

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.

N20 Mallow to Rathduff Pilot 2+1 Scheme

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