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Kaal posted:https://www.youtube.com/watch?v=YGLqnzSMc5g
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Sep 28, 2013 06:36
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Hedera Helix posted:What would it be called, in that instance? And at what sizes does a roundabout start being poorly designed? Or going in the other direction, at what size does it start being called a traffic island? Well the primary use case for a roundabout is for relatively low traffic circumstances, with somewhat balanced loads from all sides. Additionally, it should be constricting enough that traffic speeds throughout stay relatively low. Once you start having things like massive loads on only a few sides of it, or you're trying to push through enough traffic that having like 4 lanes in the roundabout is necessary, you've pretty much either outgrown or completely misimplemented the roundabout, and it should be replaced by something else. Often, this will take the form of punching through a more or less freeflowing path for the major road through the center, while retaining the rest of the circle format to handle movements into and out of the minor roads. Other times the situation will demand building a fully grade separated interchange, usually only when the two roads are both very heavily used.
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Sep 28, 2013 17:18
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Though I don't really have any questions, I'd just like to say I find traffic engineering and the like to be quite fascinating (though I don't know if I could ever make a job out of it). I often find myself analyzing the various traffic setups around town. And I don't mean just the lights, I mean the shapes of the roads and the frequencies at which traffic lights change and how engineers had to figure out how best to set everything up and analyze it over time to make traffic flow as smoothly as possible. It's really awesome and I just wanted to let the OP know that I ponder these things a lot while I drive. It's especially fun to think about these things where I live (Tallahassee), where the city planning is absolutely atrocious and confusingly abnormal.
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Sep 28, 2013 19:15
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http://connecticut.cbslocal.com/2013/09/19/champagne-spill-no-celebration-for-i-395-drivers/quote:It was a case of “the party’s over” before it even got started after an accident on Interstate 395 in Griswold, Connecticut, Wednesday. State Police say a tractor trailer carrying champagne hit a state DOT crash truck, spilling its cargo. edit: the Daily Mail, of all places, says the driver of the truck and the vehicle he hit were both treated for minor injuries at the scene, as was a man who walked up the hill by the crash for a closer look and quickly fell back down the hill. GWBBQ fucked around with this message at 10:11 on Sep 29, 2013 |
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Sep 29, 2013 10:03
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GWBBQ posted:http://connecticut.cbslocal.com/2013/09/19/champagne-spill-no-celebration-for-i-395-drivers/ Haha, I haven't heard anything about it, but I'm sure I'll find a mass email from the commissioner tomorrow. Those crash trucks are really something; they can deflect a semitrailer with only minor injuries for both parties. Or partiers, in this case. "I just wrecked millions of dollars of equipment! Let's break out the fancy glasses!"
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Sep 30, 2013 00:47
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Cichlidae posted:Those crash trucks are really something; they can deflect a semitrailer with only minor injuries for both parties. Link? I'm not sure I know what you're referring to. At least I can't picture it.
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Sep 30, 2013 04:33
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Yes, it's like a lava lamp.
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PittTheElder posted:Link? I'm not sure I know what you're referring to. At least I can't picture it. Various flavors of these badboys: https://www.google.com/search?q=truck%20mounted%20attenuator
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Sep 30, 2013 05:08
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I think it looks something like this: 
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Sep 30, 2013 05:08
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GWBBQ posted:edit: the Daily Mail, of all places, says the driver of the truck and the vehicle he hit were both treated for minor injuries at the scene, as was a man who walked up the hill by the crash for a closer look and quickly fell back down the hill. I want to believe the man climbing the hill fainted at the sight of the broken champagne bottles when he crested the hill.
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Sep 30, 2013 10:35
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We were in the Bay Area the last couple of weeks, and went over the fancy new Bay Bridge. One thing they have that I've never seen before is traffic lights on each lane, after the toll booths, that control the merges. They work like onramp lights, where one car goes for each green. It works well to reduce down from 15 or so toll booths to 5-6 travel lanes, but I don't understand why they didn't redesign the whole thing if they were spending billions on a new bridge. Automated high-speed tolling seems to be the obvious way of the future, and the Golden Gate bridge has already gone to it.
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Sep 30, 2013 17:12
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Just curious as to what you think of the new I-93 junction at the Rockingham Mall. I just drove from the mall southbound (towards 213) for the very first time last week and I have to say, as someone who really appreciates driving for what it is, the onramp that swings you right over the entire highway is beautiful. I tend to take Rt. 28 all the way to where it meets up with 213 but the other day I had a change of heart and decided to take the highway.
