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As far as I know, pretty much all the studies (except those coming from the Netherlands) show a decrease in car accidents (or an increase in accidents but decrease in severity), but an increase in cyclist and pedestrian injuries. The reason the ones in the Netherlands work is because they design them with dedicated lanes for pedestrians and cyclists outside of the circle, with the peds and cyclists having priority. eg: https://www.youtube.com/watch?v=wEXD0guLQY0 Also, that kind of retrofitted, "just add a round traffic island to a four-way intersection" style of traffic circle in question in Corvallis is very common in Vancouver. In fact, they got built as "traffic calming" measures along bike routes, but a recent study showed that they were the most dangerous type of intersection to cyclists by a very wide margin, topping even uncontrolled intersections. http://injuryprevention.bmj.com/content/early/2013/02/13/injuryprev-2012-040561.full They recently removed one at 10th and Pine because it was one of the highest cyclist-accident locations in the city: http://goo.gl/maps/s9w17 I mean, traffic circles, when designed well, can improve traffic flow and reduce injuries. But if you don't have the space and/or political will to do them right, they can be a major obstacle to liveability in your city/town.
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Aug 2, 2013 21:17
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Holy gently caress they built a ton of these in a neighbourhood near mine and back when I rode a bike everywhere the only times I've nearly been hit were in these stupid mini traffic circle things. Except of course they weren't actually circles, they were just big obstacles put in the middle of what was a 4-way stop or uncontrolled stop. Also some of them still had stop signs while others would have yield signs or a mix so it was gently caress-off inconsistant and everyone hates them, except the immediate residents loved them because it made their roads unsafe and annoying so people took different routes. Some people would just drive straight through if they were small and nimble enough, doing a dangerous little zig-zag to get around the planter or what ever was in the middle. Other people would treat it as a 4-way stop. And other people would treat it like a proper round-about. And of course people turning left had about a 50% chance to just turn left instead of driving around it counter-clockwise like a proper traffic circle. Many were also designed so that a bike could zip through the middle. A total poo poo-show. Baronjutter fucked around with this message at 21:32 on Aug 2, 2013 |
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Aug 2, 2013 21:27
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I think it would be much better if there were more of them in the US and they were done more consistently.
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Aug 2, 2013 21:48
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Lead out in cuffs posted:As far as I know, pretty much all the studies (except those coming from the Netherlands) show a decrease in car accidents (or an increase in accidents but decrease in severity), but an increase in cyclist and pedestrian injuries. The reason the ones in the Netherlands work is because they design them with dedicated lanes for pedestrians and cyclists outside of the circle, with the peds and cyclists having priority. Well... that's mostly true. There's also roundabouts like that where cars have priority over peds and cyclists. Usually that's made clear with signs and 'shark teeth' (yield marks on the ground). There's some conflicting information about that on the internet. It seems that the car priority ones occur more often outside towns, but cyclist priority becomes more and more common. Some sites state that a close reading of the law suggests that even if cars have priority, that's only true when entering the roundabout. When leaving it, cyclists staying on the roundabout always have priority. That's a very confusing situation, which is usually prevented with signage. I also found that some study showed that dedicated lanes with cyclist priority is theoretically less safe than dedicated lanes with car priority. However, cyclists going straight ahead always have priority over turning cars in regular intersections, so car priority would break uniformity. Additionally, regardless of priority, cyclists don't like to stop, especially if they have to go the long way 'round already. So in practice, there isn't really a difference in safety between those two options. An older theoretical study confirms that it doesn't matter much. Carbon dioxide fucked around with this message at 23:43 on Aug 2, 2013 |
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Aug 2, 2013 23:40
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There are plenty of studies on roundabout safety, and most of them show a ~70% reduction in serious accidents and a near-elimination of fatal accidents. The overall accident reduction is a bit lower, probably near 30%, and depends on what kind of intersection you had before. It's absolutely indisputable that roundabouts reduce vehicle accident frequency and severity. Their safety record continues to improve as we work on refining our designs. For pedestrians, the difference isn't as striking, but research does show a reduction in ped accidents. Drivers are going more slowly, and are more likely to yield to peds. Additionally, each leg has a refuge island. The only ped group severely disadvantaged by roundabouts are the blind, since they have a hard time hearing where cars are coming from and where they're going. Before long, we'll be putting ped signals on a lot of our roundabouts, so that should help. Now for bicyclists, I've seen mixed messages. Bike accidents are so low in the studies I've seen, both before and after, that there's a statistically insignificant change in the accident rate. A big reason for those accidents that do occur is bicyclists not knowing how to ride through a roundabout. If they're comfortable with their abilities, they should act just like a car and stay about 2/3 of the way toward the outside of the circulating roadway. When you see someone ride like that, it seems effortless. If they're less comfortable, they need to dismount and go around the circle like a pedestrian, on the sidewalk. Many roundabout designs include a bike-specific ramp from the road to the sidewalk so they don't even have to dismount. Either way, when a bicyclist gets hit, the outcome is much better when the car is going 20mph vs. 30mph.
