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Golbez posted:Despite remembering the days of DPPH, that is somehow the sexiest post in the forums. Agreed. (Yeah, I'm an 05, but I've been lurking for a decade and a half).
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Apr 28, 2016 21:27
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Devor posted:As a bit of an aside, Shop Drawings are how the engineering documents get turned into a diagram for how the contractor plans to actually build something. We might call out a simple prefabricated pedestrian truss bridge, that is essentially a big 12'x8' rectangle, 100 feet long. We don't particularly care exactly what size the members are, we don't care where the contractor puts his splices, etc, so we don't even specify those on the plans. We let the contractor (or the bridge manufacturer that he's buying from) tell us what they want to build, and we check the calculations. We use shop drawings in traffic engineering as well. Overhead sign supports, for example, are designed in a relatively vague way, and the contractor is expected to produce their own design and submit it for review. This is a relatively recent (~5 years) change intended to save cost. The DOT's previous design required hot-dip galvanizing which could only be done in a single factory in Utah or something, so each support cost ~$250,000. By letting the contractor design it, the cost is more like $80,000. Is it as durable? Probably not, since it's the same type of sign support we used in the 1970s and found lacking. I suppose you'd have to look at the benefit:cost comparison of signs that are 3x cheaper versus a chance of one or two occasionally falling and crushing a car. A fatality might cost the state $10M or so. You can save that in a single project by using cheaper sign supports. Is it ethical? Don't know. We'll have to figure that out when the first of the new sign supports fails. Temporary traffic signals are another thing the contractor designs. I've never seen a shop drawing for one, though. We specify the signal head locations and the phasing, and the contractor just makes it happen. Sometimes they use old mechanical signal controllers from the 1950s. I still expect to drive through a work zone sometime and see old incandescent lights instead of the LEDs we've been using for two decades now.
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May 3, 2016 12:31
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Carbon dioxide posted:Tonight a part of the Dutch A1 highway is closing down. The reason is that they built a new train bridge that has to go over the highway (that's being widened, so the old rail bridge doesn't fit anymore), but they built that thing to the side so they didn't have to close down the highway for weeks. Is Mammoet doing it? They brought their SPMTs over to Rhode Island when I worked there to move the Providence River Bridge. I was lucky enough to see the bridge in construction before it was moved, and then watch it on the traffic cameras the morning of the float as it came up the bay.
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May 6, 2016 21:27
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The latest traffic volume trends are in. Here is the nationwide graph: Yup, we're making up for lost time. The reason for that little missing chunk from 2008-2014 is debated, but the general consensus seems to be its cause was the recession. The very fast growth since, rivaling what we saw in the 1990s, reflects an economy that's picking up steam once more. Of course, these gains aren't nationwide. But unlike what you might expect, volumes on the East Coast are growing faster than the rest of the country. New England, for example, gained 6.1% year-on-year. Connecticut, where there hasn't been a significant increase in lane-mileage for 20 years, saw a 5.8% increase in volumes this past year. That's huge. That's a 12-year doubling rate. You might wonder how it's possible for roads that are congested for several hours a day to take more traffic. Well, I've got two theories. The first one is the pessimistic one: the congestion spreads to off-peak hours as people adjust their commutes. If I had the time to look through the detailed hourly data, I could see if that's the case. The optimistic theory is a bit nicer: roads operate most efficiently at Level of Service E. A road at LOS F is moving fewer cars than one that is less congested. So if the demand goes down, paradoxically, you could end up with a higher throughput. Traffic engineering is weird. If you've been reading for a long time, you might remember that the main selling point for the Busway was how much traffic it would take off I-84 between New Britain and Hartford. Well, it turns out there's a continuous count station in West Hartford just west of Hartford, and it just churned out its March volumes, so I took a gander at how the counts have changed in the year since the Busway opened. Drum roll please: 5.3-5.9% increase in traffic, depending on how you measure it. Ouch. Cichlidae fucked around with this message at 02:48 on May 10, 2016 |
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May 10, 2016 02:40
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Jeoh posted:London's CYCLING SUPERHIGHWAY is getting some pretty good usage: https://www.youtube.com/watch?v=QLCm2hoM9aE Just curious, what separates this from a typical buffered cycle track? Is there some special feature I'm not noticing?
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May 10, 2016 22:22
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It needs to have retroreflective white bars or stringers in order to be a valid crosswalk. I don't know if those outlines are going to pass the test.
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May 13, 2016 04:21
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Baronjutter posted:All the cars need is their stop bar and the lights. They could replace the whole thing with dark gray cursive that says "this is not a crosswalk" and it wouldn't change anything. Stop at the stop bar on a red light, easy. I know drivers have a hard time with just about everything but I think they can manage that. It's not like they're stop extra hard on a red if there's a regulation striped crosswalk. That depends on whether the state has a vulnerable users bill. In some states (CT included), if a car hits a ped, it makes no difference whether the ped was in a crosswalk or not. In a state without one, if the light is green and a ped steps off the curb and gets creamed, what happens next depends on whether there's a marked crosswalk. Regardless, I think there is a definite safety bonus to having those retroreflective white lines. With bars or stringers, you can see a pedestrian wearing black even in the dead of night because they stand out against the bright retroflective paint. So even though yeah, crosswalks at intersections don't serve a legal function here, I will still design every single one of them to meet the MUTCD requirements, even if it clashes with the aesthetic.
