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Fantastic thread! I would love a discussion on Traffic Jams. What causes them? How do you model them? Do they have predictable flow and what do traffic engineers due to prevent them? (My pet theory is that they are caused by people driving in the wrong lane. Granny McGee staying in the second from the left lane when she should be in the right. Also, big trucks prevent people from merging/passing. What do you think? Any validity to that?)
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Aug 1, 2009 05:09
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Cichlidae posted:Seriously, truck drivers have some impressive turning skills. The only person I saw drive on it was, you guessed it, an elderly woman who had no idea what was going on. "Huh? Why's there brick in the middle of the road? Let me go run over some more orphans and girl scouts." Yeah, the only time I run into a problem is when I'm all the way to the back with my tandems. Which I hate loving running like that because in effect, I now have a 53 foot wheelbase on the trailer. So I turn and a week later the trailer follows.
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Aug 1, 2009 05:22
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sc0ticus posted:Fantastic thread! Hey sweet, other people are using Granny McGee now! I'll give you a full explanation of what causes congestion and how we can prevent it on Sunday. I have a reunion tomorrow, so I won't be in. As usual, keep on asking questions! I get to all of them eventually. Thanks for your interest, everyone!
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Aug 1, 2009 05:44
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A couple more questions. First, is there a difference between a transportation engineer and a traffic engineer? Also, how hard (assuming you have the degree and certifications required) would it be to attain a job working in a TMC? I've always thought that'd be a cool job, but it seems like there wouldn't be many openings. Another turn off was according to some engineers where I co-op now is that transportation engineers are easy to come by, so job security is kind of an issue. I was just wondering what your thoughts were on that.
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Aug 1, 2009 07:17
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smackfu posted:Unless he meant the ramp only? Nope... all the way from Cheshire infamous construction to Waterbury is 45... I'll snap a pic today if I'll remember Edit: I stand corrected, its 55... 45 must have got stuck in my head from construction time. ItchyDroopy fucked around with this message at 16:05 on Aug 1, 2009 |
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Aug 1, 2009 15:22
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sc0ticus posted:I would love a discussion on Traffic Jams. What causes them? How do you model them? Do they have predictable flow and what do traffic engineers due to prevent them? When the road/highway gets near capacity which happens during peak hours, it doesn't take much to cause a jam. Lane changing, merging, talking on your cell phone, changing radio stations, etc can cause slow downs which cause a ripple effect. Hitting brakes is a psychological distraction to other drivers which probably does the worst damage to interrupt flow. Leaving enough room between cars can alleviate problems by allowing merging or lane changing vehicles to do their thing without sudden braking. Driving in the wrong lane? When you get near capacity there is no wrong lane. Most traffic will be running near the same speed and more densely packed than is desired. On a four lane highway that is operating normally, a person driving slowly in the "fast lane" will prevent speedier drivers from driving what they think they have the right to drive. That does not cause traffic jams unless you get those speedier drivers tailgating and driving recklessly. More often than not you get somebody tailgating or trying to cut off the wrong person. Nobody can drive faster than the flow of traffic, so it doesn't solve anything to get pissed at the guy in front of you for driving slow when he is stuck behind slower drivers like yourself. The best thing to do is to relax and leave space and avoid braking (unless you absolutely need to)!
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Aug 1, 2009 16:37
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When I listen to my ipod through the radio and am sitting at an intersection during the yellows before my red turns green the radio will static moderately. It happens at every intersection, and also happens in my friends car. What's the deal?
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Aug 1, 2009 16:41
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ItchyDroopy posted:Edit: I stand corrected, its 55... 45 must have got stuck in my head from construction time.
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Aug 1, 2009 16:48
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What the heck is going on here? I drive through this abortion at least once a week and get in a near accident every time.
