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Science

Chaos and Your Everyday Traffic Jam 477

Posted by timothy from the could-often-be-my-dad's-nutty-driving dept.
An anonymous reader writes "What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever? Is it simply the fact that most people just don't have a clue how to drive? That's very possible, and in reality there are so many variables involved in something like a traffic jam. But is it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver who was in too much of a hurry?"
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Chaos and Your Everyday Traffic Jam More

Chaos and Your Everyday Traffic Jam

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  • Passion of Traffic (Score:5, Funny)

    by P(0)(!P(k)+P(k+1)) ( 1012109 ) <math.induction@gmail.com> on Wednesday December 27, 2006 @04:12AM (#17374704) Homepage Journal

    From TFA:

    So the next time you find yourself stuck in bumper to bumper traffic, it's very possible that the jackass that caused it is already at home watching the latest episode of American Idol[...].

    I like the idea of a single blameworthy agent to bear the brunt of my hideous imprecations: a Christ of traffic, if you will; except I'm the Romans, and it's Mel Gibson's Passion all over again.

    • Specific to Albany, NY area (Score:5, Interesting)

      by Phreakiture ( 547094 ) on Wednesday December 27, 2006 @08:37AM (#17375716) Homepage

      In our area, there is a twice-daily traffic jam that has been understood for years, but fixing the road to take away the problem would be ungodly expensive.

      There is, actually, nothing technically wrong with the road. The road in question is I-87 (the Northway), and the pinch point is where it crosses the Mohawk river. The Twin Bridges have a slightly narrower shoulder than the highway leading up to them in either direction, but the shoulder, on both sides of each bridge, is still every bit as wide as any of the three lanes going in either direction.

      Compounding the problem is that the bridges are (hope this is the right term) truss bridges. There are two convex bowed beams that go over each side of each bridge, and a construct of triangular trusses between them. These are the reason why a change would be ungodly expensive, because you would have to rebuild the bridges.

      Anyway, people come to the bridges and slow down because they perceive that the road has gotten narrower, while failing to perceive that this fact is irrelevant. This slowing down leads to the accordion effect that was described in TFA, where successive cars have to apply more and more braking in order not to hit the car in front of them. By the time you are a mile north of the bridge in the mornings (south in evenings), traffic is basically stopped.

      The construct that causes all of this trouble can be seen here [google.com] (along with some Google wierdness in the construction of the image).

  • Site jammed up (Score:5, Funny)

    by johnw ( 3725 ) on Wednesday December 27, 2006 @04:16AM (#17374718)
    Only three comments and already the site seems to have been totally jammed up by a single Slashdot article in too much of a hurry.

  • I know, I know!! (Score:5, Insightful)

    by quokkapox ( 847798 ) <quokkapox@gmail.com> on Wednesday December 27, 2006 @04:16AM (#17374720)

    "What causes these mysterious traffic jams that continually appear throughout the day for no reason whatsoever?

    Too many cars?

    • Hey, look, the obvious has made it to the front page of Slashdot disguised as an article again.

      If some bonehead makes a bad driving maneuver, he might cause a traffic jam. And whether or not he actually causes a traffic jam is dependent on how many cars are on the road!

      This whole thing is just dumb. Yes, if all drivers drove perfectly, then we could push more cars through the same piece of road. But that's not the way it works. Roads don't have a hard capacity. As the number of cars on the road increas
      • at 140 cars a minute a traffic jam is virtually certain.

        But if there is a traffic jam, you aren't going to be pushing 140 CPM. I have a feeling that CPM will stay mostly constant and the speed will vary inversely with the total number of cars. Therefore, you would never get enough cars going fast enough to hit a CPM that makes a traffic jam certain (self-limiting). Or maybe it's late and I'm going crazy.
        • It's just that the capacity (bandwidth if you like) of the road is extremely variable.

          If someone decides to drive slowly that reduces the capacity all the way up the road behind him. Similarly if (as seems to happen a lot around here) the authorities put an artificial speed limit on the road for 'traffic management'.

          If you have 120CPM, and the road capacity is 140CPM - no jam.

          As soon as someone decides they're too scared to drive at the speed limit.. road capacity drops to 100CPM.. jam.

    • Re: (Score:3, Interesting)

      by iangoldby ( 552781 )

      But is it possible that the entire traffic jam could be both the continuing and end result of a chain reaction set in motion by a single driver who was in too much of a hurry?

      No, it isn't possible that a single driver could be the cause. The mechanism described in the article relies also on a large number of other drivers all following too close to the car in front. If enough people kept a safe distance from the car in front, the shock wave caused by the sudden movement of one car would die away instead of

      • But it didn't say cause, did it? It said "set in motion," which is a much better description of what happens. The first domino sets the chain in motion, but if there are no intermediary dominoes, there will be no chain.
        • This is why slashdot sorely needs a "retarded" moderation.