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May 14, 2016 15:03
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John Dough posted:Would the bars still serve a legal function if the lights are out for whatever reason? Absolutely. Since they're retroreflective, a car's headlights are all that's needed to make them visible. On the other hand, if you're just using white paint without the beads, then it's practically invisible at night and there is probably a case of gross negligence going on.
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May 15, 2016 04:50
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Baronjutter posted:All the road markings here turn 100% invisible if it's dark and slightly rainy. Some areas have fancy glowy paint but for the most part you just have to remember how the roads work. Retroreflective beads last somewhere from 1-6 years depending on ADT. If you're in a place without plows, they might last longer. Since we started embedding the markings in grooves, they've been lasting much longer and becoming more visible in bad weather. Signs, too, tend to wear out after a little while, 10 years or so. Certain colors wear much faster than others. Red, I've noticed, fades VERY quickly and I'm not sure why. There are other relatively low-cost technologies to maintain retroreflectivity, especially in inclement weather, but ConnDOT in particular has an aversion to them. That will probably change in the next few years. However, we don't have the money to pay for this stuff. On state roads, signs and markings typically get replaced after they've been through 2-3 lifetimes. On local roads, they might only get replaced when there's a bad accident or when someone complains. The benefit to keeping them bright outweighs the cost of installing them, but you know how the US is about investing in infrastructure. If you asked the NCUCTD (the group that makes the MUTCD), they would probably say that pavement markings or signs that are no longer retroreflective are no longer traffic control devices. And at that point, you have an uncontrolled road. Some signs we could definitely live without, but centerlines, lane lines, and edge lines are crucial. So the short answer to a question you didn't really ask is, yes, the existing conditions aren't to spec. That doesn't mean we should keep neglecting our infrastructure, it means we should try harder.
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May 15, 2016 13:54
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Devor posted:Unit Block is apparently a weird DC thing? I thought everywhere had Unit blocks. Instead of the 0-block, which sounds weird, they call it the Unit Block Block numbering is a strange and foreign concept to those of us in New England.
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May 18, 2016 04:06
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My Imaginary GF posted:I give a gently caress about individuals who are most likely to make money for business owners and generate sales taxes, of which pedestrians generate a higher quantity. Why the gently caress don't more folk care about the gently caress'n money in a sustainable and environmentally friendly manner? Here's where the math gets involved. I made an effortpost months ago about balancing safety vs. efficiency. If we only care about efficiency, we build infinitely wide roads with no speed limits. If we only care about safety, we lock people in their houses. In the real world, we strive to strike a balance, and the simple truth is that there is no one road layout that fits every situation. In a spread-out suburban area that's not accessible to pedestrians, there's no point to having a 20-foot-sidewalk and cramming a 40,000 ADT into two lanes. 99.99% of your traffic is going to be vehicular. With great bike and ped facilities, you might push that down to 99.90%. On the other hand, in an urban area with high density and a grid-based redundant street network, changing the road configuration might change it from 80% to 50% without too much hassle. It's all situation dependent. Now for two pet peeves of mine: First, pedestrians aren't the only group of travelers who have fatalities. A pedestrian life is not inherently worth more or less than someone on a motorcycle or driving a semitrailer or riding a horse. Right now, in the last year or two, fatality rates for motorists have been skyrocketing. I'm not sure about peds and bikes; latest data I saw showed a steady decrease, but that was just for one state. We have serious systemic safety concerns, and just throwing money at one group of users isn't going to make the system as a whole any safer. When you consider that there's limited funding available for this stuff (another chagrin of mine), you can probably understand why a DOT would rather spend $50,000 putting centerline rumble strips on 50 miles of a busy road and save a life or two every year than redoing the road network downtown for $10 million for a similar fatality reduction. Second, the word "sustainable" is meaningless. Transportation is inherently unsustainable. Human life is inherently unsustainable. It's just an awful word all around. You can consider degrees of sustainability, I suppose, but saying one thing is sustainable and another is not is incorrect. ----- I am putting this in a separate section because it's tangentially related but I have no idea whether it's true or not. Hopefully someone in the thread has done research on it and can share some real data. There is an assumption that any kind of self-propelled vehicle is going to be less environmentally friendly than walking or biking. But humans emit CO2 as well. I used to think that it was really stupid to consider the CO2 humans emit when under exertion, but someone said in another thread that bicyclists emit about 90g/km of CO2 above the normal human resting metabolic rate. This is compared to something like ~120g/km of CO2 for a passenger car. So if those numbers are correct, overall CO2 emissions would be lower if you carpooled than if you rode a bike. The poster didn't cite any numbers for walking or jogging, but they did mention that mass transit was much, much lower in CO2 emission. Two big assumptions here: one is that it only counts the fuel the car