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Aug 1, 2009 21:04
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Cichlidae posted:We've got a bit of free time, so here's a quick rundown of the agencies in the USA most responsible for transportation-related policy. Great thread! I'm a civil engineer that works mostly on land development projects(bluhhhhh). My company's done some roadway improvement stuff too, but it's been pretty minor. Out of curiosity, I'm thinking about getting into the transportation side of things since I don't much like what I'm doing now. I'm planning on going back for a master's degree with a transportation focus, and was wondering if you had any tips for getting into either DOTS or transportation divisions in some larger companies. Also, a little more on topic, do you think that the Green book is abused a little bit when dealing with smaller local roads? For example, in my area we have to design local roads to municipal standards. Fair enough. However, most of these criteria are pulled out of the green book, which to me is overkill for roads that are like 25-35 mph tops. You've got poo poo like superelevation, extra wide lanes and so forth on these residential roads, and to me it seems like a safety issue. You've designed a road to be "safe" for cars flying along at high speeds, and then people of course do just that through residential neighborhoods. Whereas older neighborhoods with narrow streets, sharp turns and so forth seem to have people driving at an overall lower speed when I drive on them. Do you have an opinion, or have you seen any data on this type thing (pedestrian/vehicle accidents by neighborhood and such)? I don't know, it just doesn't strike me as particularly safe.
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Aug 1, 2009 21:50
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Neutrino posted:On a four lane highway that is operating normally, a person driving slowly in the "fast lane" will prevent speedier drivers from driving what they think they have the right to drive. That does not cause traffic jams unless you get those speedier drivers tailgating and driving recklessly. More often than not you get somebody tailgating or trying to cut off the wrong person. I'm with you, just chill out and turn the music up. But I think these 'entitled' people cause problems because of excessive tailgating and braking when they're following slower drivers. This in turns causes more stop and go behavior, which could be ameliorated by the slower drivers letting the aggros pass. Just my little theory in any case.
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Aug 1, 2009 23:14
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Someone posted earlier about traffic signals in Japan, so I figured I'd fill in a bit. Most of the signals here are "jisa shiki" (時差式), time difference style; in other words, your standard "this lane waits this long, every time, regardless of traffic flow". Especially common in cities at intersections that have crosswalks (aka the vast majority). After jisa shiki, the most common by far is "押しボタン式”, osi botan shiki, aka "press a button style" where they nothing changes until someone pushes a button, in which case the current cycle is interrupted. There are a couple more, but I've only seen them a few times. A lot of times (especially in cities), particular signals at large intersections will have their shiki written on a sign that hangs under the light, so it's easy to see what pattern they're using. Sheep fucked around with this message at 02:15 on Aug 2, 2009 |
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Aug 2, 2009 01:46
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This thread is awesome. I would like to use it to bitch about Richmond, VA. As far as I can tell, no traffic engineer has been involved in Richmond's transportation ever. Most of the traffic lights have no sensor and seem to be timed completely independently. Driving down Broad St. is a nightmare at night; you stop at almost every single light and wait for a full cycle even if you are the only car on the road. Monument Ave. is a great example of why American's can't handle roundabouts. It seems like whoever laid out that road saw a blurry picture of a roundabout once and decided to create several abortions of attempts at them around the monuments. Here's one of their variations:  Incoming traffic is supposed to yield, but both lanes of Monument Ave. can continue straight through. The green car above entered the outer lane of the circle, and the red car is allowed to pass straight through on a collision course. Who's supposed to yield? It's an exciting mystery every time! Just down the street is this intersection:  It is just a stoplight, but is confusing as hell since it looks exactly like one of the free-for-all roundabouts down the street. I've been the green car in the above scenario and almost cut off the red car, thinking "traffic circle" not "retarded stop light intersection cleverly disguised as a traffic circle." For bonus points, notice the no man's land in blue. There is no legal way for the cars parallel parked there to have gotten there, since Monument is one way going east from the roundabout. I guess it's possible that traffic used to travel both ways, but I'd like to think the same idiot who designed three or four fake roundabouts with completely different, ambiguous right-of-way rules within blocks of each other just added another mistake for fun.
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Aug 2, 2009 02:33
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smackfu posted:No worries, everyone always drives 80 through there anyway, since it's straight and flat. They definitely did a nice job on that stretch.