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Sep 30, 2013 20:42
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Modern Marvels was on the History Channel today, and I saw that the US apparently uses huge blocks of polystyrene foam as a stabilizer when the soil isn't firm enough to support a roadway (or as a support medium in bridges). Supposedly the foam blocks weigh ~2-3% of the equivalent volume of dirt and provide as much support for the asphalt and vehicles above. Who knows when this documentary was produced, but is this still true? Does it vary from state to state? Do other countries do this as well?
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Sep 30, 2013 21:44
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Grundulum posted:Modern Marvels was on the History Channel today, and I saw that the US apparently uses huge blocks of polystyrene foam as a stabilizer when the soil isn't firm enough to support a roadway (or as a support medium in bridges). Supposedly the foam blocks weigh ~2-3% of the equivalent volume of dirt and provide as much support for the asphalt and vehicles above. Wow, that's pretty wild: http://www.civil.utah.edu/~bartlett/Geofoam/EPS%20Geofoam%20Applications%20&%20Technical%20Data.pdf
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Sep 30, 2013 22:21
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That's pretty cool but how is it for the environment?? Also I want a small team of dudes to make a life size great pyramid model out of pyramid-block sized foam mega-bricks.
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Sep 30, 2013 22:25
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Devor posted:Various flavors of these badboys: Very cool. Definitely have never noticed one of those around here though. Baronjutter posted:That's pretty cool but how is it for the environment?? Probably fine? The big complaint about styrofoam and plastic is that they basically last forever, but if it's encased under a road, I don't see why that would be an issue. The real problem is what happens if they tear up the road and inevitably nobody will want to pay for cleanup, but that's hardly unique to this case.
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Sep 30, 2013 22:54
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There was talk about the Dutch approach to bicycles before in this thread. Well, The Boston Globe did a piece about that. Article with photos Video with some explanations by Dutch traffic folks. Please accept my humble apologies for the horrible English showcased by my fellow countrypeople. And they translated part of a bicycle theory exam 6th graders often take (no, it's not obligatory). You can try the exam here, if you like. However, it seems the Boston Globe folks lost a lot of subtleties here. Some of their answers are completely wrong except in some specific situations, and the picture are too small to see what's happening. There's also at least one case where the answer is not backed up by law, it's just the common interpretation of a certain situation. I could talk a bit more about that if you like, but I think there's other Dutch people following this thread who are better at pointing out errors than I am.
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Sep 30, 2013 23:48
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Yeah Q5 looks wrong to me since it should be a clear-cut case of 'rechtdoor gaat voor', plus it's a moped (snorfiets), not a scooter (bromfiets etc.), so it's allowed to be on the bikelane anyway. I don't believe there are any rules concerning rain, as Q8 seems to imply, rather, it's all about visibility conditions. Can't stand to watch the video, Dunglish 
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Oct 1, 2013 00:09
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Question: "This truck intends to turn right at the intersection. The moped rider intends to travel straight through the intersection. Who must yield the right of way?" Answer: "The moped rider must wait for the truck to turn right before crossing the intersection." Hmm, interesting. I forgot to rehost the picture and I'm getting paywalled, but I noticed the bikepath didn't extend further on the intersection. Is this why the truck had priority? Or the Boston Globe got that one wrong. We have this sign in Belgium:  Which I think means that you let the cyclist pass before making your turn. At least, that's what I always do. Also, as a Vlaming, I'll never not laugh at a Dutch person speaking English.
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Oct 1, 2013 00:21
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mamosodiumku posted:I think it looks something like this: We have special ones in Connecticut - they work super well, and are very easy to replace. Have a look. The champagne story didn't make the news here, at least from what I've seen, but there are pictures all over the web. FFStudios posted:Just curious as to what you think of the new I-93 junction at the Rockingham Mall. I just drove from the mall southbound (towards 213) for the very first time last week and I have to say, as someone who really appreciates driving for what it is, the onramp that swings you right over the entire highway is beautiful. Have a map for me? I try to avoid driving anywhere near Boston if I can help it. Grundulum posted:Modern Marvels was on the History Channel today, and I saw that the US apparently uses huge blocks of polystyrene foam as a stabilizer when the soil isn't firm enough to support a roadway (or as a support medium in bridges). Supposedly the foam blocks weigh ~2-3% of the equivalent volume of dirt and provide as much support for the asphalt and vehicles above. It is true. Rhode Island DOT used it on the Route 403 project, though, from what my professor said, it wasn't anchored well vs. sideslip and ended up with some crazy differential settlement. Structural foam's already in wide use for building construction, so it's only natural to use it for embankments as well. Fragrag posted:Also, as a Vlaming, I'll never not laugh at a Dutch person speaking English. Ahh, I miss Belgium so so badly. I'd love to live there someday, provided I can find a job. I can even make a decent half-assed attempt at Flemish.
