|
 SIGNAL WARRANTSor: How the Mayor Signalized his Driveway There are 760 pages in the current version of the MUTCD, divided into 10 chapters. Most people, however, have only read 9 pages of it: Chapter 4C, the guidelines to determine when an intersection should be signalized. It's a list of 8 warrants, any of which is grounds to install a traffic signal. As you might expect, the most popular part of the Manual is also the most abused and misunderstood. "But Cichlidae," you'd begin, "this is a federal document used and trusted across the country! Surely it's all based on tons of scientific studies and decades of experience!" I'd respond... well, I'd be too busy cackling, really, but once I'd caught my breath, we could have a nice long talk about how the MUTCD was made. The truth is, most of the MUTCD is pretty sound. Sure, it changes from decade to decade, but that's all thanks to lots and lots of research. For a traffic engineer like me, it's an excellent and reliable resource. For a politician, however, only Chapter 4C matters, and there's one glaring problem with that: Chapter 4C is optional. That's right! Your intersection could meet all 8 warrants, and you don't need to build a signal. Heck, it could meet none of the warrants, and still be signalized. The warrants are not rules, they're not even guidelines! They're guesses. Warrant 1 Back in the 1930s, during the Great Depression, President Roosevelt initiated a huge amount of federal spending on infrastructure including dams, sewers, and roads. Chicago, being a big city, got a big bunch of cash, and decided to use it to put newfangled traffic signals in their city streets. They made a list of all their intersections, ranked them by volume, and went town the list putting in signals until they ran out of money. A few years later, the FHWA started writing the first MUTCD, and asked what criteria should be used to signalize intersections. Chicago mentioned their method, and the MUTCD guys thought it was such a good idea that they adopted it. That's how we got Warrant 1.  Warrant 1 is the 8-hour volume warrant. If your roads have a higher volume than the Chicago cutoff, 500 cars on the main road and 150 for one direction of the side street, for 8 hours per day, you might want to consider possibly thinking about a signal. Well, that wasn't enough for some people, because intersections often have multiple lanes! The committee got together and decided on a few numbers for multi-lane approaches. Again, this wasn't science, this was compromise. Well, turns out that wasn't enough, because some of the more rural areas wanted to put signals in low-volume places. Some more deliberation took place, and the next MUTCD gave a 70% reduction factor for rural areas. Of course, wanting to take advantage of this, they also defined "rural" as a road with a speed exceeding 40 mph. Design speed? Posted speed? 85th %ile speed? Depends on whether or not you want a signal  This still wasn't enough flexibility for some folks, so the FHWA added a new warrant (now Warrant 1B): if the volume on the main street is really high, then you can signalize at lower-volume side streets. Cool, huh? Still not enough? You betcha. Finally, the FHWA decided that intersections that come close to meeting both warrants 1A and 1B, but not quite making it, could be signalized. They just have to meet 80% of both warrants (or 56% in rural areas). If you're not confused yet, there are still 7 more warrants to go. Warrant 2 What if your road doesn't have high enough volumes for all 8 hours, but you still really really want that signal? Fear not! Texas brings us Warrant 2, the 4-Hour Vehicular Volume Warrant. You just take your 24 hourly volumes and plot them on the graph below. If any 4 of those points are above the appropriate line, you can signalize.  "Wait a minute," you shout, "those are graphs! That means science!" That's not science you're seeing; it's Texas' idea of what ought to make a good signal, drawn with a French curve. Of course, that graph has a counterpart with all of the volumes reduced to 70% for use in rural areas. Warrant 3 Wait, that's still not enough to get the DOT to install that signal you want so badly? Well, Warrant 3 is here to help. You only have to have "undue delay" for 1 hour out of the day! Does that graph look familiar? Yep. I bet you can guess where it came from.  