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Aug 2, 2009 05:50
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Cichlidae posted:The plows here are nasty. They knock over mailboxes so often that people have taken to sticking a 4' by 8' piece of plywood in front of the box in winter to improve visibility. They also peel up pavement markings, carve up islands, and even rip out train tracks. That was a costly mistake.
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Aug 2, 2009 17:35
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OP! Thank you for taking time to answer all our questions so far. This thread has been very informative. Now I'd like to add a question to the pile: You've made your disdain for speed limits quite plain. However, surely there are situations where it would be beneficial to have traffic drive slower (residential neighborhoods come to mind). What are some of the ways to get traffic to slow down without imposing an arbitrary speed limit on roads that were clearly designed for much higher speeds? I can think of two ways on my own. If I may illustrate them with a story, and render my opinion on which is more effective, perhaps you could correct me? I grew up in Phoenix, a city that lauds itself for its urban planning. (Signs when you enter town call it "the best run city in the world.") Anyway, they have lots of nice straight streets set up in a grid system, and through the residential areas, to slow traffic down, they install the dreaded speed bump. My step-brother (before he was my step-brother), actually organized his boy scout troop to petition the town to install speed bumps on his street. My dad would curse his name every time we drove home. Seems to me such a thing serves to piss off the residents as much as it would slow traffic. Thoughts? On the other side of the coin, there was a certain side street that was very conveniently placed to avoid rush hour traffic on my way to school. Once, when driving that road, I noticed that the town had apparently either sold or given a portion of the road to one of the property owners, making a small spit of land stick out into the once-straight road, effectively making the road curve a bit. This in turn made traffic slow down out of the necessity of avoiding driving over the guy's lawn. This would seem to be a more effective way of slowing traffic down, and has the added benefit of not making it obvious that that's what's happening, so you don't piss off the motorists. What's your take on these, and other solutions to making people slow down through residential areas, or other situations where you need traffic to drive slower? EDIT: Oh, and just to make it clear, I do not think that Phoenix is the paragon of urban planning, as the city claims to be. The place is a poo poo-hole, the very worst example of urban sprawl outside of L.A. The way the city is laid out makes it impossible to find your way around because every loving street corner looks the same. The city is run by idiots and I am so glad I don't live there anymore. Silver Falcon fucked around with this message at 18:13 on Aug 2, 2009 |
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Aug 2, 2009 17:54
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sc0ticus posted:Fantastic thread! Alright, it's time to learn about Congestion! There are two kinds of congestion: recurring, and non-recurring. RECURRING CONGESTION This kind of congestion occurs on a regular basis (duh), usually between 6-9 AM and 3-6 PM on weekdays, and around noon on weekends. It's a result of demand exceeding capacity. Remember how roads are most efficient at LOS E, right at the edge of breakdown? That is what scientists would call an unstable equilibrium. Add just a few more cars, and you hit the breakpoint. I'm posting this graph again so you can see; the lower-right graph best shows what I'm talking about.  Once you hit that breakpoint (volume = capacity), drivers get uncomfortable and start slowing down. You see a wave of brake lights. Cars get closer together, capacity drops since everyone's moving slower, and the jam spreads backward. This applies to all roads and all kinds of congestion, even red lights. The big difference is that, in recurring congestion, it's caused by demand increasing, while in non-recurring, it's caused by capacity decreasing.  As you can see, this queue of LOS F, represented by red, spreads upstream. The length of the queue is dependent on two factors: the flow rate upstream, usually about 2200 veh. per lane per hour at LOS E, and the rate at which traffic can depart from a standing queue (green cars to the right), usually around 1500 vplph. When the number arriving is greater than the number leaving, then the queue will keep growing. When it's less, it'll shrink and eventually disappear. For recurring congestion, this only happens once the peak hour is over and the volume drops significantly. NON-RECURRING CONGESTION This has a lot of causes: a traffic accident, construction closing a lane or a ramp, bad weather, an elephant walking down the middle of the road... Like I said, the capacity of the road drops. For as long as the capacity is lower than the demand, the queue will build. At some point, it'll be restored, and the queue dissipates. Here's a handy graph showing how we estimate queues, and I'll even leave out the Greek letters, just for you!  The X axis represents time, and the Y axis represents a quantity of cars. Therefore, the slope of lines, cars/time, is a rate. When the arrival rate exceeds the departure rate, a queue builds up, shown in red. Eventually, the departure rate increases, and the queue dissipates. The rest should be self-explanatory, but let me know if you don't get anything. So the last part of the question is how do we prevent them. For any kind of congestion, there are two means of prevention: increasing capacity and lowering demand. Increasing capacity means adding more lanes, adding a bypass, or increasing the speeds. Reducing demand means getting cars off the road, whether it's by putting people on buses, getting them to carpool, or putting up tolls.