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Oct 1, 2013 01:55
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Fragrag posted:Or the Boston Globe got that one wrong. We have this sign in Belgium: Well I'm sure they got the answer wrong. If anything the sign you posted is meant as a warning and only reinforces the rule right? (I'm not well versed in Belgian road law but I gather it's the same rechtdoor gaat voor stuff like here) Cichlidae posted:Ahh, I miss Belgium so so badly. I'd love to live there someday, provided I can find a job. I can even make a decent half-assed attempt at Flemish. I'd say come on over to the clog side but the big glut in infrastructure investment is receding.
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Oct 1, 2013 02:15
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Hi Cichlidae, I browsed through this entire thread over the course of what was probably a long time (didn't read every single post since a lot of them were Connecticut-specific and I wasn't interested in them). Anyway, just wanted to say that whenever someone brought up an interchange on the Parkway East in Pittsburgh back in 2011, and you said to change it to a simple trumpet interchange, well you can't. The parkway is set inside a narrow valley or gulley of some kind so there's no room to do anything, although it's not apparent from the satellite view. If someone asks you to do something about a Pittsburgh layout problem, the answer is No. Cause of the terrain. Nothing you can do, I'm sorry. Please fix us. We have so many folds in our poor city, we have no choice 
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Oct 1, 2013 03:13
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Grundulum posted:Modern Marvels was on the History Channel today, and I saw that the US apparently uses huge blocks of polystyrene foam as a stabilizer when the soil isn't firm enough to support a roadway (or as a support medium in bridges). Supposedly the foam blocks weigh ~2-3% of the equivalent volume of dirt and provide as much support for the asphalt and vehicles above. We use it in Canada too. Throw down a bunch of those blocks, cover it in dirt. Bam, overpass!
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Oct 1, 2013 07:01
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One other thing about the quiz is that the 'fietsstraat' has no basis in law. Those signs aren't even in the official road rules thing. Dutch link, check 'juridisch'. So I have no idea how they decide what the rules on these streets are other than by common interpretation. Apparently, Belgium does have a law about the bike streets.
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Oct 1, 2013 07:04
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quote:
Fragrag posted:I want to believe the man climbing the hill fainted at the sight of the broken champagne bottles when he crested the hill.
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Oct 1, 2013 17:42
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Cichlidae: I just stumbled across this http://jliszka.github.io/2013/10/01/how-traffic-actually-works.html What's your take?
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Oct 1, 2013 19:27
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Never letting anyone merge in front of you would be illegal, and an rear end in a top hat thing to do.
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Oct 1, 2013 20:05
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quote:there is a limit to the number of cars that can pass by a given point on the highway in a given amount of time, and that limit is one car every 2 seconds, per lane Not entirely true. While real-world gains are probably marginal, even the models we use locally take into account that there can be more than 0.5 vehicle per lane per second nowadays. People have adapted to heavier traffic conditions by driving closer to each other at the same speed here in the Netherlands.
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Oct 1, 2013 22:09
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Koesj posted:Not entirely true. While real-world gains are probably marginal, even the models we use locally take into account that there can be more than 0.5 vehicle per lane per second nowadays. People have adapted to heavier traffic conditions by driving closer to each other at the same speed here in the Netherlands. Isn't that where all these 50+ car pile ups come from? I always find my self driving at least 2-3x farther away than anyone else on the highway, and I think my distance is the absolute 2 second minimum. Anything shorter and you can't stop in time if the motorcycle in front of you slams on the breaks and beats you up.
