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Old September 20th, 2014, 09:52 PM   #341
sponge_bob
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Quote:
Originally Posted by Kanadzie View Post
Should never have lanes narrower than 3,75 m and constrained shoulder unless there is a real reason (existing viaducts or dense urban area...)
Wrong. Sweden has built an extensive network with 3.5+3.5m each side and others have copied that Swedish standard. It is a very safe kind of road at 100kph and is 16m across including the central median.

The reason we have hard shoulders is because cars up the the 1980s were very unreliable and needed somewhere to break down, and they did a lot. Legacy road designs up to the 1990s took this into account.

In a developed country like Estonia people have much more reliable cars nowadays and get them tested every year or two for roadworthiness and this means that there is no need for a space where they can break down any more.

Ireland even has motorways with 3.5m wide lanes and with speed limits of 120kph, they are perfectly safe roads. 3.75m wide lanes in Europe is gold plating save on very busy 4 lane or 4 lane + roads with traffic north of 30k AADT guaranteed.
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Old September 20th, 2014, 10:11 PM   #342
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It's not always clear if lane widths are between the road markings, or including the road markings. I agree that 3.5 m on motorways with a 120-130 km/h speed limit is fine.

However, a shoulder is not only for breakdowns, but also as a safety zone in case vehicles deviate from their lane. You don't want to get into a soft shoulder or into the median barrier once you cross the outer lines. This is why countries implement narrow shoulders, even on two-lane roads. The width of this shoulder varies by country, a left shoulder could be anything from 0.3 - 0.75 - 1.50 m.

Some countries specify a full width left shoulder if there are 4 or more through lanes in one direction, although it's usually the first design standard to be dropped for cost reasons.
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Old September 20th, 2014, 10:34 PM   #343
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To be honest Chris 2+2 with no hard shoulder also requires very good sight lines so that you can see a problem in 'your' lane a long way away, and speeds over 100kph with no hard shoulder are most unwise.

But it beats the crap out of every other rural long distance road design and is futureproofing for driverless cars which are not really all that far away now. Motorway is overkill at under 15k AADT within a few years of construction and a lot of countries have spent a huge amount of money on Motorways where a 2+2 would often do.




Therefore, and with all we have learnt about safety and with the prodigous drops in road fatalities in countries that have converted their long distance networks to 2+2 in recent years I think that all trunk networks should be designed as an access controlled 2+2 of some sort. If that can be done with a 16m pavement ( where quite a few countries countries were building many 1+1 roads with shoulders in 13m for many years) that is a good long term investment to my mind.
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Old June 13th, 2015, 03:01 PM   #344
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A9, the main north-south route to/in Scotland, has a few 2+1 sections. I took these recently:





There are a lot more 2+2 sections with proper center reservation though.
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Old July 24th, 2015, 01:08 AM   #345
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SP-333 in São Paulo state




BR 487 in Parana State In Brazil


BR 487 (PR) by Programa de Aceleração do Crescimento, no Flickr



SP-300 in São Paulo state


SP-300 Marechal Rondon by a_fourier, no Flickr

SP-267 in São Paulo state


SP-264 Francisco José Ayub by a_fourier, no Flickr
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Old July 25th, 2015, 04:24 AM   #346
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Another example here in brazil


Inauguração de obras da SP-351 e investimentos em turismo em Nopuranga e Batatais by Governo do Estado de São Paulo, no Flickr
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Old August 13th, 2016, 02:22 PM   #347
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One from Macedonia, on the recently opened reconstructed section of the road Bitola-Resen



(pelanet.mk)
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Old August 14th, 2016, 12:08 PM   #348
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Found these two photos of E4/E10 in Norrbotten, Sweden.


E4 in northern Sweden by Timon91, on Flickr


E4 in northern Sweden by Timon91, on Flickr
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Old August 16th, 2016, 10:11 PM   #349
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Quote:
Originally Posted by metasmurf View Post
Found these two photos of E4/E10 in Norrbotten, Sweden.


E4 in northern Sweden by Timon91, on Flickr


E4 in northern Sweden by Timon91, on Flickr
These figures make it easy to understand why the Swedish 2+1 implementation faces criticism. The one-lane part is very narrow and therefore in danger to be blocked on a vehicle failure or by a tractor.

Many of the new 2+1 roads in Finland are equipped with a lightweight parallel road for local traffic and agriculture vehicles. There may also be a parallel road on the both sides of the main road, and connecting underpasses.





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Old August 18th, 2016, 01:54 PM   #350
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Quote:
Originally Posted by MattiG View Post
These figures make it easy to understand why the Swedish 2+1 implementation faces criticism. The one-lane part is very narrow and therefore in danger to be blocked on a vehicle failure or by a tractor.

Many of the new 2+1 roads in Finland are equipped with a lightweight parallel road for local traffic and agriculture vehicles. There may also be a parallel road on the both sides of the main road, and connecting underpasses.
The road in the picture was already a 13m wide 2-lane road. If all 13m roads would have had to be widened to 14m the 2+1 road network would be less extensive than it currently is due to higher costs.

For new stretches in new alignments or widening from 9m (or less) the 14m profile is used.

As for parallel roads. I don't know the exact spot where the picture I posted was taken, but generally parallel roads are constructed in all 2+1 conversion projects if there aren't any alternative roads already in place. Thus alternative roads may not be directly alongside the 2+1 road, but there's always an alternative in case the road gets blocked.

