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So bookmarking this thread. The question I had goes to your discussion of the 85th percentile speed. I've heard of ideas being kicked around of setting a variable speed limit based on the 85th percentile of whatever the current average traffic speed is; has there been any serious thoughts of implementing something like this in the US? (I think I remember reading somewhere about a system like this in Germany).
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Jul 28, 2009 01:30
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| # ¿ Apr 26, 2024 18:29 |
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Hey, check out this clusterfuck:  I'm including a link to the google map because a screenshot doesn't really capture the horribleness that is the 6th avenue freeway. http://maps.google.com/?q=&ie=UTF8&ll=39.725434,-105.014738&spn=0.005883,0.013733&t=h&z=17 The entire length of W 6th avenue is pretty terrible, but I have probably nearly gotten killed in this interchange more than anywhere else I've ever driven. The highway goes from 9 lanes (including the collector/distributor road and the ramps) at bryant, where the speed limit is 55mph, down to a 5 lane, one-way 30mph street as you get past the interchange to the east. The ramp geometry looks like it was designed by a 4-year-old with crayons. The acceleration lanes, where they exist, gain and loose lanes seemingly at random. The weaving, oh god, the weaving. I'm fairly sure that the Colorado DOT has this on their radar; I'm equally sure that the reason it hasn't been fixed yet is anytime someone looks at the cost estimates they just twitch a little and then pass out. Here's another interchange from the same road that's always loads of fun:  See the ramp from NB 121 (Wadsworth) to EB US-6? There is no acceleration lane there. None. You have from the last bend until where Vance street is to get to highway speed, which in this part is 65MPH. I can maybe make it to 55. Most people just swerve into traffic at about 40-45.
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Aug 11, 2009 17:50
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drat, I really like your design for that Wadsworth/6th ave. interchange. After hunting around on cdot's website, I managed to find the EIS they apparently did on that, and it looks like they want to go with a tight diamond with a loop in the upper left quadrant (from WB US6 -> SB Wadsworth). This, apparently, will involve a great deal of knocking down houses, so I suppose CDOT feels they haven't been picketed enough lately (it's mostly been RTD, our regional tranist authority, as they get ready to install about 120 miles of rail transit over the next 6-7 years). As I was poking around, I found another thing that I wanted to ask about. There are a couple of heavily used bridges that form part of I-25, and there was mention of the "sufficiency rating" being 20.2 and 22.8, with 50 being considered "acceptable." I guess what I'm wondering is what the threshold is for "oh god, oh god, we're all going to die."
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Aug 12, 2009 01:09
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Socket Ryanist posted:Overhead LED signs I think, possibly with cones? Nothing solid. Probably the physical wall of cars is enough.
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Sep 26, 2009 06:05
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Oog, that seems like it could cause problems. Everywhere I've seen is "flashing red means the same thing as a stop sign". And I've seen the occasional stop sign in an isolated rural area that had a double flashing red like that to mean, "REALLY VERY MUCH STOP HERE, DUMMY". What's wrong with just doing solid red, solid yellow, separate flashing yellow (or green) with a big "EMERGENCY SIGNAL" sign? That's the way I've seen it just about everywhere, and everyone knows what a solid red light means (and if they don't, the big goddamn fire truck with all its lights on would probably be a tip-off).
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Nov 6, 2009 03:39
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Speaking of lane markings, I was curious as to how those "turtle shell" markings are installed. I don't know what they're actually called; I encountered them a lot during a recent road trip around the pacific northwest; they're the kind that are just a raised half-shell in the middle of the road, usually installed a few at a time, and seemingly instead of actually painting a stripe on the road (like, they'd just have a row of 3 or 4 of these bump things in the middle of the road, and no other lane markings at all). This was particularly in Oregon, where they seem to have some really odd highway conventions (such as all the speed limit signs in the state saying "SPEED 40" instead of "SPEED LIMIT 40"; I've never seen that in any other state). While I'm on the subject of road trips, holy poo poo California. I don't think I've ever seen such insane highway design. "This highway's a super-2! Now it's a 4-lane! Whoops, now it's a rural two-lane with no shoulders! Now we're going to drop the speed limit to 40 because some developer started putting in a street grid but "lost his financing" halfway through! Ahahahahahaha!"
