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Discussion Starter · #1 · (Edited)

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leptokurtic
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In the Netherlands guard-rails are definitively more prevalent. Newer high-performance guard-rails have as much containment capacity as hard concrete barriers and they are deformable.
 

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I always though that concrete barriers were stronger and thus safer, especially in case of impact with a truck, but maybe also modern steel ones are as safe.
 

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Concrete barriers, especially if you have two filled with sand, make sure vehicles cannot cross the median. However, they are also not forgiving, you have a much better change of getting away unharmed if you drive into a metal crash barrier than if you drive into a solid wall.
 

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If you make metal barriers and you want to avoid vehicles landing on the other side, do what the Italians do. No-nonsense barriers. Obviously the planners know what their drivers are like...

 

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Deadpan Snarker
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It would slow you down, though....
 

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Discussion Starter · #10 ·
In Singapore, most are guard rails other than the the newest expressway, MCE, it's a continuous Jersey barrier.
In Malaysia ,most of the older expressway are using guardrails ,only when there's a viaduct crossing it does it use a solid Jersey barrier. The newer expressways are mostly consist of jersey barriers in the median with guardrails in isolated areas (hardly full length of the highway)
 

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You'll come to a full stop on the other side. This is true. So will oncoming vehicles.
Realistically no, there is a big depression, you tend to crash into the soft dirt

If the median is too narrow though crossover is possible, there were a couple of high-profile accidents in Ontario on Hwy 401, the early built sections (1950's) where traffic crossed narrow grass strip median and had a big crash. But once you have 30 metres of median it is okay.
 

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If you got a heavy goods vehicle travelling at 60 MPH on cruise-control, and the driver is flagging and eventually falling asleep, don't you think it will create a dangerous situation to oncoming traffic on the other side of the highway as well?
 

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Honestly I can't remember any real issue like that occurring and this type median is very common in the USA and Canada. Typical crashes with HGV's are jacknifing, even flipping over, but not crossing the median (mind you, the slope is great enough to flip the typical HGV over, that might be the real issue)

There's a big question, in that having a hard barrier necessarily is dangerous to errant vehicles, while something like a depressed median is very safe to errant vehicles, but has a theroretical (becoming significant to extreme as the width narrows) crossover possibility. But if you have a very wide one, it's very safe.
 

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insertoronto
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That isn't the standard rural highway width, that area is skinnier than normal so that it can be eventually expanded to a 10 lane cross section.

A modern rural separation is this, notice the large depression which is a primary function in stopping vehicles.

https://www.google.ca/maps/@45.4296...ata=!3m4!1e1!3m2!1sjWmxx0yE-xYgVluMZv2puQ!2e0

The "Ontario Tall Wall" is a concrete median invented by the MTO that has been exported across the world. its basically a taller version of the standard barrier more commonly seen. Here you can see the Tall Wall on the left and the regular type barrier on the right.

https://www.google.ca/maps/@43.3882...ata=!3m4!1e1!3m2!1sV92TQ4Hz9GQi1oc9wtvTAg!2e0

The most substandard portion of Ontario highways is this kind of barrier, which is honestly rather scary. This used to be the standard median, but only 2 sections remain and both of which will be replaced in the next few years:

https://www.google.ca/maps/@44.10422,-79.631875,3a,75y,197.42h,84.78t/data=!3m4!1e1!3m2!1s-o5SeLSIBgosiXqcwEK4zQ!2e0
 

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30+ meters wide grassy medians are suitable only where there is a lot of empty land available, like in North America but not in most of Europe, where sprawl is common in the countryside.
The only divided highway with wide grassy median I've seen in Europe (from internet, never been there), is the expressway around Reykyavik.

In Italy A22 between Modena and Verona has a grassy median (far narrower than 30m, though), to accomodate a future 3x2 widening. Of course, it has steel crashbarriers in between.
https://www.google.it/maps/place/46...2!3m1!1s0x4781d40f82e52ed9:0xc1c7fd07590e7b85
 

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The Road and Map Geek
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30+ meters wide grassy medians are suitable only where there is a lot of empty land available, like in North America but not in most of Europe, where sprawl is common in the countryside.
The only divided highway with wide grassy median I've seen in Europe (from internet, never been there), is the expressway around Reykyavik.
A few samples about the standards in place in Finland:


4/E75 Järvenpää


3/E12 Hyvinkää


7/E18 Porvoo

The minimum width of the median is 15 meters if the road is designed for 120 kph speed.

Another type, a narrow motorway, design speed 100 kph:


8/E18 Liminka
 

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In Italy, is more prevalent the "double waved" guard-rail, widespread on almost all italian motorway net
In some case were used the concrete new jersey.

Recently the public opinion was worried by new jersey because, specially on the Southern part of the contry, because some new jersey wasn't fixed on the ground!!! (too much work for the Southern, or save some money?)

From Wikipedia: Motorway A16...
On the night of 28 July 2013, a serious traffic accident occurred on the A16 near Avellino when a coach carrying pilgrims fell off a flyover into a ravine. At least 39 people, including the driver, were killed and many others injured.
However, the italian Highway Code prescribes a reservation of 3,20 meters (3.2m = 10ft 5in), but didn't specify how divide the opponent traffic.

There was a public debate in the late of 60s about this question, there was to choose between a large reservation (12 meters [39ft 4in], with only advisory barriers) versus a narrow reservation (from 1 [3ft 3in] to max 3 or 4 meters [9ft 10in or 13ft 1in]) that must have barriers.
In Italy, you can guess who have won...

I'd prefer the solution saw on A22 between Modena and Verona (as seen in a recent post above) but, Italy doens't have a lot of plain to have that characteristics for the dual carriageways
 

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Italy doens't have a lot of plain to have that characteristics for the dual carriageways
Motorways in mountanious areas are safer from this point of view because parallel tunnels and viaducts (of opposite directions) are usually detached each other and it's impossible to run into the opposite carriaggeway.

One example of very dangerous median:
https://www.google.it/maps/place/Si...2!3m1!1s0x1313ce8da28bdf79:0xd1736683b2c58b87
Highway Augusta - Siracusa, Sicily
Intended to be part of the A18 but currently numbered SS114 as it has too low standards for a motorway, although it's fully integrated with the rest of the motorway network.
 
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