Short Sections of DC for Overtaking

JupiterKid

Given the severely straitened times we are in fiscally and that there appears to be far less funding available for roads than previously, should we be entertaining the idea of building short sections of Dual Carriageway on some sections of our National primary (and Secondary) network that would afford overtaking opportunities?

It has been shown that driver frustration due to "platooning" of a row of cars behind a slow driver can lead to dangerous overtaking and head-on collisions. Indeed, many commentators have attributed the welcome fall in fatal road accidents in recent years to the new motorways which have replaced S2 routes which saw a lot of fatal head-on accidents.

Given that much of the National primary network that has not been replaced by motorways is wide S2, perhaps some sections could be widened to allow short (say, 2km or 3km) sections of DC which would allow for safe overtaking of slow traffic?

These sections would have a central concrete barrier, only LILO junctions and no crossover junctions for safety reasons.

In the UK, especially in England, there were a number of roads which had short D2 sections built in the 1960s for overtaking purposes even though they were replaced by motorways just a few years later.

Thoughts?

GerardKeating

JupiterKid wrote: »

Given the severely straitened times we are in fiscally and that there appears to be far less funding available for roads than previously, should we be entertaining the idea of building short sections of Dual Carriageway on some sections of our National primary (and Secondary) network that would afford overtaking opportunities?

It has been shown that driver frustration due to "platooning" of a row of cars behind a slow driver can lead to dangerous overtaking and head-on collisions. Indeed, many commentators have attributed the welcome fall in fatal road accidents in recent years to the new motorways which have replaced S2 routes which saw a lot of fatal head-on accidents.

Given that much of the National primary network that has not been replaced by motorways is wide S2, perhaps some sections could be widened to allow short (say, 2km or 3km) sections of DC which would allow for safe overtaking of slow traffic?

These sections would have a central concrete barrier, only LILO junctions and no crossover junctions for safety reasons.

In the UK, especially in England, there were a number of roads which had short D2 sections built in the 1960s for overtaking purposes even though they were replaced by motorways just a few years later.

Thoughts?

That's kind of what the 2+1 roads were for, but one tended to get dangerous overtaking/speeding where the roads narrows back to 1 lane..

Irish and Proud

JupiterKid wrote: »

Given the severely straitened times we are in fiscally and that there appears to be far less funding available for roads than previously, should we be entertaining the idea of building short sections of Dual Carriageway on some sections of our National primary (and Secondary) network that would afford overtaking opportunities?

It has been shown that driver frustration due to "platooning" of a row of cars behind a slow driver can lead to dangerous overtaking and head-on collisions. Indeed, many commentators have attributed the welcome fall in fatal road accidents in recent years to the new motorways which have replaced S2 routes which saw a lot of fatal head-on accidents.

Given that much of the National primary network that has not been replaced by motorways is wide S2, perhaps some sections could be widened to allow short (say, 2km or 3km) sections of DC which would allow for safe overtaking of slow traffic?

These sections would have a central concrete barrier, only LILO junctions and no crossover junctions for safety reasons.

In the UK, especially in England, there were a number of roads which had short D2 sections built in the 1960s for overtaking purposes even though they were replaced by motorways just a few years later.

Thoughts?

I don't have time to go into much detail tonight, but I do think there's a lot to be said for what you're suggesting. Even when the M1 Balbriggan bypass was built (opened in 1998), road deaths in the area declined, I think even on the adjacent non-bypassed sections - as you said, I think frustration was a large part of the problem. I don't think that 2+1 roads are really comparable as the 2 lane sections happen to be far too short (from what I heard) to sufficiently alleviate frustration.

Sponge Bob

I went into great detail on this very topic a year or two back ...so search the forum for " Interstitial "

Irish Steve

Might work, but would need a ban on HGV's doing overtake stunts on short sections of DC, otherwise the HGV would be the only one to get past the front vehicle. We already see the issue on the motorways, how many times have you seen a queue of cars held up by 2 HGV's slugging it out with each other for 2 or 3 kilometers with next to no speed differential between them. The annoying aspect of that is the rules of the road ban HGV's from Lane 2 where the speed limit is above 80 Kph, but its another of those rules that seem to be ignored more than they are enforced.

corktina

Irish Steve wrote: »

Might work, but would need a ban on HGV's doing overtake stunts on short sections of DC, otherwise the HGV would be the only one to get past the front vehicle. We already see the issue on the motorways, how many times have you seen a queue of cars held up by 2 HGV's slugging it out with each other for 2 or 3 kilometers with next to no speed differential between them. The annoying aspect of that is the rules of the road ban HGV's from Lane 2 where the speed limit is above 80 Kph, but its another of those rules that seem to be ignored more than they are enforced.