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Nov 9, 2009 18:36
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Choadmaster posted:LOL. At least we put so many emergency phones on them that you literally don't have to walk more than a half mile to call someone! (Once that comment might have been serious, but now... why do we maintain the damned things?) I think the road that actually prompted that was SH-99 (was doing a big-rear end road trip involving a bunch of national parks). I've seen highways that will split from a 2-lane undivided to a 4-lane divided when theres, you know, some reason to do so (like a nearby population center). That thing was just changing back and forth every couple of miles for no apparent reason whatsoever. I think they may have planned it during the housing boom, cause there were a number of apparently abandoned housing developments in the area (just the start of a street grid and nothing else). And for the emergency phones, I've actually been seeing a bunch of newish ones; I think the current strategy is to put them in places where you have no hope of getting any sort of cell phone coverage (Colorado has a bunch of these scattered around in the mountains still).
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Nov 10, 2009 23:25
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Christ, I wish they'd do the "blocking the box" thing here in Denver. The problem is due to our... "unique" downtown layout, we've got some really odd sized boxes, so I don't know if it would help.  This is a bad intersection. I do not like this intersection. It is the intersection of 3 one-way streets in downtown Denver. You will notice that while Broadway and 18th ave are normal, north-south-east-west streets, Tremont and 18th st (the unlabeled one at the upper left) are not. This is because the people who originally laid out the street grid here were stupid. The entire downtown street grid is skewed at a 45 degree angle to the the streets in pretty much the entire rest of the greater Denver area, so you get really retarded intersection layouts like this one. During rush hour, people going southbound on Broadway constantly block the intersection, because I guess little cat tracks are really easy to confuse with the gigantic stop bars when you're talking on your cell phone and putting on makeup and eating a cheeseburger while driving, all apparently with your feet. So what ends up happening, is people on Broadway get a yellow light, they panic and decide to try to blow through the intersection, there isn't enough room on the far side past Tremont (which is where they have to get to), so they either stop right before the first set of cat tracks leading from 18th ave to 18th st (which is usually fine, as you can still get around them), or at the second or third set (which is bad, because it blocks lanes), or right in that little no-man's land between the 18th ave->tremont tracks and the 18th ave-> 18th st tracks (which mostly just pisses people off and causes a lot of honking).
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Dec 30, 2009 18:20
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Do loop sensors "count" the cars? By which I mean, if the loop sensor is long enough to sense more than one car in the queue, does it actually do so, or detect a second car pulling up in an adjacent lane? Or is it just, "ayup, theres something there, better start the countdown timer on the other movement". And on an unrelated note, I was looking at those HAWK signals a few pages back, and the more I think about it, the worse the idea seems to be to me. It's basically a completely unfamiliar type of traffic signal, with the disadvantage that it looks sort of like a normal light. What's the argument for using those over, say, a normal red-yellow-green traffic light that just stays green all the time unless the ped signal is actuated? Or for that matter, if it's a lower volume street, something like this:  Those are starting to pop up all over the place in Colorado, and they seem to work really well. The flashers in the sign are super bright LEDs with a kind of irregular flash pattern (sort of flash--flash--flashflashflashflashflash), and are often combined with similar in-pavement flashing LEDs. It not only draws the drivers eyes to the big sign saying "STOP FOR PEDESTRIANS DUMBASS", but also looks different enough from a traffic light to avoid confusion. I've also seen a version that incorporated a magnetic loop detector to set it off for bikes approaching the crossing, which I thought was pretty cool. I've also been noticing that the local authorities don't seem to be wasting any time now that the new MTUCD is out; I've started seeing those shared use lane markings showing up all over the place. There aren't really enough bikes on the road to see how well it works, but I guess we'll find out as the weather starts getting better.
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Feb 12, 2010 18:31
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Cichlidae posted:Has your state approved the MUTCD yet, in full or in part? It might be hard to find out, so I'm not expecting an answer, just wondering I don't think they've adopted the 2009 one yet, as far as I can tell (Colorado, if you were wondering). They did adopt the 2003 version, and there's a law on the books requiring adherence to the federal standard (plus a state-specific supplement, all of seven pages long, mostly just clarifying a few provisions of law), so I imagine they'll be adopting it pretty soon.
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Feb 13, 2010 07:33
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Hey, so this may have been brought up earlier, but in conjunction with the thing about speed limits, exactly which oatmeal head decided it would be a great idea to have all the truckers go 15mph slower than everyone else? I mean, I can understand it in certain unusual circumstances (steep grades, say), but why is it safer to have all the trucks doing 55 in the right lane, and all the cars weaving between the trucks and the passing lane (keep right laws, doncha know) at 70?
