Unlocking the mysteries of the random traffic jam

Posted by freedomforall 9 years, 5 months ago to Technology
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Have you ever seen a 2-mile long traffic jam on the opposite side of the highway and thought, “Gee, I didn’t see an accident back there, I wonder what happened?”

Or maybe you are cruising along at 60 mph and suddenly you slow to a stop. You then sit stationary for 30 seconds and just as quickly you are back to cruising at 60. What happened?
SOURCE URL: http://fleetowner.com/blog/unlocking-mysteries-random-traffic-jam


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  • Posted by $ Susanne 9 years, 5 months ago
    Part of the phenomenon is the lane next to yours will be moving faster. Always. Of course, everyone will move over to *that* lane, and it slows down. The other rule is this - what we were taught was the "fast lane" and "slow lane" are reversed - I see "trains" of people doing 5 under the limit in the left lane (usually behind a self-appointed traffic regulator) , and people sailing by in the right.

    Or go to L.A. People will sit and wait in a left turn lane, green arrow going, no one coming... then when it turns yellow, 5 or 6 cars blow through the left lane. I have asked people, and no one seems to know what's that one about... but everyone does it. (I typically "run" green lights down there, sure enough, the car behind me faithfully stops and waits for a yellow...)

    I don't miss driving in commute traffic - not at all!

    We get our own, tho. Speed limit is 55. You come up behind someone doing 60 (and you're doing 65 or so) and they slow w-a-a-a-y down to about 40-45, as long as there's a double yellow line. Once the passing lane comes up, they're back up to 70+... until it ends, then back to 40-45.
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    • Posted by jimjamesjames 9 years, 5 months ago
      I grew up in LA, learned to drive the freeways there, took those skills to Wyoming and now, a traffic jam is six cars at a stop light. Geeze, I love Wyoming!!! LOL
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      • Posted by WyoJim1963 9 years, 5 months ago
        I totally agree, after 24 years in the Bay Area, I moved back to Wyoming. What a relief it is!
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        • Posted by $ Susanne 9 years, 5 months ago
          I've been gone from that area for 3 years - had to go back for a meeting, forgot how sucky the traffic was, and how fast it goes from fair to ugly.

          It takes a special skill set - I call it Combat Driving 101 - to survive the freeways there. LA is bad but predictably bad (and at least the radio is pretty accurate). The SF Bay Area... you never know what it's going to do, and radio traffic reports - fergeddaboudit - 20-30 minutes out of sync with reality.
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          • Posted by WyoJim1963 9 years, 5 months ago
            When we left Livermore in 2005, it would take up to an hour to go the 10 miles to Pleasanton/Dublin area. And that with five lanes each way! No desire to ever go back to that again.
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            • Posted by plusaf 9 years, 5 months ago
              In '78 I moved from NJ to Silicon Valley for a new job. I marveled at the "smooth roads and polite drivers."

              24 years later, I moved to Raleigh, NC, and once again, marveled at the improvement: Smooth roads and polite drivers.

              Ten years later... same old same old, but now i'm seriously retired and almost never have to drive in rush hour traffic... which is, btw, about 4-5 pm here, while it was 3-7 pm back in CA's technology opus of Silicon Valley. Go figure.
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      • Posted by $ Susanne 9 years, 5 months ago
        You have stop lights? What's it like? --giggles--
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        • Posted by plusaf 9 years, 5 months ago
          Around Eagle, CO, they've been replacing traffic signals with roundabouts just about everywhere. Vail, too...

          Here in Raleigh, a few roundabouts have been implemented, to the annoyance of a lot of locals, but where they'd REALLY do a lot of good, like on '70 at Brier Creek Shopping Center, nobody seems to have the vision to give it a moment's thought. Sad.
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          • Posted by 9 years, 4 months ago
            People need to learn to use roundabouts properly, too, or they don't have the proper traffic smoothing effect.
            I worked on the planning of the 'new town' Woodlands, Tx in the early 80's and there was no interest in using roundabaouts even though there was plenty of space to implement them. The main thoroughfare (at that time) has light after light after light today. I spent a couple weeks there a few years back and did a computation of the percentage of times that I had to stop at intersections with traffic signals while on the main thoroughfare and it was about 75-80%. That road has very wide forested esplanades between the lanes of opposing traffic and roundabouts would be easy to implement, and eliminate the endless cycling signals needed to allow left turns across those wide esplanades. Its very much a "not invented here" blindness, I think.
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            • Posted by plusaf 9 years, 4 months ago
              And I drove the infamous Somerville Traffic Circle in NJ for decades, too... To 'solve the problems of gridlock at rush hour' they actually built a flyover for the most heavily-trafficked route, and THEN added traffic signals a few blocks ahead of the mergers to the circle to 'throttle traffic,' which didn't really help at all, as everyone raced to the Circle's entrance after the lights had bottled them up for minutes at a time...