In that case you would also need an outside lane ban on Nissan Micras, elderley persons, L drivers, middle age females, persons on the phone, bloody minded arseholes, clapped out diesel vehicles in need of new injectors,et al.

antoobrien

It'd be unworkable unless there were at least two 2-3km stretches every 10km (in one direction) because of the concerns outlined in a few posts.

And at that rate of going, you'd be better off with DC.

munchkin_utd

A suggestion I made in a separate thread was the possibility of having a short stretch of 2+1 leading out of roundabouts where trucks and slow moving cars can be easily overtaken by folks who can accelerate that bit more speedily.
Its on the odd section in Ireland already where there's a climbing lane (Cavan N55 ByPass) and its also to be seen in the UK and the continent in various places.

To implement it on current roundabouts in Ireland with existing approaches with hard shoulders would cost very little (a few signs and realignment of road markings) and would eliminate a lot of what you term platooning which is proven to be a cause of major frustration leading to road casualties and fatalities.

You could even extend the idea to putting roundabouts on junctions with major Regional or Secondary roads which then both removes the danger of cars/ trucks parked in the middle of the road waiting to turn right and for folks travelling longer distances gives the opportunity to overtake slower traffic on the mainline exit

antoobrien

munchkin_utd wrote: »

To implement it on current roundabouts in Ireland with existing approaches with hard shoulders would cost very little (a few signs and realignment of road markings) and would eliminate a lot of what you term platooning which is proven to be a cause of major frustration leading to road casualties and fatalities.

Just so long as you're aware that on many of the older road surfaces (10yo or more) the hard shoulder is not paved to the same standard as the road, so it would require more than just repainting the lines. The N17 between Galway & Claregalway had to be resurfaced 3/3 years ago because they put in some right turn queues in the middle of the road, using the existing hard shoulder for mailine traiffc - causing the shoulder to start collapsing. I've seen the same on stretches of the old N6 and a few other roads.

munchkin_utd wrote: »

You could even extend the idea to putting roundabouts on junctions with major Regional or Secondary roads which then both removes the danger of cars/ trucks parked in the middle of the road waiting to turn right and for folks travelling longer distances gives the opportunity to overtake slower traffic on the mainline exit

Don't mention that in the galway city forum, you'll start roundabout war 10.

corktina

munchkin_utd wrote: »

A suggestion I made in a separate thread was the possibility of having a short stretch of 2+1 leading out of roundabouts where trucks and slow moving cars can be easily overtaken by folks who can accelerate that bit more speedily.
Its on the odd section in Ireland already where there's a climbing lane (Cavan N55 ByPass) and its also to be seen in the UK and the continent in various places.

To implement it on current roundabouts in Ireland with existing approaches with hard shoulders would cost very little (a few signs and realignment of road markings) and would eliminate a lot of what you term platooning which is proven to be a cause of major frustration leading to road casualties and fatalities.

You could even extend the idea to putting roundabouts on junctions with major Regional or Secondary roads which then both removes the danger of cars/ trucks parked in the middle of the road waiting to turn right and for folks travelling longer distances gives the opportunity to overtake slower traffic on the mainline exit

it's a good idea but we don't actually have many roundabouts. Take the poor-relation N20...2 roundabouts both in Mallow 50km/h limit

munchkin_utd

corktina wrote: »

it's a good idea but we don't actually have many roundabouts. Take the poor-relation N20...2 roundabouts both in Mallow 50km/h limit

it's true, but in practice they are fairly frequent on new stretches.

Heres a place for instance on the Tullamore by-pass where you could introduce a short overtaking lane exiting from a roundabout and make use of an otherwise complete waste of a hardshoulder.
http://goo.gl/maps/gp4QN

Its a route used frequently by trucks who by their nature are slow in accelerating and thanks to plentiful oncoming traffic you can normally give up on overtaking them so that 100kmh sign isnt even a target, its a forlorn dream.

JupiterKid

munchkin_utd wrote: »

it's true, but in practice they are fairly frequent on new stretches.

Heres a place for instance on the Tullamore by-pass where you could introduce a short overtaking lane exiting from a roundabout and make use of an otherwise complete waste of a hardshoulder.
http://goo.gl/maps/gp4QN

Its a route used frequently by trucks who by their nature are slow in accelerating and thanks to plentiful oncoming traffic you can normally give up on overtaking them so that 100kmh sign isnt even a target, its a forlorn dream.

I don't understand why the Tullamore bypass wasn't built as a 2+2.

So others do see merit in the idea of short sections of D2 for overtaking. I just think they would help on sections of National primary and strategic National secondary where there won't be major improvements/realignments anytime soon.

Sponge Bob

antoobrien wrote: »

It'd be unworkable unless there were at least two 2-3km stretches every 10km.

I suggested 10km of 2+2 and 20km of S2 interspersed continually on a lot of the routes that need something done..eg N5 N21 N24 .