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Apr 12, 2010 04:28
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Entropist posted:I encountered this last week, the signals were off completely. Probably a local blackout. Huh. Where I am, if the lights are out completely, you're supposed to treat the intersection as an all-way stop. Which nobody does, and it always seems to happen at intersections that have like 3 through lanes in each direction, plus a right turn lane, plus a double left... total chaos. Americans are the worst frigging drivers in the world. I have seen (in other parts of the country), some sort of automated fold-down stop signs on the overhead traffic light mounts, presumably held closed with a solenoid or something for when the power fails. I frankly doubt it helps much.
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Aug 18, 2010 21:29
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 Should have voted for that bond issue, fuckers! (Yes, it's a 'shop)
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Aug 21, 2010 02:57
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Baronjutter posted:I see tthe carpool/bus lane on the highway but what's the thick white lane with the chevrons? I went up and down the highway and didn't see a single car in there, are they off limits? In my state (CO), two white lines with chevrons is the same as a double-white, in other words, "do not cross". They use the chevrons if the lines need to be more than <some distance> apart.
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Jul 27, 2012 21:57
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Those are pretty cool, although I wonder if they'd probably work better in situations where their use would be fairly rare. I live in Colorado, and the runaway truck ramps here are used approximately "all the goddamn time", so they tend to go for cheap and effective. Here's one on the stretch of I-70 leading into Denver; it's on the far right side, basically just a long stretch of thick gravel with a whole bunch of water barrels at the end (not visible here, it's a long-rear end ramp since it's on a downgrade): In other areas on I-70 I've seen where they just stick the ramp on about a 20% up grade off to the side and let gravity do the work for them. On a related note, one can divine a certain sense of exasperation on the part of the Colorado DOT:   The beacons on that one all blink simultaneously. Truckers don't notice? Slap some more yellow lights on! (pictures are all from here) potato of destiny fucked around with this message at 04:02 on Aug 8, 2012 |
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Aug 8, 2012 03:59
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DTurtle posted:Here in Germany every intersection with traffic lights also has normal right of way traffic signs. At night, main routes have the traffic light turned off, while the side routes have flashing yellow. This is just to add warning for the side routes. What counts are the signs. Here in the united states, if the lights are out, drivers will naturally assume that the world has ended and we are now embroiled in a post-apocalyptic fantasy where only the strong may survive unto the far side of the intersection. I mean, technically it's supposed to be a four way stop, but those are rules of the dimly remembered past before the lights went out, and we can scarcely be expected to follow those nebulous "rules" of the forgotten before-time at the expense of being delayed from picking up our kids at soccer practice by even four seconds. Americans are basically the worst drivers in the entire world, is what I'm saying.
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Aug 15, 2012 02:25
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grover posted:Milton Keynes was a horrible failure of an attempt to recreate an American-style urban area. It's definitely not representative of American urban planning. If nothing else, 90% of Americans would poo poo themselves at having to deal with that many roundabouts.
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Aug 25, 2013 22:53
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misguided rage posted:Yeah, that's the situation I was trying to describe. It's currently not really possible to have permissive lefts in that setup; leaving the light off and letting the green through light act as a 'permissive lefts are okay now' indicator like you would normally is ambiguous as hell. Having a standardized 'permissive lefts are allowed' signal could be helpful. What I've seen in this situation (and I think it's what the latest MUTCD says) is to have four elements instead of 3, with the extra one being the flashing yellow. The purpose of having four lights (  ) is so that you can have a protected left turn followed by a permissive left turn, and have a visual change in position between the solid yellow and flashing yellow phases. What they used to do is have that little "pyramid" formation, where you have a 5-element fixture, with green and yellow arrows on the left, green and yellow balls on the right, and a red ball centered above both. The problem with this is you have a phase where there's a red ball and a green arrow in the same lane, creating ambiguity.
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Aug 27, 2013 02:12
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| # ¿ Apr 26, 2024 18:29 |
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kefkafloyd posted:The VMS programmers here in Mass have gotten a little more clever/jokey over the past year. This coincided, of course, with taking suggestions from people for slogans to put on the VMS. Colorado DOT has been doing this one all over the place:  I think they jinxed it 'cause all the ski resorts are opening late. 
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Nov 7, 2014 00:34
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