I have to admit, there is one bit of science in Warrant 3, and that's in the alternative warrant: instead of using the graph, you can signalize if the side street has at least 4 or 5 vehicle-hours of delay and meets a couple volume warrants. Warrant 4 Still can't get that signal installed at the end of the mayor's driveway? Cheer up, maybe the Pedestrian Volume Warrant will work! If you have at least 100 peds in each of 4 hours, or 190 in 1 hour (throw a yard sale while the engineers are doing ped counts), and there are fewer than 60 gaps in vehicular traffic per hour, you can signalize. You can't use the warrant, however, if there's another signal within 300 feet. Where do we get these numbers? Well, get me some latex gloves and some Astroglide and I'll show you. Warrant 5 School Crossing! That'll do it for sure. Got school kids? At least 20 in one hour? No signal within 300 feet? Bingo. Arrange a field trip at your house, and you've got 20 kids. There's no way anyone would oppose a signal for our kids' safety, right? Warrant 6 Coordinated Signal System, AKA "The Mayor's Friend." This is an incredibly vague warrant, and that often leads to abuse. The only number involved is the 300' minimum distance to the next signal. Behold: "On a two-way street, adjacent traffic control signals do not provide the necessary degree of platooning and the proposed and adjacent traffic control signals will collectively provide a progressive operation." What's a progressive operation? Whatever the politician in charge says it is. Yay! Warrant 7 Well, somehow you screwed up and couldn't meet Warrant 6. We'll give you another chance. If you came pretty close to meeting the volume warrants and there have been at least 5 preventable accidents here, and Warrant 8 This is it, your last chance to make a dent in the traffic stream. Let's get super vague! Just pick one criterion from each list: 1) You think it'll meet one of the warrants in 5 years. (Sure, I promise!) 2) Traffic's high for 5 hours on a Saturday or Sunday. 1) It's an important road. 2) It includes rural or suburban highways outside, entering, or traversing a city (not kidding at all here) 3) It appears as a major route on an official plan. (Jackpot!)  ----- Well, I hope you've learned something about the MUTCD. Furthermore, the next time someone takes the warrants seriously, you can give them a very logical middle finger. As the MUTCD itself says, The satisfaction of a traffic signal warrant or warrants shall not in itself require the installation of a traffic control signal. The only way to find out for sure if one is needed is to do an engineering study! Disclaimer: A lot of this information came from Rick at Iteris, who taught my signal design class. That's as close to citing sources as I can get, unfortunately. Also, I'm not saying that the MUTCD is wrong or shouldn't be trusted. It is just very easy to misinterpret. Cichlidae fucked around with this message at 02:33 on Oct 28, 2009 |
#
?
Oct 28, 2009 02:20
|
|
|
|
| # ? May 17, 2024 18:30 |
|
|
http://maps.google.com/?ie=UTF8&ll=41.050525,-73.534756&spn=0.001452,0.00284&t=k&z=19 The exit ramp is blind to traffic coming up from behind on the right until between the first and second dashes after the solid line. In your professional opinion, should it be legal to kill or maim drivers who exit the ramp and immediately make a blind triple lane change to turn right instead of taking the exit half a mile back that safely puts you into one of those lanes? Cichlidae posted:Sea travelNiemand weiß was die Zukunft bringt, but I'm betting on ships that take advantage of ground effect, more efficient engines, and hopefully some new/bigger canals to facilitate things. Winter Light posted:What's up with Connecticut's plow whenever/ocassionally sand/never salt policy? Cichlidae posted:There are some more exotic interchanges that would work out, but it's tough to settle on one without the volumes on hand. Both roads are at-grade arterials, not freeways, and they shouldn't need a gigantic interchange; a well designed partial cloverleaf could push through nearly as much traffic as the existing cloverleaf. If the turning volumes are relatively small, then let's do something awesome and build this: 
|
|
#
?
Oct 28, 2009 19:05
|
|
|
Cichlidae posted:So they made you put in a signal so the mayor could get to Hooters that much faster? We can't be delaying the mayor in such an important endeavour. Mayor's got to get some titties in his face and it needs to be that way now! No seriously, I love your graphics.
|
|
#
?
