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Old June 23rd, 2016, 11:55 PM   #1021
bgdimitrov
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Since the render image of the roundabout seems to have sparked a lot of discussion, I will post another image (daytime) of how it actually turned out. The roundabout is relatively busy, especially at rush hour. The majority of the public transport of the city passes through the roundabout as well. What is now much better than before is that there is no longer the need for drivers to look out for pedestrians. Prior to this it was common for jams to occur due to pedestrians crossing and vehicles having to wait inside the roundabout.

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Old October 26th, 2016, 02:55 AM   #1022
Wilhem275
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Show me your aprons!

In recent years many Italian cities built a sh!tload of roundabouts, especially in urban areas, mostly to replace traffic lights (which IMHO were often just poorly timed, but that's another story).

As everybody knows, inside Italian cities space is often a problem, so many of these new roundabouts were designed with a very small diameter. Now, the problem that comes with small diameters is that the tail of long vehicles will need a lot of extra space to cut the curve.
What comes with this, is that the apron (the part of inner ring for truck manoeuvres) is unusually wide compared to the proper drivable area.
But this would not be a big deal, if properly realized.

The problem is that Italian cities always had the bad habit of not actually drawing intersections: just dump a field of tarmac, put a stop sign somewhere, and job done. Cities don't have the culture of designing precise guidance thorugh intersections.
The same applies to roundabouts: there is no distinction between the apron and the actual lane, just a load of tarmac.
The obvious result, in a place where the average driver is constantly looking for the tightest apex, is that cars will drive using a much smaller circle, and drivers proceeding straight will often just cut through it.

This is an example of how a properly designed apron completely disappeared in the real building:



As you can see, a 24 m roundabout is then used as a mere 16 m one, while all the surrounding elements were designed for a different setup. A car can clearly cut all corners and floor it through the whole thing.

Almost all Italian roundabouts show the same issue. And when the apron is present, it's often vastly undersized or marked so poorly that all cars will drive at speed over it.

I want to propose changes to this situation. And since my fellow drivers will drive over their own mothers if there isn't a tall wall surrounding them*, aprons need to be as much as undrivable as they can be.

So, please show me your examples of the most violent, badass, cars-destroying aprons you know of
I want to see how tall and aggressive these structures can be before ruining or rolling over trucks and buses



*seriously: you can mark and draw and signal the hell you want, but if they can physically put wheels over something, they will drive through it. You must guide them like trains.
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Old October 26th, 2016, 02:57 AM   #1023
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is it problem though?
I mean, is there dead people? :P
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Old October 26th, 2016, 08:25 PM   #1024
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Deadly accidents are rare on roundabouts, due to generally low speeds. However, larger roundabouts are generally safer than smaller ones, that's why they try to make them big where there's enough room.
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Old October 26th, 2016, 09:14 PM   #1025
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Your sentence contradicts itself. If low speeds are the key to safety then smaller roundabouts should be safer than bigger ones...
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Old October 26th, 2016, 09:16 PM   #1026
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No, because if they're really small they're basically a dot in the middle of the intersection you don't have to slow down for, if they're bigger you have to make a turn so you have to slow down.
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Old October 26th, 2016, 11:05 PM   #1027
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Quote:
Originally Posted by Rebasepoiss View Post
Your sentence contradicts itself. If low speeds are the key to safety then smaller roundabouts should be safer than bigger ones...
It should be clarified as "actually larger roundabouts" are safer. A wide but narrow ring means sharp corners with the feeding roads, forcing to slow down.
If the roundabout is wide but drivable in the middle like a small one, it carries the defects of the small one (no real obstacle when going straight) and of wide lanes (poor feeling of speed).

Here some good examples:


Most Dutch roundabouts have a large diameter, but traffic is not allowed to cut through the ring, so they work safely.
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I've sold monorails to Brockway, Ogdenville, and North Haverbrooke, and by gum, it put them on the map!
Well, sir, there's nothing on earth like a genuine, bona fide, electrified, six-car monorail!

Marchionne means never having to say you're sorry.

Due to Photobucket f*cking up, most images won't be visibile in my old posts. If you need anything specific, please write me.

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Old October 26th, 2016, 11:12 PM   #1028
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Many Dutch roundabouts have the same dimensions on a 30 or 50 km/h urban street as on an 80 km/h provincial road. In my opinion they should allow a higher design speed (more driving comfort) on rural roundabouts with no bicycle paths present.

Some provincial roads are riddled with roundabouts and semi trucks in particular often need up to a kilometer to regain speed. Gelderland province in particular has way too many roundabouts on provincial roads in areas with no motorways or other high-speed roads.
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Old October 28th, 2016, 01:45 PM   #1029
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Quote:
Originally Posted by Wilhem275 View Post
It should be clarified as "actually larger roundabouts" are safer. A wide but narrow ring means sharp corners with the feeding roads, forcing to slow down.
If the roundabout is wide but drivable in the middle like a small one, it carries the defects of the small one (no real obstacle when going straight) and of wide lanes (poor feeling of speed).