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Aug 2, 2009 18:19
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nbakyfan posted:A couple more questions. First, is there a difference between a transportation engineer and a traffic engineer? Traffic engineering is a subset of transportation engineer. A transportation engineer could deal with planes, highway design, maintenance, whatever. Traffic engineers specifically deal with traffic flow. quote:Also, how hard (assuming you have the degree and certifications required) would it be to attain a job working in a TMC? I've always thought that'd be a cool job, but it seems like there wouldn't be many openings. Another turn off was according to some engineers where I co-op now is that transportation engineers are easy to come by, so job security is kind of an issue. I was just wondering what your thoughts were on that. Most of the people in the TMC weren't specifically trained for it. They're all contractors, in fact. Working in the TMC requires a good deal of computer skills, moreso than engineering knowledge. As for getting a job there, good luck, because there are only a very limited number of positions.
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Aug 2, 2009 18:23
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Neutrino posted:When the road/highway gets near capacity which happens during peak hours, it doesn't take much to cause a jam. Lane changing, merging, talking on your cell phone, changing radio stations, etc can cause slow downs which cause a ripple effect. Hitting brakes is a psychological distraction to other drivers which probably does the worst damage to interrupt flow. Leaving enough room between cars can alleviate problems by allowing merging or lane changing vehicles to do their thing without sudden braking. Leaving space is recommended, but it doesn't work too well in New England. In heavy traffic, a 20 foot gap is plenty for someone to cut in front of you. One more thing that neither of us mentioned is one interesting by-product of shockwave theory: the queue itself moves. If the congestion is caused by a car accident, the site might be long cleaned up by the time the queue dissipates. This was a big problem at the TMC, because we'd put up signs telling people that the congestion was caused by an accident, then they wouldn't see any wreckage and would assume we were lying.
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Aug 2, 2009 18:26
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thehandtruck posted:When I listen to my ipod through the radio and am sitting at an intersection during the yellows before my red turns green the radio will static moderately. It happens at every intersection, and also happens in my friends car. What's the deal? There's a lot of electrical activity at signals. You've got the vehicle detection, which is projecting a pretty strong magnetic field right at your car, you could have RC pre-emption, some signals have wireless links... all in all, you're looking at about 600 Watts for the whole thing, much more with the old incandescent lights. I don't know if anyone here works with EMF interference, but having that much power directed at your car seems like it might break up a weak radio signal.
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Aug 2, 2009 18:29
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Hofp posted:Whereas older neighborhoods with narrow streets, sharp turns and so forth seem to have people driving at an overall lower speed when I drive on them. Just wanted to mention that drivers drive slower on narrow streets and even more so when there are cars parked on the side. The added benefit is a more pedestrian friendly area. Not only are speeds reduced but the cars parked along the street act as a buffer. I have a question about 45 degree angle parking (such as http://4.bp.blogspot.com/_RJ0lXJtyLoc/SGK2o6jkR4I/AAAAAAAAACc/6s9huHOvuCE/s400/angle%2Bparking.jpg). You can of course find this parking everywhere but more specifically I'm wondering about when it's in this sort of situation: http://maps.google.com/maps?f=q&sou...003484&t=h&z=19 Why is parking on streets like that always designed so one has to back up out of their space? It's always a pain in the rear end to see oncoming traffic. What do you have to do to implement a space where cars back in to the spaces (I think this may be called Back-in/Head-out Angle Parking)? Do you need to roads to be wider to give cars space to back up? Have drivers who are parking momentarily hold up traffic? I like the back-in/head-out parking because it's safer exiting and since the door opens towards the road acting as a buffer (there we go again) between your child and the street.