Oct 28, 2009 19:18
|
|
|
Vanagoon posted:So they made you put in a signal so the mayor could get to Hooters that much faster? We can't be delaying the mayor in such an important endeavour. Mayor's got to get some titties in his face and it needs to be that way now! I saw this as a policy map being drawn on a Hooters napkin, which makes it that much funnier. Great explanation of signal warrants. I had no idea those graphs weren't based on seconds of delay or anything actually engineering-related, but it makes sense.
|
|
#
?
Oct 28, 2009 19:36
|
|
|
GWBBQ posted:http://maps.google.com/?ie=UTF8&ll=41.050525,-73.534756&spn=0.001452,0.00284&t=k&z=19 In my professional opinion, we should raze everything within a block of 95 and build it properly to begin with. No laws or signs can make up for bad geometrics. quote:Unfortunately, the world's largest cargo ships each emit as much carbon and particulate pollution per mile as 70 million cars. The only alternatives are to filter/sequester emissions or pump it all into the water, which creates an entirely different environmental nightmare. Burning fossil fuels to move cargo needs to be reduced or eliminated, possibly with carbon neutral biofuels, but on a large scale we need something more sustainable *cough* nuclear *cough* Hey, I'd love to switch over to nuclear, and a big part of the reason I chose to work in France instead of Germany is because of their success in that field. All the same, how's that going to help us move cargo across oceans? You'd need a tremendous battery to hold enough energy for a trans-oceanic trip. Maybe you could use electrolysis to get a lot of compressed Hydrogen or a similar scheme, but that would hurt efficiency (and, therefore, the bottom line.) quote:Sand washing into rivers and wetlands was really loving with wildlife, including protected species. Surprisingly, salting is a lot more innocuous, plus it turns our roads an awesome whitish grey and doesn't require street sweeping in spring. Oh jeez, I have such an awesome story about that, but I can't tell it without getting sued or worse  quote:Let's elevate or drop the ring to whatever height it needs to be since it needs to be grade separated from the highways anyway, and have the ramps go under it and join up with the inside of the ring as indicated in my crappy MS Paint edition (yes, those are supposed to be connected to the ring.) If I'm visualizing it right, this would require no weaving as opposed to the original having people exiting the ring have to cross the paths of people entering the ring. That would add a lot of cost to the project; you'd be better off just making it a turbine interchange in that case. Weaving issues on the circular roadway wouldn't be all that bad due to the lower speed and the fact that only left-turning traffic needs to merge left and back right.Plus, the weave distance is greater than that provided between the existing loop ramps on the main line.
|
|
#
?
Oct 28, 2009 21:23
|
|
|
Vanagoon posted:So they made you put in a signal so the mayor could get to Hooters that much faster? We can't be delaying the mayor in such an important endeavour. Mayor's got to get some titties in his face and it needs to be that way now! The intent was to have the "Official Map" drawn in marker on a cocktail napkin. I should have made the texture effect a little darker, sorry  Yeah, like this: Dominus Vobiscum posted:I saw this as a policy map being drawn on a Hooters napkin, which makes it that much funnier. I'm glad it was informative! Hopefully you understand how frustrating it can be when someone treats the signal warrants as some infallible message from God. "What do you mean you can't put in a signal? IT MET THREE WARRANTS!"
|
|
#
?
Oct 28, 2009 21:26
|
|
|
GWBBQ posted:Unfortunately, the world's largest cargo ships each emit as much carbon and particulate pollution per mile as 70 million cars. My source says 50 million cars: International: One ship equals 50m cars: study shows pollution toll The Guardian (London) - Final Edition, April 10, 2009 Friday, GUARDIAN INTERNATIONAL PAGES; Pg. 24, 741 words, John Vidal, Environment editor http://www.guardian.co.uk/environment/2009/apr/09/shipping-pollution "Britain and other European governments have been accused of underestimating the health risks from shipping pollution following research which shows that one giant container ship can emit almost the same amount of cancer and asthma-causing chemicals as 50m cars." Do you have another source that I may have missed? Either number, that's an amazing amount of pollution.
|
|
#
?