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Aug 3, 2013 02:12
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Roundabouts and traffic circles also have something of a bad reputation from the fact that many Eastern states had built tons of them back in the 30s-60s, and over time most of those have become overloaded with traffic to the point where they just couldn't cope. And now those either sit there continuing to be pains in the rear end or have been replaced by real grade separation, cut-throughs with traffic lights, or combinations of those in various ways. And that's to say nothing of how many recent ones were just "take existing intersection in town, remove traffic lights, jam some random object in the middle".
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Aug 3, 2013 02:18
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Well, you can really, really gently caress up a traffic circle too. Let's add weaving to the design! http://goo.gl/maps/fpbGB
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Aug 3, 2013 04:27
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The most famous horrible traffic circle in Europe I know is the Place Charles the Gaulle around the Arc de Triomphe in Paris. overhead view and streetview. Some weird photo artefact in the sky there. French UFO. Whatever. It's a twelve-way (?) intersection, the circle is wide enough for many cars, but there aren't any lanes and people just drive wherever. I heard that French insurance companies actually put a specific clause in their contracts that cars aren't insured while on that one traffic circle. I have no idea how many accidents per day happen there, but I do know that if you decide to drive there, you can expect to leave the place with a few new dents in your car. E: Did I mention that Parisians in practice seem to use the priority rule "whoever goes first, goes first" and you have to show the exact right level of boldness to get through to the right exit without causing a jam? Nobody really seems to know what that level is. It all boils down to survival of the 'fittest'. Carbon dioxide fucked around with this message at 06:39 on Aug 3, 2013 |
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Aug 3, 2013 06:28
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That roundabout shows that this thread is also going in circles.
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Aug 3, 2013 08:29
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Carbon dioxide posted:Some weird photo artefact in the sky there. French UFO. Whatever. Yeah, that's Google's automated photogrammetric processing right there. It tends to generate weird stuff like this all the time really.
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Aug 3, 2013 20:14
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Yes, it's like a lava lamp.
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Down in Houston the outlying suburbs have developed far beyond the capabilities of the local county municipality's capacity to think forward. Resignation of these commissioners and engineers is necessary, because it's just not working out and the community has suffered for it. One may call the number on the signal control box and nothing gets done, and if so, it's the wrong thing and done inefficiently. Pollution is building out here as developers build more residences in place of forest, and bad traffic management isn't helping. The signal systems are even left on overnight, using more energy than flashing mode and routinely stopping drivers who catch the tail end of the timer. Speed limits are routinely too low or high; low speed limits causing real traffic speed to be unpredictable to entering drivers. Construction companies are installing median divided boulevards without consideration to right turn traffic. These minimal-thickness slabs aren't lasting long here where many of the residents have large vehicles. And those right turn lanes removed when the widened the road: a safety, and noise and air pollution source as high frequency turning traffic conflicts with a main thoroughfare of drivers carrying on. Years ago I didn't get sinus infections when I lived in Houston. I moved away after becoming sick from routine outdoor activity. When I return, it's always the same and slightly more populated. How about those permissive left turns, I ask the dispatcher; "that idea is currently under study." Well, dear county employees, Pittsburgh lefts have been done before. Just do something creative and productive already, with our limited tax resources, or hang up your hat for someone mindful. Minds that think like yours would be welcome here, but be careful not to hang around in the carbon monoxide for too long.
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Aug 3, 2013 23:59
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As far as I can tell the South is basically hosed by bad urban design resulting from the mid-20th century car mania, and continues to be hosed by the modern political climate down there. I don't think any amount of traffic engineering is going to fix that, and blaming the engineers for trying to make the best of a bad situation is pretty mean.
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Aug 4, 2013 08:41
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Lead out in cuffs posted:As far as I can tell the South is basically hosed by bad urban design resulting from the mid-20th century car mania, and continues to be hosed by the modern political climate down there.   Some Flex routes have been embraced, others not so much. Over 10/hour is pretty good for a bus that can only hold 12. 