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Oct 1, 2013 22:24
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Baronjutter posted:Isn't that where all these 50+ car pile ups come from? Our accident rate is pretty low as it is. I can't find anything else outside mortality figures at the moment but take a look at this graph: Persons killed per million inhabitants, 2008.  The US should be up there between Latvia and Slovenia with somewhat more than 100 fatalities per mio. IIRC. Anyway, I've seen enough cases in the Netherlands where 2150 vehicles (car equivalents) per hour was the basis for LOS calculations instead of the 1800 you'd get with 1 car per 2 seconds. That's a 20% paper increase in capacity right there.
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Oct 2, 2013 01:12
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Yad Rock posted:Hi Cichlidae, I browsed through this entire thread over the course of what was probably a long time (didn't read every single post since a lot of them were Connecticut-specific and I wasn't interested in them). Anyway, just wanted to say that whenever someone brought up an interchange on the Parkway East in Pittsburgh back in 2011, and you said to change it to a simple trumpet interchange, well you can't. The parkway is set inside a narrow valley or gulley of some kind so there's no room to do anything, although it's not apparent from the satellite view. That's why we invented dynamite, right?  ConfusedUs posted:Cichlidae: I just stumbled across this It's all absolutely factual, regardless of what judgments you might want to make. The whole impetus for ramp metering is to keep the freeway at LOS E (right at the tip of those flow graphs), because once it hits F, your capacity and throughput go down the drain. As for merging, think of it like you're all waiting in the security line at an airport. The line is split into two, but they all have to go through the same metal detector. Nothing you do is going to increase the number of people going through the detector, but you can decrease your wait in line by being pushy or choosing the shortest of the two lines. It's not very nice, but it works. Baronjutter posted:Never letting anyone merge in front of you would be illegal, and an rear end in a top hat thing to do. It's not illegal in and of itself; it's all about how you go about it. In stop-and-go traffic, if you stay glued to the car in front of you, there's nothing against the law about that. rear end in a top hat, though, I definitely agree. Koesj posted:Not entirely true. While real-world gains are probably marginal, even the models we use locally take into account that there can be more than 0.5 vehicle per lane per second nowadays. People have adapted to heavier traffic conditions by driving closer to each other at the same speed here in the Netherlands. He mentions a bit later that it's 1.5-2.0, but he rounds to 2 to make things simpler. Around here, saturation flow rate is 1850vphpl or so (1.95s/veh) for mixed traffic, and flow at LOS E is about 2300vphpl (1.57s/veh). It's significantly lower in rural areas and significantly higher in urban; around Boston or New York, the flows probably approach 3000vphpl for passenger cars. Baronjutter posted:Isn't that where all these 50+ car pile ups come from? I always find my self driving at least 2-3x farther away than anyone else on the highway, and I think my distance is the absolute 2 second minimum. Anything shorter and you can't stop in time if the motorcycle in front of you slams on the breaks and beats you up. Leaving a gap won't work in New England: someone is guaranteed to merge right in front of you. If the gap is more than about 2.5 seconds, it's not going to be a gap for long. In that case, you're forced to go much slower than prevailing traffic to maintain a gap, and you're going to get nastily rear-ended. Koesj posted:Our accident rate is pretty low as it is. I can't find anything else outside mortality figures at the moment but take a look at this graph: Fatalities per million inhabitants isn't a very good metric. The results are artificially low for countries with low car ownership or low vehicle miles per person (Malta, for example.) Fatalities per million registered drivers is slightly better. Fatalities per hundred million vehicle miles is much better.
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Oct 2, 2013 02:21
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Ah okay I missed the part where he put some more nuance to his figures, guess I was too quick to nitpick. You're also right about the accident metrics of course. But wow possibly up to 3000vphpl, even if it's just a ballpark guess it's something I hadn't heard before.
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Oct 2, 2013 03:41
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Cichlidae posted:Have a map for me? I try to avoid driving anywhere near Boston if I can help it. Surprise, this is near Salem, NH.  The map doesn't really do it justice as to the way it looks in person.
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Oct 2, 2013 20:42
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What is it about road projects that makes them take years and years on end? Are they technically demanding, in terms of construction, are they operationally difficult, because you have to keep what you're working on simultaneously open, or are they just corrupt to the bone, with six hour workweeks? Also; do you have a variable in traffic studies for braindead idiots who can't be asked to do anything but hit their hazard lights and panic when it starts to rain? I ask because Miami just robbed me of an hour and a half of my life to go twenty two miles, twenty of which are on highways...
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Oct 2, 2013 22:18
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I just drove by it this weekend (the I-93 thing), it really is impressive, for a directional wye. But they're doing a lot more work on 93 in that area. Are we finally going to have six lanes up to Derry?