Oct 28, 2009 23:40
|
|
|
Cichlidae posted:All the same, how's that going to help us move cargo across oceans? You'd need a tremendous battery to hold enough energy for a trans-oceanic trip. Maybe you could use electrolysis to get a lot of compressed Hydrogen or a similar scheme, but that would hurt efficiency (and, therefore, the bottom line.) Put a nuclear reactor on the ship, just as some submarines and aircraft carriers already have. Pretty much unlimited range without a refill. Great thread. Did you ever play Transport Tycoon? Building complicated railway junctions on that is particularly rewarding. Would definitely play the poo poo out of a road-based equivalent.
|
|
#
?
Oct 29, 2009 00:36
|
|
|
mike_F_ posted:Put a nuclear reactor on the ship, just as some submarines and aircraft carriers already have. Pretty much unlimited range without a refill. Oh duh, that would work excellently. One company (Toshiba I think?) is even producing fridge-sized nuclear units that could easily provide power for smaller ships. quote:Great thread. Did you ever play Transport Tycoon? Building complicated railway junctions on that is particularly rewarding. Would definitely play the poo poo out of a road-based equivalent. I haven't played it, but that sounds quite cool. I had a lot of fun in SimCity 4 optimizing train and monorail junctions!
|
|
#
?
Oct 29, 2009 01:02
|
|
|
What is the point of metered on-ramps? These are on-ramps that have short stop/go lights placed before you enter the interstate only allowing 2 cars on the interstate every second or so. I live in Arlington, VA and we have a few on-ramps here to I-66 that are metered. The only thing they seem to do is back up traffic on the ramp and people just start ignoring them. Especially when traffic is really bad in the afternoon as everyone is leaving DC.
|
|
#
?
Oct 29, 2009 01:08
|
|
|
Puck42 posted:What is the point of metered on-ramps? The thing about ramp metering is that it works best when all of the ramps in a large area are metered. The purpose is to lower the volume of traffic entering the freeway, and thereby prevent congestion and actually increase the freeway's capacity. Unfortunately, if people realize that a nearby ramp is unmetered, they'll use that one instead, negating any benefit the ramp metering would have given and congesting local streets as well. If you're wondering why keeping cars off a freeway actually increases the number of cars that are using it, several pages back I posted some graphs that explain this. Once you understand that paradox, ramp metering makes a lot of sense.
|
|
#
?
Oct 29, 2009 01:30
|
|
|
Cichlidae posted:The thing about ramp metering is that it works best when all of the ramps in a large area are metered. The purpose is to lower the volume of traffic entering the freeway, and thereby prevent congestion and actually increase the freeway's capacity. Unfortunately, if people realize that a nearby ramp is unmetered, they'll use that one instead, negating any benefit the ramp metering would have given and congesting local streets as well. ah, ok. Makes sense. I think there are only 3 or 4 metered ramps in a 1 mile area, I usually hop on the ramp that has metering but it's never turned on, but then you run into traffic as soon as the metered ramps that are turned on come up. But I think that's mostly blamed on the idiots around here that don't understand how to let cars merge on the freeway in an organized manner.
|
|
#
?
Oct 29, 2009 02:01
|
|
|
What do you think of this from an engineering standpoint? I quite like driving it its very easy to navigate. However typically the speed limit is hell slow to what I feel it can take and thus becomes a bottle neck. It's the only proper 4 way highway intersection in Australia if I remember correctly.
|
|
#
?
