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Cichlidae posted:Consider yourself lucky; if it were New England, we'd put a stop sign instead, and everyone would be driving 15 over the limit. I do wonder what the accident rates are like on the Merritt Parkway where they have these. I saw a backup of 5-6 cars trying to get out of the rest stop yesterday because the person in front had an old car and was waiting for a space big enough to accelerate in, that just wasn't going to happen.
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Apr 25, 2011 14:54
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Could a roundabout replace an intersection of two arterials? Should it? Why does the crazy Arc de Triomphe roundabout work without signals?
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Apr 25, 2011 17:33
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Saw this thread a couple of months ago, but decided to post here after spending 2 hours to move from here to there last wednesday. My only question is why, oh gods, why? My pet theory (with quite a lot of anecdotal evidence) is that this loop just grinds to a halt, making everyone in a 5 km radius miserable. Obs.: NE goes to the major interstate linking Rio de Janeiro to São Paulo. NW is the international airport, and the only entrance to a large residential island. E is the main commuting artery linking downtown to the suburb areas. The island I was trying to leave is the major federal university campus (about 65,000 students).
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Apr 25, 2011 21:25
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Why don't more intersections have the sensors that 1. Turn lights red so that emergency vehicles can get through, and 2. Check if cars are at small streets that intersect intersections late at night. People complain about pollution, A lot of pollution is made at people waiting for lights when there is no cross traffic.
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Apr 25, 2011 21:30
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smackfu posted:I do wonder what the accident rates are like on the Merritt Parkway where they have these. I saw a backup of 5-6 cars trying to get out of the rest stop yesterday because the person in front had an old car and was waiting for a space big enough to accelerate in, that just wasn't going to happen. The exclusion of most trucks certainly helps a bit in that regard. I... could get the accident rates, but I would not be allowed to show them to you! Suffice it to say that freeways on the whole have very low accident rates, and you're more or less taking your life into your hands if you drive on Route 1 from Greenwich to Milford. Mandalay posted:Could a roundabout replace an intersection of two arterials? Should it? Yes, it can. Multi-lane roundabouts, especially, work for this. Whether I'd actually want to use one depends on several conditions: volume balance, approach speeds, incoming/outgoing number of lanes, nearby signals and/or driveways that need platooning, bicycle volumes, and heavy vehicle percentage, off the top of my head. Every case is unique, and there are certainly cases where roundabouts would work better than signals. Mandalay posted:Why does the crazy Arc de Triomphe roundabout work without signals? Well, first off, it's not a roundabout. Traffic in the circle yields to incoming traffic. In theory, this is a bad idea, because it leads to gridlocking. In practice, Parisian drivers are some of the most aggressive in the first world, and they're so familiar with the Place de l'Etoile that they hardly blink an eye. I drove through it with my boss while I was there, and it was almost relaxing how smoothly everything went. Don't forget, too, that it doesn't have any lane lines. In practice, it's treated as about 6 lanes wide, so you can imagine the kind of capacity that affords. And sure, there are 12 streets entering it, but only a couple of them are really major, and they're complementary movements.
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Apr 25, 2011 22:04
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Cichlidae posted:What were they thinking? Probably "Oh god we need an interchange here and there is no space and the roads are crazy what do we do?!" I doubt an interchange like this would be built today (though engineers still manage to surprise me), mainly because of that nasty weave you mentioned. Heck, the whole thing is filled with nasty weaves. Definitely wouldn't meet design standards. Interesting. It would still back up to hell and gone, but at least you wouldn't have accidents there all the time. I never entirely understood why that road to the east was split the way it was, anyways. Millstone posted:hello residential suburbia! enjoy your new partial gantry! The people that used to live below us bought that grey house on the corner there about 8 months back. Traffic is backed up in front of their house about 75% of the day. Maybe they like the view of the partial gantry?