              All of which were seen as better solutions than putting up signs at the merger points that said, "No, YOU Yield to traffic already IN the circle!"
              At least Raleigh put a few like that in when they converted two bottlenecks in the City to roundabouts...
              :)
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  • Posted by Robbie53024 9 years, 5 months ago
    Another pet peeve are the idiots who just "have to" drive in the left lane - at any speed they choose is proper. I've seen people merge on to the highway where there is no vehicle in the right lane for a long ways, and they immediately move to the far left lane. I've taken to driving in the right lane most of the time. It is often clear and when I do come upon a driver not moving at my desired speed, it is generally easy to go around them.
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    • Posted by IndianaGary 9 years, 5 months ago
      ...along with all of the idiots in pickup trucks that just HAVE to back in to a parking spot, then go back and forth to position their truck "just so" while everyone else in the parking lot waits. This happened to me this morning and I had another idiot behind me yelling (at me, I think) "Get the f..k out of my way!" He was about 10 seconds away from a full-out road-rage attack when the truck in front of me finally got out of the way and traffic could move. I think I'll name this a "parkiton".
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      • Posted by plusaf 9 years, 5 months ago
        the other night in a mall parking lot, some moron honked, flashed his high beams and passed me as I was waiting for someone to back out of a parking space I wanted to occupy.

        Morons everywhere... no city or state has a monopoly on 'em. Stories without bounds.
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  • Posted by Non_mooching_artist 9 years, 5 months ago
    I call it the "RBT", or Random Braking Technique. When a stupid person, usually in the left lane, just hits the brakes for some random reason, slowing things down just enough so the people behind must now tap the brakes... This leads to traffic for no good reason.... And causes my head to explode...
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    • Posted by Robbie53024 9 years, 5 months ago
      Or, the idiot who moves from one lane to another with too little room, causing the driver of the car following to brake, and then the cascade begins. I have used a mathematical simulator to show that if as few as 2% of drivers change lanes - at any speed - that all arrive at a slower rate than if all stayed in their initial lane.
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      • Posted by $ Susanne 9 years, 5 months ago
        I found if I go slower (not my much) than the car in front of me I'm not going from brake to accelerator, the cushion makes up for it. Of course, people come in, cut in front of me, and then hit their brakes...
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        • Posted by Robbie53024 9 years, 5 months ago
          You don't have to go slower, just maintain the gap. Then, you can use it as a buffer for when traffic slows slightly. But yes, you will get those who cut in front, and then you will need to hit the brakes.
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        • Posted by $ jdg 9 years, 5 months ago
          Which is why that technique (1) doesn't make sense, ever, and (2) makes everyone behind you desperate to pass you.
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          • Posted by $ Susanne 9 years, 5 months ago
            Makes less sense to jam on that accelerator to get in front of someone so you can hit the brakes, and continue the stop and go cycle. It makes about as much sense as getting angry and agressive behind the wheel - does getting there 5 or 15 seconds faster justify stress and anger, especially behind the wheel? Is it worth missing the cues of the driver 2 up - and slamming into the car you misjudged cutting in front of someone? Does it really work, shaking your fist or flippinf someone off - from behind your moving glass cage, where you know its safe?

            I'm just curious why driving safer makes no sense... and why people have to be so "desperate" to be first in line, even tho you'll still get 10 feet up the road in the same amount of time?
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            • Posted by $ jdg 9 years, 5 months ago
              Because your method makes the slowdown worse for everyone behind you, and thus provokes them. If they ran you off the road, they'd be justified.
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              • Posted by plusaf 9 years, 5 months ago
                ok, THAT did not 'advance the conversation, any more than your post above it....

                I leave that 'cushion' for MY safety, and if someone plugs the hole with their car from the right or left lane, I slow down and re-establish the cushion for MY safety. Generally, the folks one or more cars behind me don't even notice my 'cushion' so your scenario isn't part of MY real life. But I sure as hell don't let my cushion space get to be more than about 3-seconds long.