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Aug 2, 2009 18:32
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Os Furoris posted:What the heck is going on here? Oh jeez, those are some really tight curves. Seeing as it's in Brazil and how many lanes there are, I'm assuming there's a lot of traffic, too. I see the bump strips they put across the freeway to get you to slow down, and solid lane lines so you don't try to change lanes in the curve. I'm going to go ahead and say the main problem there's how tight the curve is.
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Aug 2, 2009 18:32
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Hofp posted:Great thread! I'm a civil engineer that works mostly on land development projects(bluhhhhh). My company's done some roadway improvement stuff too, but it's been pretty minor. Practical experience helps a lot, but it's mostly knowing the right people and being lucky. The job market is completely different now from how it was a year ago. I'd either wait for it to get better, or look for a bridge to collapse somewhere - the local DOT is sure to hire a ton of engineers if that happens. That's how all my bosses got hired, in fact. quote:Also, a little more on topic, do you think that the Green book is abused a little bit when dealing with smaller local roads? For example, in my area we have to design local roads to municipal standards. Fair enough. However, most of these criteria are pulled out of the green book, which to me is overkill for roads that are like 25-35 mph tops. You've got poo poo like superelevation, extra wide lanes and so forth on these residential roads, and to me it seems like a safety issue. You've designed a road to be "safe" for cars flying along at high speeds, and then people of course do just that through residential neighborhoods. Whereas older neighborhoods with narrow streets, sharp turns and so forth seem to have people driving at an overall lower speed when I drive on them. Do you have an opinion, or have you seen any data on this type thing (pedestrian/vehicle accidents by neighborhood and such)? I don't know, it just doesn't strike me as particularly safe. I'll be doing a post on traffic calming soon that will address this. The Green Book is guidelines, remember, not rules. I wouldn't argue that roads should be built below standards just to lower speeds, as it can introduce safety issues and hamper future expansion. As traffic engineers, though, we have special tricks that can slow people down without sacrificing safety.
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Aug 2, 2009 18:39
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sc0ticus posted:I'm with you, just chill out and turn the music up. But I think these 'entitled' people cause problems because of excessive tailgating and braking when they're following slower drivers. This in turns causes more stop and go behavior, which could be ameliorated by the slower drivers letting the aggros pass. Just my little theory in any case. In this case, the law is there for a reason. Everyone is supposed to drive in the rightmost travel lane, using the left lanes only to pass. This ends up being the safest arrangement. If you think the guy speeding in the left lane is a problem, let him get pulled over and slapped with a $500 ticket. It's better than getting rear-ended when a deer runs across the road or shot in the head out of road rage.
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Aug 2, 2009 18:42
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Cichlidae posted:Oh jeez, those are some really tight curves. Seeing as it's in Brazil and how many lanes there are, I'm assuming there's a lot of traffic, too. I see the bump strips they put across the freeway to get you to slow down, and solid lane lines so you don't try to change lanes in the curve. I'm going to go ahead and say the main problem there's how tight the curve is. This talking about Brazil brought up a memory of a video I watched in an urban planning class (taught by the former planning director of SLC. Really.. this guy is a genius. But I digress..). The video was about a city in Brazil that implemented tons of changes to reduce congestion, sprawl, pollution, etc. It was fascinating. I'll try to find out what it was and let you guys know.