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Apr 25, 2011 22:16
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Magrov posted:Saw this thread a couple of months ago, but decided to post here after spending 2 hours to move from here to there last wednesday. Well, first off, we're talking about a major route in one of the largest cities in the developing world. I'm sure the freeway's not built to handle the volumes it's carrying currently. Two hours, though, is... a little excessive, to say the least! Looking at your second map, your theory is essentially correct. I'd say that the biggest pinch point there is the on-ramp from Av. Brg. Trompowski onto Ln. Vermelha. It's two lanes worth of traffic that get funneled down into one lane, then forced to merge into freeway traffic within 20 meters. Meanwhile, some traffic from Av. Pres. João Goulart has to weave across 3 lanes to get off at the next exit and go to the mainland. I see some ramp stubs on the bridge. Was the interchange redone (relatively) recently? Do you know what it looked like before? b0nes posted:Why don't more intersections have the sensors that 1. Turn lights red so that emergency vehicles can get through, and 2. Check if cars are at small streets that intersect intersections late at night. People complain about pollution, A lot of pollution is made at people waiting for lights when there is no cross traffic. 2. We try to do this wherever we can. In fact, many of our rural signals ONLY have detection on the side streets, not on the artery. Nearly all of our signals, regardless of location, go on flashing operation late at night, so cars on the side street just get a flashing red, which acts as a stop sign.
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Apr 25, 2011 22:16
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Cichlidae posted:Yes, it can. Multi-lane roundabouts, especially, work for this. Whether I'd actually want to use one depends on several conditions: volume balance, approach speeds, incoming/outgoing number of lanes, nearby signals and/or driveways that need platooning, bicycle volumes, and heavy vehicle percentage, off the top of my head. Every case is unique, and there are certainly cases where roundabouts would work better than signals. Cichlidae posted:Well, first off, it's not a roundabout. Traffic in the circle yields to incoming traffic. In theory, this is a bad idea, because it leads to gridlocking. In practice, Parisian drivers are some of the most aggressive in the first world, and they're so familiar with the Place de l'Etoile that they hardly blink an eye. I drove through it with my boss while I was there, and it was almost relaxing how smoothly everything went. b0nes posted:2. Check if cars are at small streets that intersect intersections late at night. People complain about pollution, A lot of pollution is made at people waiting for lights when there is no cross traffic. Roundabouts would solve this problem 
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Apr 25, 2011 22:17
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you ate my cat posted:I never entirely understood why that road to the east was split the way it was, anyways. The trend in the 1950s and '60s was to put in directional movements for everything. Basically, safety wasn't a big priority back then, so they tried to give each movement its own ramp/roadway and maximize capacity. These days, we're much more interested in normalizing intersections and meeting driver expectancy. Sure, it cuts the capacity, but you won't have people dying monthly at a bad intersection. Mandalay posted:Do you have any case studies of successful arterial x arterial signaled intersection -> roundabout conversions in the US? Actually, unsuccessful conversions would be interesting too. I don't have anything local, unfortunately. Our definition here of an arterial is rather loose, so it wouldn't be terribly applicable in most other places. Nationally, though, they're all over. Check out this one in Vail. It was signalized before, and constantly backed up. Since the roundabouts were installed, traffic has been much smoother. There is a city in the Midwest with roundabouts at just about every major intersection... Edit: CARMEL, INDIANA Cichlidae fucked around with this message at 21:01 on May 2, 2011 |
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Apr 25, 2011 22:24
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Mandalay posted:
And i am talking about the single lane ones not the ones like in that episode of the Simpsons.
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Apr 25, 2011 22:30
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Cichlidae posted:The trend in the 1950s and '60s was to put in directional movements for everything. Basically, safety wasn't a big priority back then, so they tried to give each movement its own ramp/roadway and maximize capacity. These days, we're much more interested in normalizing intersections and meeting driver expectancy. Sure, it cuts the capacity, but you won't have people dying monthly at a bad intersection. Interesting. I guess that explains this split slightly farther east as well. I hate driving near my house. By the way, this thread has been fascinating and has allowed me to pepper my friends and family with traffic tidbits. Keep it up!