          Definition of "cause" [reference.com]

          1. a person or thing that acts, happens, or exists in such a way that some specific thing happens as a result; the producer of an effect: You have been the cause of much anxiety. What was the cause of the accident?

          "The producer of an effect" sure as hell sounds like "set in motion" to me.

    • Re: (Score:3, Interesting)

      by UbuntuDupe ( 970646 ) *
      Good (if obvious) point. A traffic jam can be caused by too many cars, by stupid drivers, or by both. For example, if a high capacity road has to "dump its load" onto an intersection with a traffic light, the traffic will still back up, regardless of the mental abilities of the drivers. On the other hand, I've seen traffic back up, even when the freeway is well below capacity, simply because of the right combination of stupid drivers. Such as when the two people in the middle and outer lanes decide to d
  • Where I live, we don't have traffic jams.

    In a community of about 70 people covering 50 square miles, it's not hard to imagine why traffic jams are nonexistent.

    I used to live in Houston. After years of moving back here, I've nearly forgotten what traffic jams are like.

    Around here, the closest thing to a traffic jam is me. Even the old people think I drive too slow.

    • Re:Where I live ... (Score:5, Funny)

      by Patrik_AKA_RedX ( 624423 ) on Wednesday December 27, 2006 @05:16AM (#17374930) Journal
      I've nearly forgotten what traffic jams are like.
      It's like waiting in front of a traffic light. Except there are no lights, especialy no green ones. And a lot of people can't make up their mind about which direction they'll take after the lights and switch lanes accordenly.
      It's not the waiting that's so troublesome about a traffic jam, nor is the fact your boss will be very angry about you being 3 days late for work. It's the seeing other people's weird-car-habbits that's truely painful.

      Luckly there are a few ways to make it less painful:
      1) Bring your wife. Get her head in your lap. Remember to "read" a map or newspaper at the proper time. Nobody wants to see your face at that particular moment.
      2) Bring your kids! Yelling and screaming is very good to get oxygen in your system and the kicking might actually get your lower back pain to disappear. People tend to pay a lot for such a massage.
      3) Portable TV! Makes your waiting in the jam a painless affair. Might, ofcourse, make you the cause of the next traffic jam.
      4) Laptops! Pass the network cable from car to car and have a mobile LAN-party!
      5) Cellphone: Ask the number of other people in the jam and have conversations. Now you can ask what the h*ll he was thinking and discuss why he should stay the f*ck on his lane.
      6) music intruments! They call it jammin' right?
      7) Mexican wave ... with sound!
      8) strip poker with car parts! A El Cheapo car with the hood of a ferrari, now wouldn't that rock?
      9) Bring candy and beer! Instant party! Would suck if you're picked to be the sober driver. Thought bringing drunk friends home was bad? Think how bringing 12,000 drunk strangers home would be like.
      10) Disassemble your car, climb over the fence, down to the street below with as many part as you can carry. repeat as necessary. reassemble the car. Takes some time, but you'll be home quicker anyway.

    • Re: (Score:3, Funny)

      by aussie_a ( 778472 )

      Around here, the closest thing to a traffic jam is me. Even the old people think I drive too slow.
      Wow, that must be pretty embarrassing considering you live in an Amish community.

  • Field of Study (Score:4, Informative)

    by WaXHeLL ( 452463 ) on Wednesday December 27, 2006 @04:20AM (#17374740)
    There's actually a field of study for this: Traffic Analysis. Of course, this is not to be confused with all of the material out there relating to internet/network/packet analysis.

    This mainly deals with optimizing freeways and the like, based on people's behavior in traffic, and the ripple affects.
    • Which is why we get things like carpool lanes. It's the one thing I kinda like about LA. People can't impulsively jump in & out of the lane like all the rest (at most places I've seen). It keeps the quotient of people who can drive higher speeds themselves at a much better rate. To me those don't have as much to do with you having more than one person in your car. Just look at the hybrids, motorcycles, and other cars that are exempt from the two or more rules. If you are running anything but an old clun
      • Which is why we get things like carpool lanes. It's the one thing I kinda like about LA.

        Those are the lanes at the side of the road that are a few miles long and are mostly empty throughout the day, right? Or where people drive bumper-to-bumper at a barely noticeable faster rate than the folks driving bumper-to-bumper in the regular lanes?

        Personally, I think everyone in the LA area should get get over the political correctness and shitcan the idea. No one carpools (except by accident of circumstance) and

        • Re: (Score:3, Interesting)

          by micheas ( 231635 )

          . . . but I doubt there's anyone who hasn't noticed that driving through any area with moderate traffic, the lights seem to work OK, but come 4-5:00pm (or 6-7:00am), irrespective of traffic flow, the lights start turning read with increasing frequency, and traffic starts backing up. My guess is there's a BOFH version of a traffic controller in every city doing it on purpose.