                That means "car lengths of space" are hard to guesstimate while driving, but if you can count 2-3 seconds 'gap' between you and the car in front of you, it drastically lowers your chances of being caught by surprise by the driver in front of you.

                Think what you want, and don't believe a word of what I say, but I've been driving an average of 10-12k miles per year since I got my license in 1963 (do the math) and have been involved in only one fender-bender where I was at fault and I've gotten EXACTLY ONE speeding ticket in my life (and none when I drove my '69 seven-liter Corvette for about 42k miles.)

                Ah, but what the fuck do _I_ know?
                Enjoy your beliefs....
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    • Posted by plusaf 9 years, 5 months ago
      I recall a study that showed that if one person suddenly slows for a traffic signal that's changing, odds are best that the FOURTH car behind them will either rear-end the third one back or be rear-ended themselves.

      Has to do with human reaction times in 'surprise' situations. Leave extra room and it's less likely to happen to you. Works for me. Good luck!
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  • Posted by JanelleFila 9 years, 5 months ago
    I got stuck in traffic last night, completely stopped as I tried to merge on the freeway. I thought for sure there was a nasty accident. About a mile ahead the construction dropped the highway from two lanes to one lane. As soon as I passed the merge into one lane, everything sped back up. I've never understood why that backs traffic up so badly. I personally think it is because people ignore the signs and wait to the very last minute to merge out of a closing lane.
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    • Posted by IndianaGary 9 years, 5 months ago
      It's because of the "blivit". A blivit is when one tries to put two pounds of crap in a one pound bag. Then there is always the jerk who refuses to let anyone in front of him as if he'll get to his destination sooner that way.
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    • Posted by $ jdg 9 years, 5 months ago
      You're forced to wait until the last few feet by the fact that if you don't, people will pass you in the closing lane and then force their way in front of you.

      I've seen better behavior in states that post "Take Turns" signs at these places.
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      • Posted by plusaf 9 years, 5 months ago
        You can see the same 'take turns' effect, or lack of it, if you're leaving a large parking garage after a concert or other entertainment event. Some jerks just HAVE to be first in line.

        A close friend just assumes that those drivers are members of the 'teeny-weenie club.' Makes sense... :)
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      • Posted by JanelleFila 9 years, 5 months ago
        I hate when people zoom past you when obviously there is a long line for a reason! I love when trucks veer into the other lane to block it off. I try that sometimes, but people still fly by, and that makes me super nervous.
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        • Posted by plusaf 9 years, 5 months ago
          Yep, back when I first moved to NC, I blocked a large pickup truck from merging just for the sake of merging and 'getting there first on his part.'

          And the driver cut me off, nearly taking off my left front fender, then slowed in front of me to a crawl and parked in front of me when I pulled off on the shoulder down the road a bit. He eventually gave up and blasted down the road, but it taught me that it's not good karma to piss off anybody who a) has a huge boy-toy truck under his butt or b) might be packing heat to prove he's a 'real man.'

          Slow and steady gets you there in one piece.
          imnsho... :)
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          • Posted by JanelleFila 9 years, 4 months ago
            What a scary story! That's the thing about road rage, it is such a real and dangerous threat that you have to bear in mind. I try not to engage with other drivers because you are so right, you just never know what kind of unstable person might be behind the wheel in the lane across from you.
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            • Posted by plusaf 9 years, 4 months ago
              Roger that... MANY years earlier, I flipped off a big rig driver who didn't like me getting in front of him after a traffic signal changed on old Route 69 in NJ (Now Route 31, I think... =100-69...)... he soon passed me and nearly cut me off with his trailer, then slowed down and 'waved me around to pass him...' into oncoming traffic.

              So I just went a lot slower. I was on salary and on my way to a business meeting. He was probably hourly and every minute he dawdled cost him much more than it cost me. Eventually he put the hammer down and disappeared, but that was also part of The Lessons Learned.