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Apr 25, 2011 23:01
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b0nes posted:Meh maybe up in Pasadena, California there is one on Glenarm street. Almost got ran into a few times pecause people don't know what the gently caress. I've used it, how is it better than a 4 way stop? For one, you don't have to stop at a roundabout. I personally hate stop signs in 4-way intersections. Here's a roundabout I really like in Irvine, CA: http://maps.google.com/maps?f=q&sou...2,0.003841&z=19
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Apr 25, 2011 23:18
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Plus you only have to look in one place to know if you're safe. As a European driving in America, I find your all-way stops loving terrifying.
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Apr 25, 2011 23:27
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Wolfsbane posted:Plus you only have to look in one place to know if you're safe. As a European driving in America, I find your all-way stops loving terrifying. I don't know, from the number of people I've seen ignoring all directional signage and going the wrong way around roundabouts, 4-way stops aren't quite as scary to me 
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Apr 25, 2011 23:28
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you ate my cat posted:Interesting. I guess that explains this split slightly farther east as well. I hate driving near my house. Exactly. Everything's channelized, islands all over. Sure, it may need a dozen "DO NOT ENTER" signs, but the capacity's increased by 15%! grnberet2b posted:I don't know, from the number of people I've seen ignoring all directional signage and going the wrong way around roundabouts, 4-way stops aren't quite as scary to me Don't worry, those people will get weeded out one way or another...
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Apr 26, 2011 01:00
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Well here's a roundabout that didn't work out. This used to be a 4-way stop in the early 90s, which was changed to a roundabout around 1995 or so. http://maps.google.com/maps?f=q&sou...009645&t=h&z=17 The main problem is that 90% or more of the traffic is cars on NB Charles turning left onto 695/83, or cars on WB Bellona turning onto SB Charles.  And as a bonus, on the on-ramp coming off the circle there are businesses, which means the ramp needs to be 2-way. And traffic exiting the businesses has to turn left across traffic entering the highway. So it's no surprise then that they're [url=http://apps.roads.maryland.gov/WebProjectLifeCycle/ProjectInformation.aspx?projectno=BA9775A3]ripping out the whole thing and putting in a couple signals: quote:SHA is making major improvements to the I-695 interchange at Charles Street (MD 139) in the Towson area of Baltimore County. This project also includes major rehabilitation of the bridge carrying I-695 over I-83 (Baltimore-Harrisburg Expressway) and Baltimore's Light Rail line. If the businesses on the old ramp weren't complicating things enough, there's also the Baltimore Light Rail line running through the construction zone (and they're rebuilding the bridge over it), as well as the interchange with NB I-83 and a number of side streets close to the area.
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Apr 26, 2011 01:58
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Cichlidae posted:Well, first off, we're talking about a major route in one of the largest cities in the developing world. I'm sure the freeway's not built to handle the volumes it's carrying currently. Two hours, though, is... a little excessive, to say the least! Ln Vermelha/Av. Pres. João Goulart was built on the 90's. Originally all traffic to/from São Paulo and the suburbs had to come through Av. Brasil, to the east. I guess it worked, since both arteries are relatively uncluttered nowadays. If you are driving through Ln. Vermelha, the traffic flows. It's getting on/off it that takes so long. They are building a suspended bridge on the Fundão Island to southbound Ln. Vermelha, away from this hellhole. That should relieve some of the traffic there. It'll also mean I'll never ever ever have to drive there too.
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Apr 26, 2011 03:30
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Mandalay posted:For one, you don't have to stop at a roundabout. I personally hate stop signs in 4-way intersections. Here's a roundabout I really like in Irvine, CA: http://maps.google.com/maps?f=q&sou...2,0.003841&z=19 Ok I didn't know there were any in the US. What do you call this then? 