Oct 29, 2009 02:35
|
|
|
Puck42 posted:ah, ok. Makes sense. Several states have tried ramp metering out, but unfortunately, they only use it in a small area since it's just a test. I guess it's like building a roof for your house to see if it will stop the rain from coming in, but only putting up 2 or 3 shingles as a test. As to merging, some ramp metering systems actually put detectors in the right lane approaching the ramp. When there's a big enough gap in traffic, they give the ramp a green light. Very cool, yes? Gorfob posted:What do you think of this from an engineering standpoint? That's a 4-level stack with one pair of ramps shoved aside, and a diamond interchange stuck in there for good measure. It's quite a nice configuration for a high-capacity interchange, and the speed limit really shouldn't be much lower than that on the main line itself. The reason for all those bridges is to minimize curvature and maximize speed, after all. I was a bit wary about the separate ramps for local and freeway access at first, but their arrangement doesn't create weaving problems, and separating them gives the (correct) impression that the ramps go to two different roads. Shoulder widths look great, merges are nice and long, nice crisp pavement markings... I love it!
|
|
#
?
Oct 29, 2009 03:05
|
|
|
Oh, man! You should definitely check out Transport Tycoon. It's mostly about trains, though. It's the most fun I ever had in a computer game, especially if you play with very limited funds and high costs, forcing massive traffic on a single two-way lane  Hmm. I don't know how much you know about trains but do you have any comments on these rail intersection layouts? (Images from transporttycoon.net)  Click here for the full 1091x537 image.  Click here for the full 639x443 image.
|
|
#
?
Oct 29, 2009 07:58
|
|
|
Everyone I tell about your idea thinks I'm totally insane, Cichlidae.
|
|
#
?
Oct 29, 2009 10:15
|
|
|
Cichlidae posted:Oh duh, that would work excellently. One company (Toshiba I think?) is even producing fridge-sized nuclear units that could easily provide power for smaller ships. Check these babies out: Power Plant: Two A4W nuclear reactors with four shafts Speed: 30+ knots Range: Capable of continuously operating for 20 years without refueling  Cost: about US$4.5 billion each  Seriously, though, it could surely be done a lot cheaper if you're not outfitting and operating a gigantic war machine (though that might put a stop to the Somali pirate issue). Now I want a nuclear-powered car that needs refueling every 70 million years...
|
|
#
?
Oct 29, 2009 13:37
|
|
|
Cichlidae posted:Several states have tried ramp metering out, but unfortunately, they only use it in a small area since it's just a test. I guess it's like building a roof for your house to see if it will stop the rain from coming in, but only putting up 2 or 3 shingles as a test. As to merging, some ramp metering systems actually put detectors in the right lane approaching the ramp. When there's a big enough gap in traffic, they give the ramp a green light. Very cool, yes? California is very big on ramp metering. I cannot remember the last freeway on-ramp I was on that did not have a metered ramp (not that they are on all the time). On the newer stuff, they even mirror the red light on the back of the signal so that the CHP officers can sit on the shoulder and see if people are running the red light. Which brings me to a question. Are there any states that are ahead of the game with regards to traffic engineering and set trends for the country?
|
|
#
?
Oct 29, 2009 16:21
|
|
|
Wiggly posted:California is very big on ramp metering. I cannot remember the last freeway on-ramp I was on that did not have a metered ramp (not that they are on all the time). On the newer stuff, they even mirror the red light on the back of the signal so that the CHP officers can sit on the shoulder and see if people are running the red light. We have one freeway in Southern California where all lanes of the freeway are metered and traffic transitioning from another freeway isn't.
|
|
#
?
Oct 29, 2009 20:05
|
|
|
EssOEss posted:Oh, man! You should definitely check out Transport Tycoon. It's mostly about trains, though. It's the most fun I ever had in a computer game, especially if you play with very limited funds and high costs, forcing massive traffic on a single two-way lane The first one is a cloverleaf nested inside another cloverleaf. The second is much harder to untangle, because I see some U-turn ramps and such, but I assume it'd be analogous to two trumpets stuck together. Peanut President posted:Everyone I tell about your idea thinks I'm totally insane, Cichlidae. Well, I'd have recommended a parclo or SPUI, but you didn't want a signal. This is a pretty elegant solution! Just to make sure the weaving areas weren't a problem, I ran it through VISSIM with some assumed volumes:   Worked beautifully; no backups.
|
|
#
?