Varance fucked around with this message at 17:17 on Aug 4, 2013 |
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Aug 4, 2013 16:08
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Lead out in cuffs posted:As far as I can tell the South is basically hosed by bad urban design resulting from the mid-20th century car mania, and continues to be hosed by the modern political climate down there. South ain't, and will never be hosed. Development decisions have been made around there that don't line up long term. Operations have stagnated from indolence on a larger level by many of those involved in the municipalities. Pittsburgh lefts and night flashers. Good example right there that's been done and should have been years ago to help flow. I am under the impression that control equipment would not have to be replaced for those things to happen, but instead it's a matter of programming the units. These positions were created by the people to service an ongoing civic need. You only need to travel up to The Woodlands or two hours over to Austin to see what pretty good traffic management (even if now very congested) looks like.
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Aug 4, 2013 16:47
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grillster posted:South ain't, and will never be hosed. Development decisions have been made around there that don't line up long term. Operations have stagnated from indolence on a larger level by many of those involved in the municipalities. grillster posted:So the left turn light flashes yellow during a 2 second protected phase? Given that Tampa has a lot of Northeastern US transplants, people Pittsburgh left all the time around here to begin with. The only change is that the intersection gives them a heads up of when to do it. 
Varance fucked around with this message at 17:21 on Aug 4, 2013 |
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Aug 4, 2013 16:57
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So the left turn light flashes yellow during a 2 second protected phase?
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Aug 4, 2013 17:02
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 this is the 128/pike intersection a little east of boston, I think one of the worst intersections I've ever seen first off, you have the EZ-pass lanes on both sides of the regular tolls, which would work except that the road is suddenly squeezed down to much fewer lanes in a very small amount of space. This means that it's almost always jammed with tons of cars, and to make matters worse, there are always idiots who didn't plan ahead trying to cross over the sea of cars to come out the other side. Then you have this little area on the right clearly marked "Do not enter", which I've seen idiots drive up every single day after being fed up with the giant mess of a traffic jam (the route marked in red). I assume they encounter the oncoming traffic, then make a hairpin turn to merge onto the exit ramp, it's absolutely insane. And THEN you have this mess of weaving coming from the terrible ramps up ahead. (orange/pink) People are normally coming in pretty fast from i90 west, since the traffics considerably lighter going outbound during rush hour, so I'm always scared for my life entering here. The final ramp (dark red) is just plain confusion, it seems to alternate between people forming 2 lanes, 1 lane, and just making a mess of cars every few minutes. By the end of the ramp it's clearly only fit for one vehicle, but the majority of the ramp is definitely wide enough for 2, although it's not really marked as such. People will form a single lane, and then some crafty guy will decide to breeze by everyone, so more people follow him, but they have to merge right back into one lane in only about 100m, so it just causes a mess how on earth did anyone come up with this?
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Aug 5, 2013 16:32
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The fact that it was originally built before the turnpike extension (it just ended at route 128) and then later expanded probably has a lot to do with it.
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Aug 5, 2013 16:58
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Q: What takes two weeks to make and looks awesome? A: This! 
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Aug 8, 2013 21:46
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Cichlidae posted:Q: What takes two weeks to make and looks awesome? it's so... graphy and chartey 
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Aug 8, 2013 22:45
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Cichlidae posted:Q: What takes two weeks to make and looks awesome? Color code the ADT line by level of service!
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Aug 8, 2013 22:52
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Devor posted:Color code the ADT line by level of service! Pfft, I don't even want to have to mess with our pen tables. But I guess I could do it in Bluebeam, then set up different files for am and pm peaks. Maybe a whole video based on a typical week, with colors representing density... Edit: I guess it wouldn't even take as long as the VISSIM I'm doing: the entirety of I-95 from New York to New Haven, ramps, signals, everything, so we can do a value pricing study. Now there's a public servant's worst nightmare: spending billions on infrastructure that only the rich can use. Cichlidae fucked around with this message at 23:04 on Aug 8, 2013 |
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Aug 8, 2013 22:55
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Cichlidae posted:Pfft, I don't even want to have to mess with our pen tables. But I guess I could do it in Bluebeam, then set up different files for am and pm peaks. Maybe a whole video based on a typical week, with colors representing density... Feed it into a tone generator so you get a nice soothing hum during the low times and dubstep during rush hour.
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Aug 8, 2013 23:04
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Terminal Entropy posted:Feed it into a tone generator so you get a nice soothing hum during the low times and dubstep during rush hour. And the final step would be to broadcast it via radio, letting motorists tune in to the sound of their collective movement. Perfect.