Offline and ACCESS RESTRICTED, IF NOT Offline then S1, however S1 is a pointless road type IMO.

ardmacha

Offline and ACCESS RESTRICTED, IF NOT Offline then S1, however S1 is a pointless road type IMO.

S1 wouldn't be ideal, two cars going different ways would meet and you'd have stalemate.

But perhaps you mean something else? D1 S2?

Sponge Bob

ardmacha wrote: »

But perhaps you mean something else? D1 S2?

You mean S4 ( an undivided road type like the bridge approach in Galway) Nahhhhh.

niloc1951

THIS DOCUMENT make very interesting reading.
In it can be seen how the French have achieved a solution applicable to many of our wide S2 N and R roads for approximately €600,000 per kilometer, that's about 1/13th. the cost of a motorway build here.
The crash reduction statistics and lives saved and serious injuries avoided are very impressive for such a relatively modest cost.
And not a cheese wire in sight

Google Street View

Sponge Bob

Your streetview shows 2+1. We dont 'new build' 2+1 any more ( it could be retrofitted to existing roads in some cases) and the French have used 2+1 since the 1960s. We built a bit of new 2+1 on the N2.

That document is really about upgrading an EXISTING 2+1 to new shiny 2+1 where we are upgrading crap S2 roads in the main. It really proves we could upgrade GOOD WS2 to 2+2 for about the same cost, eg the Charlestown Bypass in Mayo.

Furthermore it says ...Page 3

An ambiguous and heterogeneous cross-section:
- alternation of 3 lane, 2 lane and 2x2 lane sections, all coupled with a posted 90 km/h speed limit,
- 3.5 m-wide lanes, whether overtaking is permitted or not.
A poor night time perception of the bends, with different radii of

The Swedes used 2+1 and found 2+2 ( same width no hard shoulder) better if building anew and so they stopped. We follow Sweden...a lot.

Many roads only need Type 2 S2 and then some 2+2 stretches at predictable intervals when bypassing some towns....certainly after 20km of S2 and for 10km length....thats my opinion anyway. EG the N5 or N21 or N53 or N15 would be a good example.

Our short 2+2 sections have a good safety record, we only have 3 on the N21 N3 and N4. They are overkill for roads often carrying 5-7k AADT save as overtaking sections. So is 2+1

L1011

The N3 2+2 section isn't particularly short.

niloc1951

Sponge Bob wrote: »

Your streetview shows 2+1. We dont 'new build' 2+1 any more ( it could be retrofitted to existing roads in some cases) and the French have used 2+1 since the 1960s. We built a bit of new 2+1 on the N2.

That document is really about upgrading an EXISTING 2+1 to new shiny 2+1 where we are upgrading crap S2 roads in the main. It really proves we could upgrade GOOD WS2 to 2+2 for about the same cost, eg the Charlestown Bypass in Mayo.

Furthermore it says ...Page 3



The Swedes used 2+1 and found 2+2 ( same width no hard shoulder) better if building anew and so they stopped. We follow Sweden...a lot.

Many roads only need Type 2 S2 and then some 2+2 stretches at predictable intervals when bypassing some towns....certainly after 20km of S2 and for 10km length....thats my opinion anyway. EG the N5 or N21 or N53 or N15 would be a good example.

Our short 2+2 sections have a good safety record, we only have 3 on the N21 N3 and N4. They are overkill for roads often carrying 5-7k AADT save as overtaking sections. So is 2+1

The Street View is of the section covered in the article.

There is a lot of 2+1 on the French D and N road network without physical barriers just very loud rumble strips and big penalties if caught on the wrong side

Reading the document seems to indicate that the pre-existing ,non-barriered, 2+1 like we have here except without the cheese wire, was upgraded to include jersey wall. THIS VIEW shows better that it was not a new build, but an existing S2 or 2+1 judging from the mature hedgerows.

Having driven on both jersey wall and cheese wire separated carriageways I much prefer the jersey wall. At night with jersey wall you don't get the strobe effect from the headlights of oncoming traffic, it gives the impression of being more robust, unless hit very hard at an acute angle, it needs no repairs (no ongoing maintenance cost) and it will not slice and dice anything which hits it.

Looking at the total carriageway width ditch to ditch, in the Street View bit, we have lots of wide S2 road here which could accommodate the same design and make travel so much less stressful and safer at minimal cost.

Having driven an average of 10k kms per year on non-motorway inter urban roads in Europe, mainly France, over the last seven years the only place I have seen the cheese wire is here at home, I haven't been to Sweden yet though.

flazio

Sadly Irish drivers aren't good enough to make this work, I can see many a rep mobile tearing the power as the road is coming back to one lane nudging the slow driver and blocking the whole show.