          As I understand it, you are sort of correct. Lights are timed to slow cars down at rush hour to reduce the number of traffic accidents,

        • ...light rail is working in Los Angeles. What's the fastest way to get Downtown? The Red Line. 30 minutes from NoHo to Union Station. Un-freaking-believable.

          This is why when the price of gas went up, and people actually tried the Red Line and Metrolink and other parts of our old/new (most of the right-of-ways are old Pacific Electric right-of-ways) light rail infrastructure, people started talking about how nice it would be to have the Wilshire spur of the Red Line finally take its intended trip to Santa Mo

  • Roads and CSMA/CD (Score:5, Insightful)

    by rar42 ( 626382 ) <richard@caliba n . o r g .uk> on Wednesday December 27, 2006 @04:22AM (#17374750) Homepage Journal
    I'm inclined to compare roads to shared medium Ethernet. As the traffic builds up you get more 'collisions' and both systems have collision detection built-in.

    With Ethernet, as the 'traffic' builds to about 40% of the theoretical capacity, collisions become the norm and the re-tries start to overwhealm the system and it locks. With roadways, as the traffic builds to a certain limit, then awareness of potential collisions magnifies in the drivers, so reactions to situations increases and the road stalls. This is why variable speed limits work, because the road and drivers can cope with more vehicles if there is a lower maximum speed.

    • Re:Roads and CSMA/CD (Score:5, Interesting)

      by DynaSoar ( 714234 ) * on Wednesday December 27, 2006 @05:58AM (#17375062) Journal
      rar42 (626382) sez:
      > I'm inclined to compare roads to shared medium Ethernet. As the
      > traffic builds up you get more 'collisions' and both systems
      > have collision detection built-in. With Ethernet, as the 'traffic'
      > builds to about 40% of the theoretical capacity, collisions
      > become the norm

      You're pretty much completely wrong, and the last quoted line sums up why.
      Collisions are not the norm in traffic jams.

      Traffic jams happen due to the ripple effect from cumulative reaction time
      delays in response to changes in traffic. The effect accumulates until there
      is so much loss of speed that people drive closer together. Then when they
      have to react, they react more abruptly, and that causes yet a stronger ripple
      effect.

      Packets collide, cars don't. Cars change speed, packets don't.
      Well, OK, sometimes cars do collide. But it's not the collision itself that
      causes the traffic jam, it's the bottleneck in the right of way and/or the
      rubberneckers.

      If people could and would simply maintain the 2 second following distance
      no matter what speed, when the fewer traffic jams did occur, they would resolve
      themselves much more quickly. But just try telling the person 500 cars back to
      just sit still for 10 minutes. They'd probably want to punch you, and they'll
      still insist on driving stopgostopgostogostopgo despite the fact that doing so
      means they'll be doing it for several times longer than just waiting.

      90% of drivers think they're better than average.
      90% of drivers are below average drivers.
      So I give free driving lessons.
      Like braking suddenly for tailgaters.
      • Mod the parent up. He is right on the money, and reformulated by own comment

        http://science.slashdot.org/comments.pl?sid=213734 &cid=17375420 [slashdot.org]

        i have just submitted much better than myself.
      • If people could and would simply maintain the 2 second following distance
        no matter what speed, when the fewer traffic jams did occur, they would resolve
        themselves much more quickly. But just try telling the person 500 cars back to
        just sit still for 10 minutes.

        The two-second rule is unrealistic for many reasons. I broke it down in an earlier post, above, but basically two seconds at 70 MPH is a 24 car-length gap. That's 1/16th of a mile. Can you imagine the complexity that would be necessary to account for c
      • So I give free driving lessons.
        Like braking suddenly for tailgaters.

        This is why people who actually give driving lessons tell you that your job as a driver is to watch the road ahead. Let the guy behind you worry about his own driving. Without exception the worst drivers I have ever seen are the ones who are preoccupied to distraction with whatever is happening behind them.

      • Re: (Score:3, Interesting)

        by Dread_ed ( 260158 )
        "90% of drivers think they're better than average.
        90% of drivers are below average drivers.
        So I give free driving lessons.
        Like braking suddenly for tailgaters."

        For irresponsible people like you who play fast and loose with the lives of other people on the road I have a favorite past time. I like to call it "Civic Lesson 101" or YANA (Your Ass is Not Anonomyous.)