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Apr 26, 2011 10:08
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b0nes posted:Ok I didn't know there were any in the US. What do you call this then? Retarded? I'm sure Chichlidae will answer your question properly, but to me it looks like some stupid city council's idea of a brilliant traffic-calming measure.
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Apr 26, 2011 10:38
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b0nes posted:Ok I didn't know there were any in the US. What do you call this then? It's really just slapping an island in the middle of an all-way stop. It's not a very good design, because trucks would have to drive the wrong way around the circle to take a left. The signage is all wrong, there are no stop bars, and why is there a little strip of pavers in the middle of the island? Do they expect people to walk out there? It's a pretty obvious retrofit of an existing AWSC intersection. They didn't even bother to bump out the curbs to force a better alignment. Just lazy.
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Apr 26, 2011 12:38
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b0nes posted:Ok I didn't know there were any in the US. What do you call this then? That's terrible. I lived near some similarly bad roundabouts in college, but with much lower traffic flows.  There's a nicely designed roundabout in Long Beach, but I've never driven through it. Because it incorporates CA-1, it might get really busy during rush hour. Cichlidae, how do you keep people from cheating onto the outer traffic circle if the roundabout gets backed up? 
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Apr 26, 2011 16:57
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Mandalay posted:That's terrible. I lived near some similarly bad roundabouts in college, but with much lower traffic flows. This might be apocryphal, but supposedly that whole quadrant of Berkeley is designed to be as difficult as possible to transit by car, in order to encourage people to take the main roads (MLK, California, etc.) instead of driving through neighborhoods. For those that don't know the area, a huge section of Berkeley is a tangled warren of awful roundabouts like the one quoted above and bizarre barriers that turn what could easily be through streets into a network of dead ends.
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Apr 26, 2011 17:34
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Bold Robot posted:This might be apocryphal, but supposedly that whole quadrant of Berkeley is designed to be as difficult as possible to transit by car, in order to encourage people to take the main roads (MLK, California, etc.) instead of driving through neighborhoods. For those that don't know the area, a huge section of Berkeley is a tangled warren of awful roundabouts like the one quoted above and bizarre barriers that turn what could easily be through streets into a network of dead ends. If you are visiting that area of berkeley, the parking garages (which you should use, since street parking is very scarce) are on major roads anyway, and if you live there you should only have to drive when leaving town anyhow--it's a very walkable city. Socket Ryanist fucked around with this message at 18:29 on Apr 26, 2011 |
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Apr 26, 2011 18:18
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Mandalay posted:That's terrible. I lived near some similarly bad roundabouts in college, but with much lower traffic flows. Why wouldn't I let them cheat onto it? May as well use a road if it's available It doesn't make a complete circle, and it's a longer drive than the inner circle for most routes, so I'd be more inclined to use the inner circle if there wasn't much traffic. But yeah, it's mostly commercial, it's two-way, and it could cut congestion if used as a bypass. Why not?
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Apr 26, 2011 22:08
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http://www.youtube.com/watch?v=Bj_1KcGLwFQ&feature=player_embedded America + roundabouts = ?
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Apr 27, 2011 00:18
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Baronjutter posted:http://www.youtube.com/watch?v=Bj_1KcGLwFQ&feature=player_embedded They put in a round about near a college around here and I drove it about a dozen times now and about half the time I will see someone sitting there with their blinker on or a old person going around it the wrong way. It just seems to me its old people because I got my buddies to drive through it just to see if they knew how and they did it perfect with and without traffic there.
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Apr 27, 2011 02:14
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smackfu posted:I do wonder what the accident rates are like on the Merritt Parkway where they have these. Cichlidae posted:The exclusion of most trucks certainly helps a bit in that regard. I... could get the accident rates, but I would not be allowed to show them to you! b0nes posted:Ok I didn't know there were any in the US. What do you call this then?