Most Dutch roundabouts have a large diameter, but traffic is not allowed to cut through the ring, so they work safely.
OK, I see what you mean

That being said, you can make a small roundabout that forces drivers to slow down as well. One example. In this case you can drive over the middle but you really don't want to. The exit speed is theoretically lower than entry speed (ideally it should be the other way round) but the roundabout is so small that you have to brake before entering it anyway.

Edit: spelling.
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Last edited by Rebasepoiss; October 28th, 2016 at 06:20 PM.
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Old October 28th, 2016, 02:05 PM   #1030
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Quote:
Originally Posted by Rebasepoiss View Post
OK, I see what you mean

That being said, you can make a small roundabout that forces drivers to slow down as well. One example. In this case you can drive over the middle but you really don't want to. In this case the exit speed is theoretically lower than entry speed (ideally it should be the other way round) but the roundabout is so small that you have to break before entering it anyway.
I can assure you that, in Italy, that roundabout would be treated by the vast majority of drivers as "non-existent".
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Old October 28th, 2016, 03:05 PM   #1031
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Most people drive around, but I just drive over this.
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Old October 28th, 2016, 05:23 PM   #1032
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Quote:
Originally Posted by Rebasepoiss View Post
That being said, you can make a small roundabout that forces drivers to slow down as well. One example. In this case you can drive over the middle but you really don't want to.
Yep, that is the concept, but as Spinoza said: an apron that high is not not even perceived by Italian drivers.
I'm still looking for something much, much more badass something that under 15 km/h gives high discomfort, and over 15 will easily ruin a car.

Basically, I need the equivalent of a car trap:



image hosted on flickr


The tricky part is that it must work on a tight curve. All these work well because the bus will reach them straight and you are sure of the wheels position; in a roundabout there's no sure position.
The matter is to find the taller obstacle that can be overridden sideways by bus and trucks tyres with no damage (at very low speed, which they will have anyway).
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I've sold monorails to Brockway, Ogdenville, and North Haverbrooke, and by gum, it put them on the map!
Well, sir, there's nothing on earth like a genuine, bona fide, electrified, six-car monorail!

Marchionne means never having to say you're sorry.

Due to Photobucket f*cking up, most images won't be visibile in my old posts. If you need anything specific, please write me.

Last edited by Wilhem275; October 28th, 2016 at 05:40 PM.
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Old October 28th, 2016, 06:28 PM   #1033
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Quote:
Originally Posted by Wilhem275 View Post
I'm still looking for something much, much more badass something that under 15 km/h gives high discomfort, and over 15 will easily ruin a car.
Umm, I'm not sure what you're looking for. If you drive over flowers in my example, your car won't like it.
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Old October 28th, 2016, 06:30 PM   #1034
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Yup, something like that would be a better solution for countries where traffic laws aren't followed that strictly. In Estonia, however, one of the things all road engineers have to think about is: how do you plow snow here? Car traps like shown above (1, 3, 4) wouldn't work at all for that reason.
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Old October 28th, 2016, 07:04 PM   #1035
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Yup, I can only imagine dealing with such a quantity of snow...

The traces here tell us that many just drive straight through that thing

Quote:
Originally Posted by Verso View Post
Umm, I'm not sure what you're looking for. If you drive over flowers in my example, your car won't like it.
Flowers won't like it either the problem is that a truck would be damaged as well.
What I need is a compromise.

It's also a visual issue. Take the first example i posted: in a small roundabout, a proper apron is way bigger than the car lane itself. Not only the apron should have an aggressive ring, it should also be filled with a non-regular surface (something that says "Hey, I'm not meant for driving").
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I've sold monorails to Brockway, Ogdenville, and North Haverbrooke, and by gum, it put them on the map!
Well, sir, there's nothing on earth like a genuine, bona fide, electrified, six-car monorail!

Marchionne means never having to say you're sorry.

Due to Photobucket f*cking up, most images won't be visibile in my old posts. If you need anything specific, please write me.
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Old October 28th, 2016, 10:40 PM   #1036
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This one.
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Old October 29th, 2016, 12:14 AM   #1037
Wilhem275
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Now we're serious
At the moment, it's the main solution I had in mind. The angle of those curbs seems to be the best compromise.
I'd even try a second layer of that, let's say 1 m smaller than the first ring (to scream "Really, don't think about it!").

Yet again, this last example is another case in which the paved area is WAY bigger than what is needed, even for trucks.
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I've sold monorails to Brockway, Ogdenville, and North Haverbrooke, and by gum, it put them on the map!
Well, sir, there's nothing on earth like a genuine, bona fide, electrified, six-car monorail!

Marchionne means never having to say you're sorry.

Due to Photobucket f*cking up, most images won't be visibile in my old posts. If you need anything specific, please write me.
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Old October 29th, 2016, 10:35 PM   #1038
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http://static.primorske.si/foto/lowr...0-krozisce.jpg

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Old June 4th, 2017, 08:46 PM   #1039
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Roundabout Safety:
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Old December 31st, 2017, 05:18 PM   #1040
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Roundabout - Austria - Waidhofen an der Thaya ("Waldrapp"):







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