        What many people fail to recall (or do not know in the first place) is that their license plate number is linked to the public record of their auto
    • Ten cars streaming across that, that freeway, and what happens to your own personal lane? I just the other day got... a car was driven by my staff at 10 o'clock in the morning on Friday, it got in yesterday. Why? Because it got tangled up with all these things going on the freeway commercially. They want to drive vast numbers of cars on the freeway. And again, the freeway is not something you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand those tubes can b
  • ...most people just don't have a clue how to drive?

    YES! But that's not news, we have known this for over a century now...

  • On a very busy road... (Score:5, Interesting)

    by Alioth ( 221270 ) <no@spam> on Wednesday December 27, 2006 @04:24AM (#17374762) Journal
    I fly light planes. Major roads, when VFR, are very good landmarks.

    Quite often when it is very busy, you can see a standing wave in the traffic - there's an area where all the cars are stopped - but there is NO obstruction at all. The cars are filling the 'standing wave' from the back as quickly as cars at the front are leaving it - so it becomes self-sustaining.

    When the road is full to capacity, moving at 70 mph, all it takes is one person to jab their brakes ... then the drivers behind (probably following far too close) brake a bit harder, and the drivers behind them brake a bit harder still. The adjacent lanes, in seeing one lane suddenly slow go 'whoa', and someone also brakes in that lane. Pretty soon, just from one person braking a little bit - the braking has propagated down the road with greater and greater severity until one of two things happens: usually, the traffic comes to a standstill, and you get a self-sustaining standing wave of stopped traffic until the amount of traffic on the road reduces to the extent there are fewer cars joining the wave than are leaving. This can take HOURS, especially on the M6 in England. The second thing that may happen in this cascading braking severity is that someone runs into the back of the other. Then chaos ensues for most of the day.

    The other problem is lorries (large trucks) overtaking lorries with a speed differential of 0.5 mph. It takes them several minutes to get past because they are both speed limited within 0.5 mph of each other, meaning the inside two lanes are 56mph, and the outside lane is 70mph+. When a frustrated driver pulls out into the outside lane after being stuck behind a lorry for "too long", they cause one of the outside lane drivers to brake down to 56 mph quite suddenly. This can easily get the 'braking cascade' started, and before you know it - you have a standing wave traffic jam with no actual obstruction (other than the standing wave itself).

    Usually then what happens, is the opposite direction traffic, seeing the stoppage rubber necks for the possible accident. An inattentive driver looking at the other side of the road finally looks back in front and realises he's about to ram a truck in the rear and slams on the brakes. The driver behind him following far to closely has to brake even harder - and there's either a shunt or if they are lucky, ANOTHER standing wave traffic jam starts on this side of the road too.

    It's fascinating to watch from the air. Frustrating to be in when driving.

    • Re:On a very busy road... (Score:5, Interesting)

      by RotateLeftByte ( 797477 ) on Wednesday December 27, 2006 @04:40AM (#17374814)
      Some of the points are very well made.
      Just ask anyone who has been a driver at the tail end of an Army Convoy. They are either flat out of at a dead stop. The concertina effect magnifies as the number of vehicles increases. This is why smaller convoys are better.

      I was once in a lecture where this was explained. It all went down to the following
        Chaos Theory
        Queuing Theory
      and most impostantly,
        A single thing which cause on vehicle to slow down without due cause. The nthe vehicle behind has to slow and Bingo! it all starts.
      Once to get beyond a certain number of vehicles the elasticity in the queue gets to a critical size and you get the unexplained traffic jams.

      Some places try to minimise these jams by artificially reducing speed limits to reduce the elasticity but IMHO, these have limited effect.
      IMHO, the ONLY way to stop these elastic jams is to connect the vehicles together. I once saw a demo of such a thing. Oh, sorry, it is called a train...:)
      Seriously, BMW demoed a device many years ago that would allow you to get much closer to the vehicle in front but in a safe manner. I think that it is only a metter of time before there is a viable system to connect vehicles together electronically in such a way that they can be physically very close to each other in a safe manner. The driver would join such a convoy and then switch on an autopilot system and sit back and relax.

    • Re: (Score:3, Interesting)

      by steevc ( 54110 )
      It would help to cut down on the standing waves if people applied the 'join slowly, leave quickly' rule. If you see a queue ahead then slow down to give it time to move before you get there, then as soon as the road is clear accelerate away (to a safe speed). I see waves like this every day and see many people rush to join it so they have to slam on the brakes. When I get out the other side people are leaving huge gaps that slow down the escape of others.

      There's an old article on this, with animations, here [amasci.com]

      • Re:On a very busy road... (Score:5, Insightful)

        by Alioth ( 221270 ) <no@spam> on Wednesday December 27, 2006 @04:58AM (#17374884) Journal
        Oh, I do that. The thing that annoys me is when I see trouble ahead and start to slow, as soon as the tiniest gap opens, someone in an adjacent lane leaps in. It's so frustrating. Many of the problems are caused by poor 'me first' road discipline, for example, when approaching a constriction, so many drivers go right to the end and try and force their way in - and it's not helped by people not letting adjacent lanes merge in good time before the obstruction.