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Aug 2, 2009 18:44
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ManicJason posted:Monument Ave. is a great example of why American's can't handle roundabouts. It seems like whoever laid out that road saw a blurry picture of a roundabout once and decided to create several abortions of attempts at them around the monuments. Here's one of their variations: Wow, that is a pretty bad design. It could be easily fixed, too, with a turbo roundabout (and a much smaller footprint; for roundabouts, smaller is better.) What's a turbo roundabout? It carries the same capacity as what's there now, but cuts the number of conflict points and results in smoother operation. Behold! (cribbed from Wikipedia)  quote:Just down the street is this intersection: And that's just nasty. I can see exactly what you mean, and that's a very real problem. It's unfortunate that they probably have to bow to historic preservationists, otherwise they could move the statue to the median and normalize the intersection.
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Aug 2, 2009 18:48
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Billy Maize posted:This talking about Brazil brought up a memory of a video I watched in an urban planning class (taught by the former planning director of SLC. Really.. this guy is a genius. But I digress..). The video was about a city in Brazil that implemented tons of changes to reduce congestion, sprawl, pollution, etc. It was fascinating. I'll try to find out what it was and let you guys know. Ok this was easier to remember than I thought it would be. It's about Curitiba, Brazil. It's called "A Convenient Truth: Urban Solutions from Curitiba, Brazil" Here's a trailer: http://www.youtube.com/watch?v=swQTTG3NcYY
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Aug 2, 2009 18:52
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GWBBQ posted:Long shot here, but last winter or the winter before, one of the signs for CT-15 exit 35 southbound was demolished by something. I've been assuming a snowplow went off the road because I really don't know what else could have done that kind of damage. Do you have a record of it? Is the cost why it's not finished being replaced yet? Call up the maintenance division and tell them; it's possible that nobody noticed. Unfortunately, Connecticut doesn't have an electronic inventory of all of our signs. If we suspect a sign's missing, we have to look through plan sets dating back to the 1950s, project folders, and town filing cabinets to see if it's been modified since. The number is (203) 389-3010 for district 3 (the panhandle), or call my buddy Chris at (860) 594-2610 for statewide issues.
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Aug 2, 2009 18:53
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Silver Falcon posted:OP! Thank you for taking time to answer all our questions so far. This thread has been very informative. Now I'd like to add a question to the pile: AHAHAHAHAHAHA! AHHH AHHHAHAHAHA AHAHA.... Oh man... quote:Anyway, they have lots of nice straight streets set up in a grid system, and through the residential areas, to slow traffic down, they install the dreaded speed bump. My step-brother (before he was my step-brother), actually organized his boy scout troop to petition the town to install speed bumps on his street. My dad would curse his name every time we drove home. Seems to me such a thing serves to piss off the residents as much as it would slow traffic. Thoughts? Speed bumps are a horrible liability. In Providence several years ago, there was a raised crosswalk between the capitol building and the DOT. A trooper was responding to an emergency and drove up the hill well over the speed limit, hit the bump, and smashed down so hard that he broke his neck. You can bet there were some horrible lawsuits for that. Speed bumps are the bane of any emergency service. Go ahead and try to have one installed on your street, but when seconds count, I wouldn't want the ambulance to show up minutes later than it could. quote:On the other side of the coin, there was a certain side street that was very conveniently placed to avoid rush hour traffic on my way to school. Once, when driving that road, I noticed that the town had apparently either sold or given a portion of the road to one of the property owners, making a small spit of land stick out into the once-straight road, effectively making the road curve a bit. This in turn made traffic slow down out of the necessity of avoiding driving over the guy's lawn. This would seem to be a more effective way of slowing traffic down, and has the added benefit of not making it obvious that that's what's happening, so you don't piss off the motorists. It's a tricky situation because, on the one hand, sharp curves are great for slowing people down. On the other hand, they are a detriment to safety. We spend so much money REMOVING sharp curves, but I can certainly see how they'd be useful