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Aug 8, 2013 23:13
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Terminal Entropy posted:Feed it into a tone generator so you get a nice soothing hum during the low times and dubstep during rush hour.
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Aug 9, 2013 23:21
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Presto posted:Reminds me of that one Douglas Adams book where the guy was writing a program to turn natural rhythms into music. I suspect the Washington, DC area traffic would not be soothing. The Beltway is farting again 
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Aug 10, 2013 02:08
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Cichlidae posted:Q: What takes two weeks to make and looks awesome? Space Battleship Cichlidae
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Aug 10, 2013 21:56
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Another article on Dutch cycling culture. Apparently the UK are also trialling roundabouts with bike priority, in Berkshire! http://www.bbc.co.uk/news/magazine-23587916 The BBC posted:The fact that everyone cycles, or knows someone who does, means that drivers are more sympathetic to cyclists when they have to share space on the roads. vvv Well, that's disappointing, but possibly in London next year is better than never! Hippie Hedgehog fucked around with this message at 21:03 on Aug 11, 2013 |
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Aug 11, 2013 16:35
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Hippie Hedgehog posted:Another article on Dutch cycling culture. ...on a closed test site away from public roads. Don't get your hopes up too much! http://www.bbc.co.uk/news/uk-england-london-22350776
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Aug 11, 2013 16:59
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I am in the midst of building a massive re-vamp of the Milwaukee-area interstate system. I started on I-94 doing rebar work in 2010 and it hasn't slowed down any appreciable amount. A question I have is an age-old one from Ironworkers from years past, and that's "How do these geniuses expect us to put two bars in the same loving space?" I don't know how many times now we've found some congested area of bars and it's so hosed up you can't even get concrete under there. Up here we have had a few pretty awesome things happen with the freeway work, notably being the Rawson Avenue bridge being built up on falsework and rolled in with Mammoet heavy-movers. Everyone around here applauded the relatively small amount of time the freeway was shut down for, but the cost of doing that move had to have been almost as much as it would have cost building the bridge over wooden forms after the girders were rolled out like we usually do. I have heard a lot of poo poo-talking around here that SE Wisconsin now has the best roadway system in the country due to its young age. I haven't been to enough other states to confirm that rumor, can you shed any light on it?
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Aug 11, 2013 18:11
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Structurally, perhaps, but the geometric design leaves a lot to be desired in several places until the bigger reconstruction projects are finished.
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Aug 11, 2013 18:32
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I thought you guys might like this
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Aug 11, 2013 20:53
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jryand posted:I thought you guys might like this Is that real? Reminds me of this spiralling road in Tokyo, but without trains and not over water. https://maps.google.com/maps?q=toky...+Japan&t=h&z=17
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Aug 11, 2013 21:06
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jryand posted:I thought you guys might like this I call shenanigans on this, the traffic is moving too smoothly. It doesn't look realistic at all. 
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Aug 11, 2013 21:12
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The spiral is to gain enough height to go over a bridge, just like that Tokyo one (except its a full 360 degrees). It's in Shanghai. Edit: And have a Italian Loop nozz fucked around with this message at 21:18 on Aug 11, 2013 |
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Aug 11, 2013 21:14
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https://maps.google.com/maps?q=nanp...=h&z=18&iwloc=A it's here
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Aug 11, 2013 21:27
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Of course it's real, just a diorama effect video .gifed up.
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Aug 11, 2013 21:55
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Are we talking loops now? I really like the one in Rendsburg, Germany. After construction of the Kiel Canal (which allowed German ships to pass from the North Sea to the Baltic Sea without going through Denmark), the Germans realized that they wanted a rail bridge that was tall enough for sailing ships to freely go below the bridge. The result is the Rendsburg High Bridge, with a clearance of 42 meters above the water level. However, the existing railway station in the town was quite close to the canal, with no room for a direct descent from the bridge. The final result is the Rendsburg Loop. Oh, and the high bridge also accepts cars. There's a carriage suspended at street level below the bridge, which ferries people and cars across the Canal. 
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Aug 11, 2013 22:00
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A flying boat. Bravo, Germany, bravo.
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Aug 12, 2013 06:52
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California solved the "many parallel toll booths merging into few lanes" problem by a kind of modified ramp meter where the lanes each get a green in sequence. The lights are only active when traffic reaches a certain level. (This is actually what my suggestion from earlier was inspired by)
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Aug 12, 2013 13:04
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