        The art of proper merging should be something taught to drivers and tested on the driving test.

        • Re:On a very busy road... (Score:4, Interesting)

          by mrchaotica ( 681592 ) * on Wednesday December 27, 2006 @06:04AM (#17375080)
          for example, when approaching a constriction, so many drivers go right to the end and try and force their way in - and it's not helped by people not letting adjacent lanes merge in good time before the obstruction.

          Even more, it's not helped by people letting in the drivers who go to the end. Personally, I'll let people in when they try to merge soon after noticing the obstruction. But if they try to cut in at the end, I'll ride the previous car's bumper to prevent them from getting in, and give them the finger to boot! And if that makes me a bastard, that's fine with me.

          • They may have had to wait until the end because everyone was too much of a bastard to let them in beforehand.

            • Re: (Score:3, Interesting)

              by Scratch-O-Matic ( 245992 )
              Sometimes you can tell the difference. On my commute home every day there is a one-lane offramp with a stop light at the top, and it gets backed up a half mile or so. As I approach the final merge point, most drivers who are still trying to get in have arrived at full cruising speed...an obvious attempt to "cut in line." I will ride the bumper of the car in front of me like I was on his trailer hitch to keep these jerks out. Other times, usually much further back, drivers are trying to get in late but h
          • I always drive rental cares, and I have a zero excess on them :)

            I do the exact same as you - and frankly I really could not care less if they dent the body work trying to force their way in I dont plan to move out of their way - the car isn't mine, I can't lose any no claims and it wont cost me a penny to fix.

            Its a variation of "the car with the worst body work has right of way" rule ;)

          • Re: (Score:2, Insightful)

            by berj ( 754323 )
            Umm. you may want to *read* the article at http://amasci.com/amateur/traffic/traffic1.html [amasci.com] (posted earlier). His evidence suggests that it *is* helped by people letting others in (in an effort to keep traffic flowing) and is actually *hindered* by behaviour such as yours.

          • Re:On a very busy road... (Score:4, Informative)

            by Skater ( 41976 ) on Wednesday December 27, 2006 @08:10AM (#17375548) Homepage Journal
            Uh, merging in at the end is exactly what they SHOULD be doing. Think of it as a "zipper" that closes at the end of the lane. It works out better for people in both lanes. The people that merge in early actually make the continuing lane slower for everyone.

      • Re:On a very busy road... (Score:5, Interesting)

        by MaelstromX ( 739241 ) on Wednesday December 27, 2006 @05:18AM (#17374934)
        That article is a must-read. Also interesting is this Java traffic simulator [tu-dresden.de] which demonstrates all the ways that traffic jams can form.
        • Hehe, that applet is a lot of fun to play with.

          Professor Helbing (as mentioned on that page) gave a talk at ALife X this past year. Normally, we're all about artificial biology and dynamical systems and stuff like that, so Helbing considered himself something of an outsider. But the emergent properties of traffic flow and the dynamical systems involved were actually a quite natural fit with our normal areas of research in the artificial life community.

          He talked some about vehicle traffic, but focused more

      • Re: (Score:2)

        by joshetc ( 955226 )
        It would help to cut down on the standing waves if people applied the 'join slowly, leave quickly' rule. If you see a queue ahead then slow down to give it time to move before you get there, then as soon as the road is clear accelerate away (to a safe speed). I see waves like this every day and see many people rush to join it so they have to slam on the brakes. When I get out the other side people are leaving huge gaps that slow down the escape of others.

        This is why I am a tailgater. If I'm coming out of a

    • Heh, I've noticed the same thing from the ground: the controlled-access part of GA 78 has exactly ONE curve, and that's exactly where the standing wave forms every rush hour. And you know what the worst part is? The curve is banked, so there's no legitimate reason to slow down for it!

      • Simply slowing down will not cause a traffic jam (where everyone is forced to a standstill) if everyone is driving safely. Feeling you're unable to turn at the current rate and so slowing down is safe driving. Following the person so closely you need to slow to an even larger degree is unsafe driving.
        • Feeling you're unable to turn at the current rate and so slowing down is safe driving. Following the person so closely you need to slow to an even larger degree is unsafe driving.

          I disagree. It is difficult to judge the speed of another vehicle visually under any circumstances. It is impossible to determine the rate at which another vehicle is braking -- as an AC posted above, brake lights don't give you any information except BRAKE!