on residential streets. As long as the sight distance is good, the curve is obvious, and the right signs are up, I could get behind that. Other wonderful traffic calming solutions: people will generally drive as quickly as they feel is safe. That's why there's such a big correlation between speed and safety. However, there are ways to "trick" people into driving slower. One is by making the lanes narrower than they should be. The national standard is 12 foot lanes, but lower those by one or two foot, and people will really slow down. The extra space goes into the shoulders, which help offset the safety issues caused by people driving closer to the centerline. Another tactic is putting some light bushes along the edge of the road. The smaller the distance between the edge of the road and a perceived obstacle, the slower people will drive. If it's just a small bush, it won't really hurt a car if someone runs into it, but it will make people drive slower. Of course, they have to be well maintained, and shouldn't be used where pedestrians are present. Putting in a median can also help. It makes the lanes narrower, but at the same time, it all but prevents head-on collisions. A median also prevents mid-block left turns, which are a frequent source of accidents. Roundabouts are great for slowing traffic, especially a series of them every 1/4 mile or so. However, simply lowering speeds is not justification for putting in a bunch of roundabouts. Traffic calming should be seen as a benefit of using roundabouts, not a reason. quote:EDIT: Oh, and just to make it clear, I do not think that Phoenix is the paragon of urban planning, as the city claims to be. The place is a poo poo-hole, the very worst example of urban sprawl outside of L.A. The way the city is laid out makes it impossible to find your way around because every loving street corner looks the same. The city is run by idiots and I am so glad I don't live there anymore. Yes. Anyone who disagrees with this should take a look at the history of Phoenix's freeway network and their policy on growth.
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Aug 2, 2009 19:07
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My international intersection of the day: http://maps.google.com/maps?client=...014098&t=k&z=17  The fancy center road is toll, the outside lanes on the top and right are not, so they actually get more traffic than the toll road. Also, they managed to build a ring road, but don't have particular good connections to it from downtown BA.
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Aug 2, 2009 19:12
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Billy Maize posted:Just wanted to mention that drivers drive slower on narrow streets and even more so when there are cars parked on the side. The added benefit is a more pedestrian friendly area. Not only are speeds reduced but the cars parked along the street act as a buffer. That's not really true. We consider parked cars to be a hazard to pedestrians and bicyclists. Pedestrians crossing between parked cars are nearly invisible to traffic on the road, and cyclists can get knocked cold by doors opening. The best way to keep pedestrians safe is to make sure that they're visible. quote:I have a question about 45 degree angle parking (such as http://4.bp.blogspot.com/_RJ0lXJtyLoc/SGK2o6jkR4I/AAAAAAAAACc/6s9huHOvuCE/s400/angle%2Bparking.jpg). You can of course find this parking everywhere but more specifically I'm wondering about when it's in this sort of situation: http://maps.google.com/maps?f=q&sou...003484&t=h&z=19 This is a problem with all on-street parking, not just diagonal parking. Parking maneuvers are going to hold up traffic no matter what, except if you use parallel parking and have a lot of empty spaces. Motorists driving along on-street parking just have to expect that they may have to stop. For converting parking, back-in/head-out doesn't seem like it'd use any more space. Parking dimensions are a factor of angle, mainly, and not direction. I don't know of any parking up here that uses that method, but I'd like to try it out and see how it works.
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Aug 2, 2009 19:16
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Billy Maize posted:Ok this was easier to remember than I thought it would be. It's about Curitiba, Brazil. Looks pretty neat. I'll check it out of I ever get some free time. Maybe I can convince my bosses to play it at a training session, so I can even get paid for it!
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Aug 2, 2009 19:19
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smackfu posted:My international intersection of the day: Toll roads make a lot of special problems; I'm glad I don't have to deal with them. That interchange looks pretty efficient, actually, until you scroll to the East and see all the incredibly densely placed on- and off-ramps. I know it's a huge city, but does it really need ramps at every second cross road?