Yes it would be better to have 14m wide roads and parallel roads directly alongside the road, but road budgets are finite, and priorities have to be made.
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Old August 19th, 2016, 03:18 PM   #351
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Originally Posted by metasmurf View Post
The road in the picture was already a 13m wide 2-lane road. If all 13m roads would have had to be widened to 14m the 2+1 road network would be less extensive than it currently is due to higher costs.
I believe people in this forum are rather well aware of the facts behind the narrow 2+1 roads in Sweden. In my opinion, they are much better than the previous wide-shoulder 1+1 roads. The driving on those was somewhat non-disciplined (and stressing) because there was no common code on how to drive on those.

There is one oddity on the Swedish 2+1 roads, which is visible in this picture:



At many (all?) grade-separated junctions, the entry lane continues as the right lane, and the thru-traffic flows on the left lane. Thus, the thru-traffic must change the lane after every junction, because the left lane is the ending one. This violates the best practice to allow the thru-traffic to keep its lane, and to add extra lanes at left.
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Old August 19th, 2016, 04:01 PM   #352
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Basically that's a design one can also find in Germany.
E.g. on the B 1 from Paderborn towards Hameln https://www.google.de/maps/@51.78018.../data=!3m1!1e3
or on the S 177 near Pirna https://www.google.de/maps/@50.99955.../data=!3m1!1e3


(from 1:50 onwards)
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Old August 19th, 2016, 04:52 PM   #353
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In Brazil


SP-270 Raposo Tavares by a_fourier, no Flickr


SP-304 Dep. Leonidas Pacheco Ferreira by a_fourier, no Flickr


SP-255 João Mellão by a_fourier, no Flickr


SP-255 João Mellão by a_fourier, no Flickr


SP-225 Ciro Albuquerque by a_fourier, no Flickr
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Old August 19th, 2016, 04:56 PM   #354
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Are 2+1 roads as common in other parts of Brazil as they are in the state of São Paulo?
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Old August 19th, 2016, 05:11 PM   #355
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Are 2+1 roads as common in other parts of Brazil as they are in the state of São Paulo?
Yes, but just on Federal roads i.e. BR's

BR 265 in Minas Gerais state



BR-116 Santa Catarina state



BR-222 Ceara state




BR 487 Parana state


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Old August 20th, 2016, 09:18 PM   #356
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Quote:
Originally Posted by MattiG View Post
At many (all?) grade-separated junctions, the entry lane continues as the right lane, and the thru-traffic flows on the left lane. Thus, the thru-traffic must change the lane after every junction, because the left lane is the ending one. This violates the best practice to allow the thru-traffic to keep its lane, and to add extra lanes at left.
I can't speak for the rest of Sweden but around here it generally works well, though I've seen some foreign drivers not understanding the concept. Maybe this concept is more problematic further south in Sweden where the traffic volumes are generally higher.

With that being said, I agree that it's not optimal for the reasons you stated, but I guess the reason is (once again) money to avoid widening bridges for under-passing roads or bikepaths. Here's an example:


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Old August 21st, 2016, 01:06 PM   #357
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Quote:
Originally Posted by metasmurf View Post
I can't speak for the rest of Sweden but around here it generally works well, though I've seen some foreign drivers not understanding the concept.
Well... Basically, if some road concept is hard to understand by non-locals, there is something rotten in it.

Quote:
With that being said, I agree that it's not optimal for the reasons you stated, but I guess the reason is (once again) money to avoid widening bridges for under-passing roads or bikepaths.
Somewhat difficult to believe, as the position of the needed extra width does not lie at the bridge (with the exception of a type-A parclo junction). Let us see a following chart. Compared to the upper setup, the lower one provides the thru-traffic with a continuous flow. The lower one does not need extra space at the bridge.



If the extra width at the end of the entry ramp is a problem, the 2-lane section can be started slightly later, like in this chart:



Thus, I believe that there is other reasons behind this design.
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Old August 21st, 2016, 01:17 PM   #358
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B54 in Germany (Gronau - Münster) is one of the longer 2+1 roads in the country (50 km) and uses this concept where the entry lane becomes the right lane, so through traffic indeed has to change lanes at every interchange. I usually drive this road a few times per year, and it doesn't appear to be a problem.

B54 suffers from relatively high volumes of truck traffic. Especially on work days there is a continuous flow of trucks, so each time it narrows from 2 to 1 lane you'll get stuck behind a slow-moving truck. You can't really drive the speed limit for very long.
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Old August 21st, 2016, 02:40 PM   #359
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As a driver, I'd strongly prefer the top example, since it totally avoids the bottleneck of the onramp merging into a single lane. Everyone gets its own lane and all the merging manouevers can be carried out easily on a longer distance.
I know a couple of places where the second design is applied, and they're very confusing. When merging, you'll never know if oncoming drivers will keep their left to let you in, or stick to the right lane (wasting capacity).

An example: https://www.google.it/maps/@44.52855...7i13312!8i6656

Here you can see that the merge only works because the trucker is sticking to the left to let the other merge... virtually applying the design were're talking about.
To me it's pretty obvious: two lanes come in, two lanes get out, each one continues straight. No bottlenecks.


The point here is how distant is the 2-to-1 narrowing.
If it's close to the junction, I agree it's annoying for drivers on the main lane because they're all forced to switch lane in a relatively short space (it becomes a sort of "inverted onramp").
If it's far at least some 2-3 km from the junction, or more, then I see no big deal with this design. It's just an extra lane added to the right, and requires just a lane change like the thousands a driver must do on a 2+ lanes road.
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Old August 22nd, 2016, 07:03 AM   #360
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SP 345 in Brazil



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