          It is therefore very likely that any following car will slow to a larger de

  • Those damn butterflies are attacking America again (Score:4, Funny)

    by giafly ( 926567 ) on Wednesday December 27, 2006 @04:34AM (#17374790)
    From the article: "The 'butterfly effect' leads to a conclusion that if a butterfly flaps its wings ... that small disturbance in the chaotic motion of the atmosphere could create a chain reaction"
    America doesn't need a war on terror [slashdot.org], it needs a war on butterflies.

  • Chain reaction (Score:2, Insightful)

    by venicebeach ( 702856 )
    One problem with tracing something complex like this back to a single event that was supposedly the cause of the "chain reaction" is that the event you choose was itself caused by something. For example, from the scenario used in the article, the event that triggers everything:

    It is a clear, sunny day and the roads contain no obvious hazards that would cause problems with traffic. Traffic on this particular highway is pretty thick, but it is flowing smoothly and steadily. One of the drivers, let's say a

    • IMO someone merging unsafely is the only cause you need to go. Wait until you see someone driving unsafely, then label them the cause of the traffic jam. While it might not be scientifically accurate, it sure is just ;)

    • Seriously. (Score:3, Insightful)

      by aussersterne ( 212916 )
      Everybody is busy pointing out the "first causes" of traffic jams without noticing that every one of these causes is caused by interaction with the roads in the first place.

      The real "first cause" of traffic jams is differences in driving decisions and style. If everyone drove at 120mph, or everyone drove a 30mph, or everyone could anticipate exactly what the other driver would do before they did it, and adjust accordingly in advance, there would be no traffic jams.

      Traffic jams happen because one guy is driv

  • slow ass drivers (Score:3, Interesting)

    by mrshowtime ( 562809 ) on Wednesday December 27, 2006 @04:43AM (#17374824)
    I have lived in the cities with the worst drivers and the worst traffic and I have seen it time and time again; it's the slow dumbasses that are the real cause of majority of wrecks. It's that asshole who is going 50 in the passing lane and won't move. Or the driver is just going so slow that normal traffic rams into him, or is slowed town greatly.

    The people with really fast cars generally drive very well. After all, they don't want to smash up their fancy car.

    It's the assholes who don't care that they clogging up the passing lane who really are the cause of most accidents and traffic slowdown.

    Oh, I have noticed that traffic patterns and behaviors do vary by location. For instance in New Orleans (pre-katrina) the drivers were extremely agressive and would not let you in no matter what and pretty much there could be aliens landing on the side of the road and nobody would care or slow down. In L.A. the 405 would be backed up forever only to find out that it was slowed down because of ONE car broke down in the emergency lane, with no accident; everyone was slowing down in response to this one car on the side of the road. In San Antonio, TX, everyone is on crack and drives a Ford F450 Dually 100mph, everywhere. Not usually a problem, but the entire city of San Antonio is being redone road wise and it creates choke points almost instantly that can't be foreseen.

    • Re: (Score:3, Insightful)

      by dbIII ( 701233 )

      it's the slow dumbasses that are the real cause of majority of wrecks. It's that asshole who is going 50 in the passing lane and won't move.

      That's just what the idiot who drives too fast without paying attention and runs into them would have you believe. To make it easier to identify them they have often purchased personalised number plates identifying themeselves by name - at least in my country. If you ram into someone under ordinary conditions you are just not paying attention or do not know how to dr

      • "People who drive slowly in the wrong place may be annoying idiots - but they do not cause the accident."

        That's how the law works in Australia. If you ram a sober, licensened driver from behind your insurance company will automatically admit liability on your behalf, even if you have independent witnesses who saw the arsehole cut you off and slam on the brakes.

      • Re: (Score:2)

        by mungtor ( 306258 )
        "People who drive slowly in the wrong place may be annoying idiots - but they do not cause the accident."

        And that's just what the lazy, self absorbed twats would have you believe.

        Here's a clue: People who are driving fast are paying attention to .... Driving! Yes! They are more than likely paying attention to what is going on around them in order to figure out the fastest route through the rest of the pack. Especially if you think they are driving "aggressively", then they are definitely aware of the

        • Re: (Score:3, Insightful)

          by dbIII ( 701233 )
          Come on - you learned to stop in time when a car brakes in front of you to get your licence. Stopping in time for a car in front of you that you can see is the easy bit - it doesn't matter if they do something stupid, annoying or illegal if you are too close it is your body that can get injured so it is your own responsiblity to pay attention. Let one idiot sit in front of you being a pain instead of having two dead idiots. Cars come with horns and lights but not a battering ram even though some people d

    • Re:slow ass drivers (Score:5, Insightful)

      by beelsebob ( 529313 ) on Wednesday December 27, 2006 @06:28AM (#17375164)
      I'd agree with you partially, slow drivers getting in the way is a major cause here. But I'd suggest that it's usually actually the person in the expensive powerful car being impatient that causes the major tail backs.

