Explanation of a traffic jam sought

Discussion in 'Human Science' started by mtf, Jul 29, 2016.

  1. mtf Banned Banned

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    How come this happens?

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    https://linkbeef.com/19-photos-that-will-make-you-wonder-whats-wrong-with-the-world/


    The intersection seems to be one with semaphores, it's not a roundabout.
    The traffic has come to a complete halt, it's in deadlock.

    I'm posting this in Human science, because the problem doesn't seem to be a tehcnological one, but a human one: People insisting in their right of way, no matter what, even if this leads to a complete halt of all traffic so that nobody can move in their originally desired direction.

    Technically, the solution is simple enough: The drivers in the vehicles at the outer edges of the jam would need to move aside or drive away, make room for the traffic to begin moving again. (Instead, it looks like they are all waiting for the traffic police to arrive to make order.)

    But making room like that seems to be too much of a sacrifice to make. How come?
     
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  3. The God Valued Senior Member

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    It is the stupendous skill of human beings to convert the win-win situation into loss-loss situation for all involved on the first available opportunity.
     
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  5. iceaura Valued Senior Member

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    That's one lousy intersection design. The problem is that drivers can't tell whether they can get through until they are in it, and just one sufficiently large vehicle getting stopped briefly across the street (like that green and white bus) can jam the whole thing.
     
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  7. sculptor Valued Senior Member

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    The above is also known as "gridlock", when everyone wants to get into the intersection. "The hurrier I go, the behinder I get".
    And, then.
    Follows the cacophony of incessant horn honking.
     
  8. el es Registered Senior Member

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  9. mtf Banned Banned

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    Thanks for a bigger picture of it!
     
  10. mtf Banned Banned

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    The interesction appears to be one with semaphores, and as long as they are working and people respect traffic rules, things should be fine. A roundabout or a turbo roundabout would easily solve the problem, too.

    I used to drive a lot in mountaneous regions in Europe. Sometimes, the roads there are so narrow that two vehicles cannot pass eachother; there's a steep slope on one side of the road and an abyss on the other. There are niches on the side of the road as the terrain permits, so that if two drivers are to pass eachother, one has to drive into that niche. Intersections are sometimes so narrow that one has to forego usual traffic rules and just see what will work out. And yet on these roads, there is traffic (albeit not so much) of cars, tractors, trucks, and even buses and somehow we managed to drive safely. Driving in such conditions can make one a different kind of driver.
     
  11. spidergoat Valued Senior Member

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    That's what traffic cops are for. Or traffic lights. What the hell is a semaphore?
     
  12. mtf Banned Banned

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    semaphore = traffic lights
     
  13. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    I'd say there's too many cars.
     
  14. sculptor Valued Senior Member

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    Or:
    Traffic jams are often caused by the stop-start driving typical in aggressive drivers Photo: ALAMY

    While the underlying cause of a jam might be an accident, a bottleneck, or drivers simply changing lanes on busy roads, it is how the drivers react in the cars behind that cause traffic to slow to a halt.

    Researchers say aggressive motorists, who drive too fast and too close to the vehicle in front, or timid motorists, who leave too big a gap, send a "wave of deceleration" backwards down the road until traffic grinds to a stop.

    Such behavior leads to the stop-start traffic jams which infuriate motorists.

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    Too Many Cars Cause Traffic Jams

    A Japanese team has found the underlying cause of traffic jams when there is no obvious reason for the delay.

    Many traffic jams leave drivers baffled as they finally reach the end of a tail-back to find no visible cause. An accident? Construction work? A bottleneck? No, just too much traffic, says a team led by Prof Yuki Sugiyama of Nagoya University, who has spent more than a decade puzzling over the problem.

    In the New Journal of Physics a study by his group explains why we're occasionally caught in jams for no obvious reason.

    The real origin of the snarl up often has nothing to do with obvious obstructions such as accidents or construction work but is simply the result of there being too many cars.

    from: http://www.batoautomoto.com/Aggressive-and-Timid-Drivers-Cause-Traffic-Jams.asp
     
  15. mtf Banned Banned

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    But that doesn't explain traffic jams in intersections. In the above picture, the situation seems to could only have come about because some drivers didn't respect traffic rules. It is understandable that in heavy traffic, there would be long lines before the intersection, but not in it; unless the line of waiting cars extends from one intersection to another.
     
  16. billvon Valued Senior Member

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    That happens often in big cities. "Don't block the intersection" is a common sign in places like that. All it takes is a few people not noticing and you can get the sort of gridlock you see above.
     
  17. mtf Banned Banned

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    There needn't be signs for that: it's a traffic rule, at least in Europe. You're not supposed to drive into an intersection unless you have green and there's room; otherwise, you have to wait before the full line.
     
  18. iceaura Valued Senior Member

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    It's a problem design, that would require sophisticated and quite intrusive semaphore timing to have any chance of remaining clear. One sufficiently large vehicle (or two smaller) even temporarily unable to clear the intersection in any of four directions - like that bus - can jam all four roads. This is partly because the median is too narrow to "hide" a vehicle in - visually, an ordinary driver would have to predict the behavior of both the semaphore and the traffic in the oncoming lanes, clear across the eight lanes and a ways down the four facing lanes on the other side, to be able to determine whether or not they could clear an intersection in which, at the moment of decision, they have the light and traffic is moving ok.

    That's asking too much. This is a four road double intersection masquerading as a two road single intersection. If you drew this with a crayon on a napkin you'd see the problem immediately.
    But you have to be able to determine that, while in motion and in traffic.

    I'll bet a large number of AI cars without specific software for handling that specific kind of intersection - just driving on regular rules - would jam that intersection.

    The only hope now would be to manage all four incoming roads as separate green lights, and pinwheel the sequence clockwise ("right hand right of way" like in the old days) with "4 red" intervals sufficiently long to clear the intersection every second green, in timing with the lights downstream.
     
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  19. sculptor Valued Senior Member

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    Amen
     
  20. mtf Banned Banned

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    In Europe, wherever possible, they make roundabouts and turbo roundabouts.
     
  21. billvon Valued Senior Member

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    Agreed. But people often forget.
     
  22. mtf Banned Banned

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    People forget traffic rules ... yes ... sad but true.
     
  23. spidergoat Valued Senior Member

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    The problem is too little enforcement of the lights. A red light camera would fix that up soon enough. I hate the things, and they can be overused, but it really makes people pay attention. I almost caused an accident the other day stopping for a yellow, due to a ticket I got by mail from a camera. I like to practice emergency braking anyway, it's almost as exciting as acceleration.
     

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