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Oct 2, 2013 22:55
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MrYenko posted:What is it about road projects that makes them take years and years on end? Are they technically demanding, in terms of construction, are they operationally difficult, because you have to keep what you're working on simultaneously open, or are they just corrupt to the bone, with six hour workweeks? Having worked next some road crews: building a road is tough, and slow going. You've gotta cut down to subgrade and get that dirt out of there. Then you bring dirt back in to get your subgrade. Compact and level that. Get it inspected. Then bring in your base course. Compact and level that. Get that inspected, as well. Then your base pavement layer, then finish pavement layer. Once that's done, you have to do all the other stuff that facilitates using the pavement: lines, signs, reflectors, posts, curbs, edging, grooving, etc. And it just takes a long time. Compacting machines move at (if you're lucky) 1mph. So you could completely compact 8 miles of one lane in a day. That goes for pretty much any of the machines out there. The pavement machines drop down about 75% of a lane of pavement, and move at a slow walk. So if you've got three lanes of pavement and one machine, you're making four or five passes. How long would it take you to walk 80 miles at the same speed you'd use to sweep a floor? That's AFTER everything else is done. This doesn't even take into account the earthworks before the grading of the road. Or overpasses/bridges/culverts. Road crews aren't lazy; roads aren't simple.
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Oct 2, 2013 23:29
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babyeatingpsychopath posted:Having worked next some road crews: building a road is tough, and slow going. You've gotta cut down to subgrade and get that dirt out of there. Then you bring dirt back in to get your subgrade. Compact and level that. Get it inspected. Then bring in your base course. Compact and level that. Get that inspected, as well. Then your base pavement layer, then finish pavement layer. Once that's done, you have to do all the other stuff that facilitates using the pavement: lines, signs, reflectors, posts, curbs, edging, grooving, etc. Good answer. Also worth noting that with unlimited manpower and lots of machines you could get it done pretty fast but contracting companies can't really hire thousands of skilled workers for a week and them dump them, and you still might have to wait for ground to settle, various engineering items to be manufactured (E.G. Bridge beams, barriers) inevitable delivery delays, etc. Timing of construction works is run on Critical path method which in a nutshell consists of "work out the vital things that have to be done in order (The critical path), then arrange the items that can be done at any time around that." This then forms the basis for how many workers, machinery, etc, is required. (I'm not totally up on how it works in practice) E: Gantt Charts are a cool way of seeing the critical path. One of the recent projects I worked on had one that covered three-quarters of a Portacom office wall. Jaguars! fucked around with this message at 01:27 on Oct 3, 2013 |
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Oct 3, 2013 01:16
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That ties into something I've wondered about before: how much does the local area's ability to produce asphalt and concrete affect the time you can build stuff in?
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Oct 3, 2013 03:35
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dupersaurus posted:That ties into something I've wondered about before: how much does the local area's ability to produce asphalt and concrete affect the time you can build stuff in? I thought you could transport concrete quite far with those mixer trucks, but Wikipedia says that even when it's constantly stirred, it has to be used in 90 minutes. Those things aren't too fast, so a max radius of perhaps 100 - 150 km from the plant? So you need a plant for every 200 km wide area, which isn't a problem for urban areas, but I can see that being a problem for the really rural parts. I guess you could always just mix the cement powder and water on the spot if you need to, that would remove any distance limits on transport.
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Oct 3, 2013 06:41
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Carbon dioxide posted:I guess you could always just mix the cement powder and water on the spot if you need to, that would remove any distance limits on transport. Yeah, but I don't think you want to do that for any larger projects like road construction. I was once at a party with a man whose line of business was building cement factories in developing countries. You'd be amazed at how much money is to be made in that, but the challenge seemed to be to get permits from the local government, because it has some environmental impact. Apparently, he'd become quite expert at bribery.
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Oct 3, 2013 12:03
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Carbon dioxide posted:I thought you could transport concrete quite far with those mixer trucks, but Wikipedia says that even when it's constantly stirred, it has to be used in 90 minutes. Those things aren't too fast, so a max radius of perhaps 100 - 150 km from the plant? So you need a plant for every 200 km wide area, which isn't a problem for urban areas, but I can see that being a problem for the really rural parts. For big jobs:   For small: 
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Oct 3, 2013 12:48
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