      Here in Britain, I drive a small Skoda, it doesn't go too fast, but it's certainly no snail (it can do well over 100 if I really wanted to). I tend to drive down motorways at 75 or 80 mph (very naughty, I know, the speed limit is 70). The thing that I observe most often is that if I pull out to overtake some slower moving traffic (a lorry, or someone doing 70), there's usually some ass hole in a beemer, a merc or an audi comes roaring up behind me at 100mph, slams on the breaks because he realises a bit too late that there's someone driving at a sane speed, and then proceeds to tail you 5m from your bumper until you deign to move over and let the selfish twat past.

    • The people with really fast cars generally drive very well.

      Ha ha ha ha ha ha ha! Seriously, which universe did you just slide in from?

      And this is from someone who has a fast car and drives it as such.

      Every model of every car brand has bad drivers.

      Anyone else noticing the Mini Coopers have more than their share, though?

    • It's that asshole who is going 50 in the passing lane and won't move.
      I'm curious, in this example what is the speed limit?

      • Re: (Score:3, Informative)

        by Overzeetop ( 214511 )
        Well, since the OP is in LA (from the freeways he listed) - I would presume the legal limit is 65 (mph, that is), but the "free flow" of traffic is likely to be closer to 80-85 if there are no other obstructions. So, in reality the 50 the OP mentioned is probably more like 65 - practically standing still by LA standards.

        I lived outside of LA for a couple of years, and found that the OP is correct, and it applies somewhat everywhere. There is an "efficient" speed at which 90-95% of interstate highway drivers

    • Re: (Score:3, Insightful)

      by Lumpy ( 12016 )
      REally? I always saw the asshole on the pocket rocket driving in between lanes at 120mph that eats a car or two that causes most of the problems. At very least he causes the panic-able drivers to hit their brakes when a moron flies past their door 8 inches away. The slower drivers rarely cause the traffic jams it's the guys that flip out and then cut off other people because they think they are more important and thus have the right to tailgate, drive 20-30mph over the speed limit and have a little kid h
  • The phenomenon has also been called the "Spring Effect" because from the aerial view of "Choppper 4", the waves of idiocy propagating back down the line look like the expansion and compression of a spring.

  • Isn't it fairly obvious? (Score:3, Insightful)

    by eebra82 ( 907996 ) on Wednesday December 27, 2006 @04:47AM (#17374842) Homepage
    Isn't it fairly obvious why we get traffic jam?

    The only way to get consistent traffic throughput is to have cars that maintain the same speed at all times, do not switch lanes and do not turn left or right at all.

    Since all drivers have different destinations, driving techniques, cars and intentions, it is impossible to achieve this. Someone's gonna change to the other lane, delaying the people behind him who have intentions to delay the traffic in some other way, which eventually triggers traffic jam. It's a gigantic chain reaction, really.

  • How to help unjam and jam (Score:4, Insightful)

    by weave ( 48069 ) on Wednesday December 27, 2006 @05:05AM (#17374894) Journal
    This is why when in a jam the best thing for people to do is calm down and change their speed slowly to even out the speed. This means trying to predict the average speed ahead of you and do your best to maintain an even speed, even if slow. Yes, impatient drivers will move in in front of you, but they are also most likely to jump back out of in front of you in a bit too. Getting next to a truck doing the same thing helps. Pressing out the waves is what will get traffic moving again for those behind you.

    • Re: (Score:2, Insightful)

      by Keeper ( 56691 )
      You can even turn it into a bit of a game ... see how far you can travel without touching the brake.

      A few other beneficial side effects:
      * better gas mileage
      * less stress
      * less wear and tear on your brakes

      • Re: (Score:2)

        by joshetc ( 955226 )
        I used to play that game. Then I would get pissed off when I had gone multiple miles without using the brake and some random idiot was going 15 under so I would just ride his ass the rest of the way. Then when he turned off the one lane road I would do a massive burnout and speed the rest of the way home.
    • Furthermore, since your prediction of average speeds will be poorly informed and therefore wrong, the very best thing to do is to drive slower than that. Taking as a given that you're currently in a traffic jam, all the cars around you are almost certainly going too fast for the jam to clear (if there's no obstruction ahead of you, and all the cars in the jam are going slowly enough, it will clear up in the time it takes one car to drive from the back of the jam to the front at that speed - typically a minu
      • Ever notice how everybody ignores those signs and drives as fast as they can?

        No, because:

        (a) it's illegal
        (b) the police *love* picking up people for breaking these limits and are usually staked out along the stretch
        (c) half of the signs have speed cameras on them that activate along with the camera anyway.
  • that were spent to produce, sell and maintain those cars, we would be able to make endless lines of light rail-based mass transportation system that would have luxury that would put a 5 star hotel in shame ? and then we would be able to go anywhere we wanted by just leaning back, and faster ?