Oct 29, 2009 20:56
|
|
|
Choadmaster posted:Cost: about US$4.5 billion each That's only $37,000 per goon! I'll set up the Paypal account... Alternatively, we could just grab the Forrestal and Saratoga sitting in Newport and retrofit them with stolen Soviet nuclear cells. Wiggly posted:California is very big on ramp metering. I cannot remember the last freeway on-ramp I was on that did not have a metered ramp (not that they are on all the time). On the newer stuff, they even mirror the red light on the back of the signal so that the CHP officers can sit on the shoulder and see if people are running the red light. Certain states seem to pioneer different things. New Jersey is the king of jughandles, Florida has some cool ITS innovations, Connecticut has a pedigree of developing crash cushions for trucks. We're all in contact with each other, whether it's through traffic engineering trade shows and conferences, or just random phone calls to see how well automated de-icers or embedded pavement markings are working out. Once something is relatively accepted in the traffic engineering community, the feds start recommending it. dexter posted:We have one freeway in Southern California where all lanes of the freeway are metered and traffic transitioning from another freeway isn't. Yeah, it doesn't make sense to force freeway traffic to stop. It lowers efficiency and can create some REALLY gruesome rear-end crashes.
|
|
#
?
Oct 29, 2009 21:12
|
|
|
Speaking of Southern California, how would you fix this interchange: There's about four freeways all connecting here. The US-101 splits off from the I-5 here, the I-10 has an interchange with the I-5 here, and CA-60 merges with the traffic here. It's a horrific cluster-gently caress that is close to constantly congested. IIRC, it's the busiest freeway interchange in the world. So how would you fix this?
|
|
#
?
Oct 29, 2009 22:17
|
|
|
Instant Sunrise posted:Speaking of Southern California, how would you fix this interchange: Wow, that's monumentally complicated. I'd need to spend my career working with those interchanges to have any hope of effectively improving them. Providing sufficient capacity here is the main concern, and meeting all the standards is secondary. The most cost-effective solution, once freeways get this big, is to build bypasses and otherwise reduce the volumes. Increasing capacity at this point is a losing battle; adding more lanes would make some weaving problems, and the right-of-way just isn't there.
|
|
#
?
Oct 29, 2009 22:32
|
|
|
Cichlidae posted:Wow, that's monumentally complicated. I'd need to spend my career working with those interchanges to have any hope of effectively improving them. Providing sufficient capacity here is the main concern, and meeting all the standards is secondary. The most cost-effective solution, once freeways get this big, is to build bypasses and otherwise reduce the volumes. Increasing capacity at this point is a losing battle; adding more lanes would make some weaving problems, and the right-of-way just isn't there.
|
|
#
?
Oct 30, 2009 01:08
|
|
|
Socket Ryanist posted:There ARE bypasses--they have worse traffic than that interchange does! More bypasses, then! Dozens and dozens of concentric rings. Raze the city and pave the whole thing! You can only do so much to increase capacity. Perhaps something could be done to reduce demand: higher-density building with less sprawl, transit, ride sharing, staggering work hours... any of those would have an impact on congestion.
|
|
#
?
Oct 30, 2009 01:49
|
|
|
Cichlidae posted:More bypasses, then! Dozens and dozens of concentric rings. Raze the city and pave the whole thing!
|
|
#
?
Oct 30, 2009 02:15
|
|
|
Socket Ryanist posted:The only way to fix it is to flush it all away I'm not quite sure that's exactly what Maynard meant, but it certainly applies. Pave over it all! Then there will be plenty of room for people to drive everywhere.
|
|
#
?
Oct 30, 2009 15:24
|
|
|
Special bonus download for anyone with an interest in Connecticut's roads! Click here! It's a .kmz (Google Earth placemark) file with milepoints and volumes for Connecticut's first 85 routes; just a project of mine. The file will be available for download for one week. At the very least, you can use it to confuse your family.
|
|
#
?