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Aug 2, 2009 19:21
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Cichlidae posted:This is a problem with all on-street parking, not just diagonal parking. Parking maneuvers are going to hold up traffic no matter what, except if you use parallel parking and have a lot of empty spaces. Motorists driving along on-street parking just have to expect that they may have to stop. For converting parking, back-in/head-out doesn't seem like it'd use any more space. Parking dimensions are a factor of angle, mainly, and not direction. I don't know of any parking up here that uses that method, but I'd like to try it out and see how it works. Overall its great, because it moves the trickiest part (backing up) to the visible part of the road. Its especially good for bikers, because when people pull out, they're facing forward and can see oncoming vehicles much easier.
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Aug 2, 2009 19:29
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Adding to the congestion model there is a OLD but very nice website from some german student of dresden university with a microsimulation of road traffic. You can adjust vehicle/h levels and on-ramp inflow on a highway inflow - also the percentage of truck/car traffic to see how a congestion starts and how the "shockwave" moves backwards. go play with it for a bit  http://vwisb7.vkw.tu-dresden.de/~treiber/MicroApplet/
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Aug 2, 2009 22:03
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skoops posted:Adding to the congestion model there is a OLD but very nice website from some german student of dresden university with a microsimulation of road traffic. You can adjust vehicle/h levels and on-ramp inflow on a highway inflow - also the percentage of truck/car traffic to see how a congestion starts and how the "shockwave" moves backwards. go play with it for a bit I'm convinced that Germans make the best traffic models. If you think that's cool, check out what Synchro and VISSIM can do. They make those applets look like child's play! Synchro:  Specializes in road networks, signalized intersections, and HCM (Highway Capacity Manual, another important book) calculations. Very simple to use. VISSIM:  Specializes in freeway, roundabout analysis, sophisticated driver models, and high-quality renders and simulations. Extremely flexible.
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Aug 2, 2009 22:28
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I am biased against roundabouts thanks to this one that I have to experience regularly. The only one I know of near where I live is this one, in the center of the city of Tallmadge, and it is a nightmare. All 8 of the main roads in town intersect in one big rear end circle, so there's basically no easy path to bypass it without going far out of your way. Not to mention there are 6-way intersections at each corner of the big "box" surrounding it. There is often such a long queue, especially in the north/south entrances, that you can easily wait in the queue for 5+ minutes just to reach the circle. I think it's supposed to be 2 lanes in the circle, but people drive it as if there's 1 lane. It's always full of traffic so you have to wait until there's an opening and then dart in. Do you think the problem comes from the outdated road planning (I think this circle was devised in the early 1800's) or people around here not knowing how to properly drive on a roundabout (i.e. using both lanes)? How would you fix it?
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Aug 2, 2009 23:22
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sm3g4 posted:I am biased against roundabouts thanks to this one that I have to experience regularly. The only one I know of near where I live is this one, in the center of the city of Tallmadge, and it is a nightmare. All 8 of the main roads in town intersect in one big rear end circle, so there's basically no easy path to bypass it without going far out of your way. Not to mention there are 6-way intersections at each corner of the big "box" surrounding it. That's not a roundabout, first off. It's a traffic circle. There are several differences between the two. Roundabouts are smaller, have narrower lanes, and wouldn't have 8 entrances. Traffic circles, on the other hand, aren't very useful. They're designed based on antiquated principles. When you have an intersection with 8 legs, that's just not kosher. The best way to fix it is turning it into a series of 4-leg intersections, like this:  You could put a modern roundabout at each of those three intersections if you wanted to maintain some remnant of the history of the place. My drawing's a bit rough; obviously you wouldn't want to pave over that church or whatever it is. This alternative is more context-sensitive: 
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Aug 2, 2009 23:47
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Great thread. Voted 5 and went hog wild. Anyway, I'm sorry if this has been mentioned, but up in Canada I've seen intersections that use a flashing green light when you have a protected left turn, and will switch to a solid green once the other direction gets a green or whatever. Maybe it's just me, but I thought that was fantastic. Green arrows are nice, but once I learned what it meant, I immediately wished we had that here in MA. Do you think that could ever work in America? (Or does it already somewhere in the US?)
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Aug 3, 2009 02:04
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Green arrows mean the same thing and are less confusing, so why?
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Aug 3, 2009 02:07
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