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Apr 27, 2011 04:13
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Cichlidae posted:Why wouldn't I let them cheat onto it? May as well use a road if it's available I'm trying to find an example of where an intersection is superior to a roundabout but failing. It seems to me that in an ideal world, it would be {no controls}->{roundabout}->{grade-separated}. Pheloz posted:They put in a round about near a college around here and I drove it about a dozen times now and about half the time I will see someone sitting there with their blinker on or a old person going around it the wrong way. It just seems to me its old people because I got my buddies to drive through it just to see if they knew how and they did it perfect with and without traffic there. This seems appropriate: Cichlidae posted:Don't worry, those people will get weeded out one way or another...
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Apr 27, 2011 06:20
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GWBBQ posted:IIRC, as of a few years ago the Merritt Parkway had sustained a fatality rate of one death per mile per year for at least the past 10 years. This was according to the CT Post, so the numbers may have been rounded up a bit to make a scary headline. A good friend of mine is a Weston firefighter and told me they have late-night rollovers into the woods (level or uphill if you're lucky) in Westport at least weekly along their few miles, so it's entirely believable. Wow, that does seem pretty high. In Rhode Island, we had about one rollover every three days statewide. GWBBQ posted:If I field a FOIA request, would that be disclosed? Our position is that this information is not obtainable even by FOIA or subpoena. It's not dangerous information and it doesn't make us look bad, but lawyers and the public tend to misinterpret it. We can't afford to send engineers to every accident case to explain why the intersection isn't really dangerous. GWBBQ posted:An Insane Stunt Bonus waiting to happen. But can you stick the landing?
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Apr 27, 2011 12:47
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I suppose it helps too that the Merritt Parkway on-ramps do seem especially dangerous. So people take a lot more care than a typical merge. And there is only a certain level of traffic where they are really bad, where the cars are going 65 and there are small gaps between them.
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Apr 27, 2011 15:33
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Mandalay posted:I would be worried about speeds on the outer ring for cars cutting from SE to NE, for example, but as you said, it is commercial anyways. It just feels inelegant I live a few blocks form the LB Traffic Circle (and have posted about it in this thread before). The Outer Circle isn't really an option if you want to zip through unhindered. There are lights and stop signs all over the place that make it slower to use unless the main circle was shut down. If you wanted to go from the southbound Los Coyotes Diagonal (the street at the NW portion of the photo) to northbound Lakewood Blvd (the top of the circle), that is about the only time the Outer Circle is handy.
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Apr 27, 2011 18:32
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smackfu posted:I suppose it helps too that the Merritt Parkway on-ramps do seem especially dangerous. So people take a lot more care than a typical merge. And there is only a certain level of traffic where they are really bad, where the cars are going 65 and there are small gaps between them.
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Apr 27, 2011 19:19
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The most jarring thing in that picture for me is seeing Main Avenue instead of Main Street.
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Apr 27, 2011 19:44
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GWBBQ posted:The entrances are really bad, but nothing in the world is as much fun as trying to take this exit when traffic is moving along at 70mph. It's come up in this thread before, but take a look at the entrances and exits at that interchange if you haven't. At least that interchange is getting redone (when we have money).
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Apr 27, 2011 21:51
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Cichlidae posted:At least that interchange is getting redone (when we have money). That intersection is fun as hell.
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Apr 28, 2011 03:33
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Just wondering what you think of this upgrade in Melbourne, Australia. It's a pretty major intersection, with the streets below connecting to the overpass and this seems to have helped a bit but those streets below still look pretty messy. http://en.wikipedia.org/wiki/West_Gate_Freeway#2008_Upgrade Here is the under construction image from google maps and an image from April 6th 2011 on Nearmap.com below it.  (Click for big) A drive through simulation now, after completition: http://www.youtube.com/watch?v=0_fE1J8pvKs&feature=player_detailpage#t=84s Project render video of the new interchange: http://www.youtube.com/watch?v=0omjg_zElbQ&feature=player_detailpage#t=156s This project finished last year, I don't drive on that section of road often (unless going to the airport) but it can be a little confusing. I think the additional flyovers helped but the ground level layout is still pretty nasty.