Oct 30, 2009 17:15
|
|
|
Here's an interesting interchange: http://maps.google.com/?ie=UTF8&ll=40.891683,-72.483845&spn=0.02378,0.038409&t=k&z=15 As you can see, there is an exit on westbound 27 for the road which just diverged from it, which is kind of silly and redundant and I don't know why it even existed in the first place. Additionally, the split to the right used to have an eastbound connection from the upper road, with a traffic light where it crossed westbound 27. People eventually realized this was silly (since there're several other ways to get there and there isn't that much traffic) and just killed the road and turned it into a U-turn ramp.
|
|
#
?
Oct 30, 2009 17:46
|
|
|
Socket Ryanist posted:Here's an interesting interchange: The Route 27 expressway was, until 1975, expected to continue eastward, which would have likely removed the eastern "split" where North Highway branches off. The downward curvature of Long View Road below it likely shows how the expressway would curve had it been extended. What they did with the U-turn ramp there was quite creative, and I'm sure it was primarily motivated by the owners of whatever building is just north of it (looks like a hotel from the air). Otherwise, a jughandle onto Boathouse Road would be a good choice.
|
|
#
?
Oct 30, 2009 21:57
|
|
|
Cichlidae posted:The Route 27 expressway was, until 1975, expected to continue eastward. This is why I love NYCRoads. The historical overviews for LI are pretty amazing.
|
|
#
?
Oct 31, 2009 06:12
|
|
|
Deranged Hermit posted:This is why I love NYCRoads. The historical overviews for LI are pretty amazing. Wow, that's an extremely thorough site. I'd seen it linked elsewhere, but not dared to visit at work. This quote from the Route 27 page is now one of my favorites and will be used wherever possible: quote:They said if you build it they would come. They won and it wasn't built. They came anyway and now what do we have? The Connecticut equivalent is Kurumi, which has history and route data for every single state route in CT, as well as its dozens of failed expressways.
|
|
#
?
Oct 31, 2009 16:35
|
|
|
Cichlidae posted:Hey, I'd love to switch over to nuclear, and a big part of the reason I chose to work in France instead of Germany is because of their success in that field. All the same, how's that going to help us move cargo across oceans? You'd need a tremendous battery to hold enough energy for a trans-oceanic trip. Maybe you could use electrolysis to get a lot of compressed Hydrogen or a similar scheme, but that would hurt efficiency (and, therefore, the bottom line.) Winter Light posted:Do you have another source that I may have missed? Either number, that's an amazing amount of pollution. Puck42 posted:But I think that's mostly blamed on the idiots around here that don't understand how to let cars merge on the freeway in an organized manner. Choadmaster posted:Check these babies out:
|
|
#
?
Nov 2, 2009 07:18
|
|
|
GWBBQ posted:I meant nuclear powered cargo ships, the way the Navy does it. It would have to be one of the negative void coefficient designs to eliminate meltdown risk, and in case of accident or hijacking there would have to be some sort of safety mechanism to scram and jettison the reactor and let a big insurance policy to cover recovery, but once the public gets over nuclear paranoia (we're over 50% approval for new plants on land, so it's looking good,) we need to consider it as a serious option. See, this is why I wanted to be on a nuclear engineer. Problem was, a decade ago when I had that option, that more or less implied I'd be spending half my life on a sub. quote:What you have to understand about highway traffic is that if you allow a car to enter a space in front of you, you are outright admitting that the other driver's penis is bigger than yours and yielding superiority. Obviously, this can never be allowed to happen for such a petty reason as smoothing out traffic and making the commute faster and safer for you and tens of thousands of other people. That certainly seems to be the case. Interestingly, there's a legal way to force people to merge properly or get a ticket: put up "Do Not Pass" signs. Whatever order drivers are in when they pass those signs has to be maintained through the merge, or the cop sitting behind it can hand out some fat tickets. Some states even have electronic versions of those signs that automatically light up when the queue extends to a certain distance, maintaining a safe merge despite a long queue. quote:The reactors themselves are under $1B each, and each one produces more than enough power to move any of the world's largest ships. With a time to refuel of 23 years and the annual cost of bunker fuel for a 12k TEU container ship being $40-50M per year, we're looking at cost savings. If they're anything like land based reactors, after the initial lifespan they can be overhauled, refueled, and run for another 20+ years at much less than the initial cost. Imagine saving money switching to something with zero emissions. Yeah, I've looked through the EIS for a nuclear reactor (granted, a stationary one on land), and it seems like the only reason they're so more expensive on a per-watt basis than coal plants is because they're so over-designed. An airplane-proof reactor shield and massive containment vessels for waste, while coal plants shoot their radioactive waste right into the air along with sulfur compounds and a crapload of carbon dioxide? Wow.