burns, not the resources used to make it or to build facilities for it. I guess if you bought your car used, that would be less of an issue. We'd also have to consider the bicyclist - if they're eating imported foie gras and drinking triple-distilled Tibetan spring water, those calories they're burning will have a much higher footprint than just the CO2 emitted through metabolism. The second big assumption is that the car is burning gasoline. Ironically, considering the power grid here in New England is mostly coal and oil, an electric car would produce more emissions than a gas-burning car. But in places with cleaner power grids, we could cut that 120 g/km significantly with electric vehicles. I get the feeling you need a doctorate to make an informed decision about this stuff. Has anyone done a proper cradle-to-the-grave environmental impact analysis of the various modes of transportation? Edit: Math Cichlidae fucked around with this message at 02:50 on May 19, 2016 |
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May 19, 2016 02:46
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Javid posted:Doesn't car exhaust puke out a significant number of unpleasant chemicals, not just co2? That'd certainly be one important factor. Yeah, absolutely. The post I read only mentioned CO2. We'd have to look at NOx, CO, and particulates as well. Hope your populace doesn't drive a lot of Volkswagens... Edit: That's another subject that deserves a discussion of nuance. As part of the NEPA process, we look at the total emissions footprint of a road network for the build alternative versus the no-build. In order to protect the health of the people who live in the project area, a major objective is to improve air quality, and if you can't improve air quality vs. the no-build, that's going to be judged very harshly. In our project, I'll almost certainly be fighting that. My procedure was to keep intersection size at an absolute minimum, so long as they don't back up onto the freeway. As a result, the overall LOS gets worse vs. the no-build, and emissions are significantly higher. That's going to be a tough sell to the EPA. But I'm willing to fight that fight. I don't want people to get the impression I'm all, "hrr peds bad, cars good." This project is in a small urban area (120k people) and its density is sufficient that it's well worth removing some traffic lanes to add bike facilities and wider sidewalks. VVVVV Haha don't mention the obesity thing on Tumblr. More and more, it seems like being obese is the favored state in the US. Cichlidae fucked around with this message at 03:16 on May 19, 2016 |
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May 19, 2016 03:04
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Alkydere posted:As a former pizza delivery driver...the idea of a city without block numbers terrifies me. In the days before conveniently having maps on my phone I was able to easily figure out where a house was within seconds once I knew the block # and where the street was. Not to mention if it was on the north/south, east/west side depending on if it was an odd or even number. My street always confused pizza delivery drivers: the houses went 32, 34, 40, 38, 36. We had the house number on our mailbox and front door, but we still had pizza deliveries getting lost maybe a third of the time. We kids eventually learned to just sit out on the curb and wait for them. Skeesix posted:Something seems very off here, maybe even order-of-magnitude off. Let's say we have a small, very fuel-efficient car with only an internal combustion engine so let's say it gets say 40 miles per gallon. Gasoline is just refined hydrocarbon and the car does a good job of converting that plus air into Water, Nitrogen, and CO2. A gallon of gas contains roughly 30000 calories worth of energy - and the CO2 produced over that 40 miles should be roughly proportional to the energy converted. Thanks, I'll question that guy if he makes the same assertion again.
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May 19, 2016 12:11
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Golbez posted:Why? The houses were built decades apart by high school students and the parcels were subdivided. Cicero posted:This isn't really true. In particular, sprawly suburban development that focuses on cars above all else tends to be literally unsustainable, because it acts as a ponzi scheme. It doesn't have to be unsustainable; you could make it sustainable by raising property taxes enough to pay for infrastructure maintenance/replacement, and sometimes that ends up happening if the economy is good and property values rise. But it can certainly be unsustainable, there are some case studies linked to here: http://www.strongtowns.org/journal/2011/6/14/the-growth-ponzi-scheme-part-2.html What about development in general, any kind of development, is sustainable? Any growth rate, even 0.01%, is unsustainable. Even if you're not designing for cars, even if you're just building sidewalks and 3-story brick buildings, that concrete requires aggregate shipped from far away, Portland cement shipped from far away, maybe fly ash or petroleum-based admixtures. Bricks require digging up something's ecosystem and baking it (maybe in the sun, if you're lucky, but otherwise in a furnace), then mortar, which is just concrete without aggregate. You're using metal, which is unsustainably mined and smelted, you need farming, which isn't great for the environment no matter how you do it (especially if you need to support 10+ billion people), you need some way to ship freight long distances. It probably uses much less energy and resources than roads do, but it's not clean. I mean hell, if you want to go for the ultimate proof, entropy must always increase in a closed system. So unless we find a way to create a new sun out of nothing, we are all inevitably using up finite resources. I think it's fair to say one thing is MORE sustainable than another, though. Just not that something is straight-up "sustainable." Nothing is. (Like I noted, it's a pedantic argument.) Cichlidae fucked around with this message at 12:43 on May 20, 2016 |
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May 20, 2016 12:09
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