              Oh, and that reminds me of the time I found myself in a merger-jam approaching one of the tunnels going to Manhattan. A larger, much more expensive car's driver wanted to squeeze me out. He lost that one. My wife complained: He's going to hit you! ... I replied, No, he's not. She asked why... I answered, Because he owns that car and this is a rental. I ended up in front of him into the Tunnel. Ah, the memories of having driven something over 500 or 600k miles in my life.. :)
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    • Posted by Robbie53024 9 years, 5 months ago
      Correct. Instead of merging and adjusting distances smoothly, they try to jam in at the last possible moment, causing the following drivers to slam on their brakes - which then cascades.
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      • Posted by 9 years, 5 months ago
        But bottom line is 2xlane cars into 1 less lane equals a traffic problem until either traffic load is reduced or lanes are increased. Merging sooner spreads out the slowdown, but not using the lanes available for their entire length does not solve the problem.
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        • Posted by $ Susanne 9 years, 5 months ago
          It doesn't matter if people run that lane or not, they'll still be in that queue moving over... it's the people who say "the HE!! if I let YOU cut in front of ME, I'll just CUT YOU OFF and SHOW YOU!!!" that cause the jams. And the accidents from not letting someone in (that shuts the highway down. Everyone is so afraid to let someone get in front of them, because, Horrors of horrors, you're less of a tough independent driver because someone got in front of you, and you might be 3 1/4 sedonds later than you were otherwise??

          Strangely enough... I've driven in Italy, the UK, Germany, France, Russia, etc... people don't have this weird "no-cutsy's" routine the dolts do in the states - they see someone comig up beside them, they either speed up or slow down to let them in. Traffic slows down, sure, but it works.
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          • Posted by $ jdg 9 years, 5 months ago
            Rewarding theft only means you get more of it. The one guy you let in can easily turn into 20 by the time you get an opportunity to pass. Don't be Neville Chamberlain!
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          • Posted by 9 years, 5 months ago
            I agree, drivers in Australia and NZ are very courteous and almost everyone lets other cars in the line whether its a merge or just someone entering from a parking lot or side street.
            BTW, hogging the 'fast' lane is a ticketable offence in both Oz and NZ. There is virtually no fast lane road hogging based on my experience. (Plenty of speeding tickets are issued and speed cameras are ubiquitous.)

            You have to drive overseas for a while to appreciate the advantages of round-abouts, too.
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  • Posted by $ Snezzy 9 years, 5 months ago
    Anyone who has studied fluid mechanics has pondered over whether the equations for motion of particles in fluid flow might also apply to highways.

    A related phenomenon is the understanding among police that the very last car in a bunch of cars can be seen driving faster than the first car. How can this be possible? Well, the last car is the recipient of the slowing-down and speeding-up that occurs in the middle of the bunch. So at some point he may be going quite a bit faster, to catch up with the rest of them. Also, as the very last one, he's easier to pull over and ticket.
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  • Posted by plusaf 9 years, 5 months ago
    I've seen that 'backward wave propagation around the circle' video before, but I think it was a few decades ago. Suddenly coming to light now?

    Notice where more urban/suburban slow-traffic crawls happen on interstate highways... right around on-ramps around rush-hours.

    If everyone stuck to the left two or three lanes and let the right lane alone for entering and exiting, speeds in the #1 and #2 lanes would at least double. I figured this out at least 20 years ago, watching traffic and backups in Silicon Valley. Now I see the same on the ring-road interstates around Raleigh.

    This is not rocket surgery, kids! It's lousy driver education and attitudes and wrong-headed 'solutions' by alleged 'traffic engineers.'

    ah,... whatever... who listens...?
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    • Posted by $ jdg 9 years, 4 months ago
      It'd do more good if idiots who won't keep up were compelled to stay OUT of the left lane. This is already the law in many states, but seldom enforced.
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  • Posted by Herb7734 9 years, 5 months ago
    Looks a lot the way ants act.
    Who really knows who the dominant species were from say, 100 million years up until now? There is still part of our brains that reflect the mindless, strictly reactive beastie in all of us.
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  • Posted by 9 years, 5 months ago
    Yes, I posted this because on Tuesday I was stuck for 15 minutes and after that all cars just accelerated to 65 mph with no evidence of mishap anywhere (on I-10Westbound east of Atlanta.)
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  • Posted by $ allosaur 9 years, 5 months ago
    Now I can say "jamiton" when this happens in the Birmingham area, especially on I-65 which runs north and south through the west side of the main city. The suddenly slowed down line of traffic will just speed back up after a few minutes for no visible rhyme or reason.
    By the way, I-65 passes through an intersection with I-20/59 that TV and radio reporters have long called "malfunction junction." Years apart, I've seen two cars spin out there in the rain and crash against a guard rail. There a tractor-trailer truck changing lanes ran me off the road and I just barely stopped before a parking lane ended with a concrete barrier.
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