|
|
#
?
Nov 2, 2009 13:12
|
|
|
Cichlidae posted:Yeah, I've looked through the EIS for a nuclear reactor (granted, a stationary one on land), and it seems like the only reason they're so more expensive on a per-watt basis than coal plants is because they're so over-designed. An airplane-proof reactor shield and massive containment vessels for waste, while coal plants shoot their radioactive waste right into the air along with sulfur compounds and a crapload of carbon dioxide? Wow. Coal boilers, on the other hand, have centuries of refinement and design history behind them and give me just about the biggest nerdgasm to wander around. My internship at one was the most fun I've ever had? Where else can you clean plant equipment with a shotgun?
|
|
#
?
Nov 2, 2009 16:25
|
|
|
This is just up the road from where I work: http://www.guardian.co.uk/uk/2009/nov/02/x-oxford-circus-crossing Used to be complete hell to cross. After a while you'd memorise the timings so you know when you could dash across before the tourists clogged the system up, or if it would be faster to go up the road and back down again. 40,000 pedestrians/hour blew my mind though.
|
|
#
?
Nov 2, 2009 18:46
|
|
|
I've skimmed over this thread and don't know if it was answered. But you had asked how the floating bridges in Washington accommodate for movement. Both bridges utilize expansion joints at each end to prevent them from failing. WSDOT's picture set from the July 2009 replacing of the I-90 (Homer Hadley) Floating Bridge expansion joints -- http://www.flickr.com/photos/wsdot/sets/72157616718432350/ What's an expansion joint and how does it work? (I assume you know, others may not) - http://www.youtube.com/watch?v=-GSVT3dO0LY&feature=related (part one) http://www.youtube.com/watch?v=NyhvEoEZHyg&feature=related (part two)
|
|
#
?
Nov 2, 2009 21:48
|
|
|
Groda posted:Nuke eng here. If anything, they're extremely underdesigned. The steam cycle is far less efficient that it could be for safety reasons (fewer vessel/containment penetrations, less hands-on maintenance, validatability) and economic reasons (their specific operational cost is stupid low). The more boring they are, the safer they are. What I mean by "overdesigned" isn't that they don't operate at high efficiency; it's that a nuclear plant is required to meet much more stringent specifications (like the aforementioned plane-proof dome) than a coal plant, and boatloads of permits and paperwork to boot. If we built all of our coal plants to be impervious to terrorist attacks, store all their waste in a responsible way, and not include multiple redundant safety systems for each component, then coal plants would cost billions, too. quote:Coal boilers, on the other hand, have centuries of refinement and design history behind them and give me just about the biggest nerdgasm to wander around. My internship at one was the most fun I've ever had? Where else can you clean plant equipment with a shotgun? Wow, you've got to tell me about that!
|
|
#
?
Nov 2, 2009 23:43
|
|
|
TokenBrit posted:This is just up the road from where I work: That's amazing! As many peds per hour as cars on the world's busiest freeway. I like the landscaping; it really delineates pedestrian area, and, from the video, tends to keep them in line.
|
|
#
?
Nov 2, 2009 23:48
|
|
|
|
| # ? May 17, 2024 18:30 |
|
|
Cichlidae posted:Wow, you've got to tell me about that!
|
|
#
?
Nov 3, 2009 00:39
|
|