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Apr 28, 2011 05:34
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drunkill posted:Just wondering what you think of this upgrade in Melbourne, Australia. It's a pretty major intersection, with the streets below connecting to the overpass and this seems to have helped a bit but those streets below still look pretty messy. That is some excellent freeway design. The collector-distributor roadways get rid of weaving on the main line and simplify exits. Is this a ramp meter on the C-D roadway? I suppose it would help to manage weaving downstream.  And that simulation video is amazingly good. I wonder how much it cost! Must have taken months.
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Apr 28, 2011 12:45
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Cichlidae posted:Is this a ramp meter on the C-D roadway? I suppose it would help to manage weaving downstream. C-D roadway? If you mean that bottom most lane? Looks like that is the 'slipway' or something for the onramp about a kilometer to the east, when you turn on from Kings Way. (you can turn on stream names in Nearmap by hovering over the green 'photomap' button in the topmost left and check the streep map box.) And that is also a very busy streach of roadway. On either side of this upgraded flyover section you have 2 or 3 major interchanges/tunnels bridge ramps within 2-3 kilometers. Cichlidae posted:And that simulation video is amazingly good. I wonder how much it cost! Must have taken months. Now, for the eastern suburbs, what do you think of this 3-tired 3-way (6 way i suppose) road interchange? This is part of the new Eastlink tollway road. If you are heading south east and you want to reach the top-most road you don't turn until after the overpasses, which seems a little odd and due to the hill the turn-off has to climb it can be missed if you are looking to turn before you go past the flyovers.  (Click for embiggen'd) Just to the north (scroll up a bit) you can see the intechange of the M1 (Monash) and Eastlink which is quite large and during construction the roads were re-routed a few times to let traffic continue. The land for the eastlink intersection here has been reserved for like 15 or more eyars before it was built (probably 30 years, I have no clue) because it used to be farmland/empty grass fields. A few houses may have been bought and demolished but not that I know of, so it's a pretty large intersection but kinda tight too, in a way.  (Click for large image) drunkill fucked around with this message at 17:42 on Apr 28, 2011 |
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Apr 28, 2011 17:21
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drunkill posted:
It's hard for me to make sense of the "backwards roads" in the Queen's realm. I'm just used to the standards of roadways in the rest of the world.
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Apr 28, 2011 19:02
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drunkill posted:C-D roadway? If you mean that bottom most lane? Looks like that is the 'slipway' or something for the onramp about a kilometer to the east, when you turn on from Kings Way. (you can turn on stream names in Nearmap by hovering over the green 'photomap' button in the topmost left and check the streep map box.) Right right, but it expands into two lanes and has a stop bar right there. Is there a signal there, on the ramp? drunkill posted:Now, for the eastern suburbs, what do you think of this 3-tired 3-way (6 way i suppose) road interchange? This is part of the new Eastlink tollway road. If you are heading south east and you want to reach the top-most road you don't turn until after the overpasses, which seems a little odd and due to the hill the turn-off has to climb it can be missed if you are looking to turn before you go past the flyovers. Cool, that's a combination of a diamond and a quadrant interchange. A bit inconvenient for people going to/from Heatherton Road, but since it's residential, I'm sure they appreciate the low amount of cut-through traffic that results. The reason the turn-off is away from the intersection is to provide some space between the signals for adequate coordination and storage. See how all three signals are about evenly spaced? drunkill posted:Just to the north (scroll up a bit) you can see the intechange of the M1 (Monash) and Eastlink which is quite large and during construction the roads were re-routed a few times to let traffic continue. Other than the lack of access NB -> EB and WB -> SB, it's a very complete interchange. The way the on-ramp from Police Road is set up minimizes weaving. Classy little interchange.
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Apr 29, 2011 02:14
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