  • Density waves? (Score:4, Interesting)

    by niktemadur ( 793971 ) on Wednesday December 27, 2006 @05:13AM (#17374924)
    The previous theory I heard about in a documentary about traffic in major cities, said that density waves, the same phenomenon that causes many galaxies to have perfectly defined spiral arms, also cause traffic jams, which is to say, the mathematics are the same.

    As a sidenote, I once read an anecdotal story about a guy who always got stuck in the road while driving home from work, and one day he thought about how everybody's trying to get home fast yet everybody gets stuck in traffic, so he decided to experiment by driving a bit slower. After a few minutes he was amazed to find how the traffic behind him was neat and orderly, instead of the usual jumble, which implies (I emphasize: anecdotally) that the behaviour of a single car can not only create, but also avoid the creation of density waves.

    • Re: (Score:2)

      by hazem ( 472289 )
      I think you're remembering this guy's website:

      http://www.amasci.com/amateur/traffic/traffic1.htm l [amasci.com]

      If it's not, I think you'll like it anyway.

  • It's too obvious (Score:5, Funny)

    by arikb ( 106153 ) * on Wednesday December 27, 2006 @05:25AM (#17374956) Homepage
    For the longest time a friend and I have theorized about the reasons for those traffic jams. We've reached the inescapable conclusion that they are the results of a conspiracy.

    Don't go your heads a-shaking now. It's really obvious. The oil companies make a bundle of those traffic jams. Every day just before rush hour a small fleet of inconspicuous unmarked vehicles, driven by selected elderly, are leashed upon the major freeways. They are trained to drive in such a pattern that makes it impossible for other cars to bypass them. Soon enough the traffic jam forms. Millions of cars are burning precious fuel while standing still, and the oil barons go cha-ching.

    Denying it doesn't make it go away.

    -- Arik
  • and traffic jams at the SUMO [sourceforge.net] site. You can also use their open source simulation software to create your on
    traffic scenarios. I have always seen the creation of a traffic jam as a transition from a high density high flow state meta stable state to a high density low flow state. This can be expressed with a lambda shape curve in a density-flow diagram. The cause for exiting the meta stable state can be a
    small disturbance, sometimes simulated by a random factor in CA traffic models, e.g. some guy braking with
  • All the tailgating idiots who falsely believe that they can drive safely less then two seconds behind the car in front of them are the real cause of this sort of delay.

    The fool who taps his brakes is merely the trigger.

  • Old, old, incredibly old news (Score:5, Interesting)

    by deblau ( 68023 ) <slashdot.25.flickboy@spamgourmet.com> on Wednesday December 27, 2006 @05:44AM (#17375024) Journal
    See this Science Hobbyist article [amasci.com] from January 1998. It's long and detailed, and suggests practical steps individual drivers can take for breaking up (or causing!) traffic jams. Yes, dear readers, this is a nine-year-old dupe.

  • Valid reason, but not the main one (Score:4, Interesting)

    by mapkinase ( 958129 ) on Wednesday December 27, 2006 @07:46AM (#17375420) Homepage Journal
    I can testify that this is not the most popular reason of traffic jam, because this is not the most common disruptive behavior. Think: why the situation was happening? It is not because just one driver wanted to change the lane, this is because many drivers wanted to do that and one of them was too impatient. That takes off the load of one individual and brings it upon the condition of why the lane was slow?

    Most likely the lane was slower because (a) there was a high-inertia-mass truck in front of you or (b) sloppy driver (undercaffeinated, grandma, or just plain unexperienced driver).

    This condition could not be helped. The critical condition of the stand-still or bumper-to-bumper traffic jam is caused by concentration of cars increasing certain threshold level. The main factor in this criticality is the distance between cars. How many of us actually follow three-second rule? The tail-gating leads to the high probability of the scenario when the car in front of you breaks and you will be forced to break with the HIGHER deceleration. That leads to lesser control of the final steady speed achieved at the end of the process of deceleration. Needless to say that the chain reaction will continue all the way back with increasing decelaration and decreasing final speeds of deceleration.

    The solution to the traffic jam problem is trying to smooth traffic even at very low speeds. To do that we need stricter laws regulating tailgating. It needs to be automatic, the cars should be equipped with automatic sensors, all the entrances to the freeways/highways should be regulated by traffic lights.

    Again: the problem with traffic jam is the criticality at certain speed. The only way to lessen this criticality is to increase distance between cars.

    The other good way of easing traffic jams is complete abandonment of upper speed limit. That will increase the efficency of the traffic arteries.

    Together, tougher tailgating regulation and absence of speed limit, will help the traffic jam situation in the country.

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