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Science

Think Airports Are Chaotic? You Are Right. 24

Posted by michael
from the entropy-increases dept.
jonfromspace writes "Nature is running a brief, but interesting article on Chaos Theory, (as opposed to KAOS) and how it relates to that damn airport shutle service. I knew there was no way to predict arrival times with any degree of certainty. >Also worth a read is this paper on applying Chaos Theory to fisheries management."
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Think Airports Are Chaotic? You Are Right.

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  • by The Cydonian (603441) on Tuesday September 30, 2003 @10:53PM (#7100379) Homepage Journal
    but the Nature article talks about airport bus frequencies, not airports per se.

    The distinction is important though; when you talk of 'chaotic airports', you're talking of the entire system as a whole:- luggage screening, plane scheduling, passenger movements etc. Dr Nagatani's paper talks about none of these; it merely suggests that the reason shuttle buses (and elevators) appear to come together, or none at all, is chaos.

    I can understand where Dr Nagatani is coming from on explaining bus (and elevator) frequencies, but am intrigued by why it is a "problem" (as in user-level problem, not physics problem, if you get what I mean) in the first place. Okay, so the bus comes at 09:23 and not 09:15... big deal. It is merely a matter of managing passenger perceptions.

    More to the point, can anyone explain why this would be inefficient for the system as a whole?

    • by Dannon (142147) on Tuesday September 30, 2003 @11:41PM (#7100668) Journal
      More to the point, can anyone explain why this would be inefficient for the system as a whole?

      Managing bus services isn't my line of work, but I can give it a shot.

      For starters, I'm guessing the "bunching problem" would lead to inefficiencies, for one thing, in passenger loading: The 9:15 bus and the 9:20 bus are both bound along the same route. The first bus is early, the second bus is late... meaning that the first bus ends up overcrowded (grouchy customers), and the second bus departs from the stop under capacity (same amount of fuel spent whether carrying one passenger or twenty).

      There's also the problem of limited resources. Say you've got more shuttle busses than shuttle bus loading spaces at a certain airport. I look at the international airport in my town, and I see shuttles for several park-and-ride services, countless conference centers, every high-class hotel in several hours' drive, not to mention the usual collection of Grayhound, metro transit authority, touring companies, and so on. The optimal situation would have an empty space ready for each bus as it arrives, so the passengers wouldn't have to wait to disembark. As things get more chaotic, though, they get less optimal. That's all there is to it.

      Talking about changing passenger perceptions, though, reminded me.... My page-a-day calendar at work had a bit about how the London rail service managed to fix a problem with chronically late trains without spending any money at all. They simply redefined "on time" to include any train up to an hour late. Problem solved, right?
    • Perhaps this could be extended to other services; Douglas Adams once referred to the Greek ferry timetables as "the greatest work of fiction known to man", and others have drawn the same parallel to British Rail timetables...
      • That was in Dirk Gently's Holistic Detective Agency wasn't it? :-)
      • Its also a matter of management and the drivers.
        If the manangement is lose, and the drivers don't care. Then the drivers will skip stops or drive faster, arriving early, leaving early- so that they get their round done faster and go home sooner.

        Management needs to understand where the people will be and at what times. Then they need to make more busses available at that time. Stick a GPS on a few random busses, and the drivers will fall in line. Maybe even mount video cameras at major bus stops to moni
    • Getting around in an airport today can waste huge amoutns of time. For example I can get to the local airport 20 minutes before departure and still get on the plane if a large number of other factors are right such as its not the morning or evening rush and there normal gate is being used so I don't have to count on a shuttle and no group is on strike. Other times I may need to be there two hours before hand and in some airports 4 hours is pushing it.

      Of course the solution to that nonsense would be put t
  • by Anonymous Coward
    I remember during the late 1970s you could sometimes find OJ Simpson flying through the airport like Superman.
  • Look at the publication histogram at the bottom of this ResearchIndex citation query for 'chaos' [nec.com]
  • In other news... (Score:2, Insightful)

    by Anonymous Coward
    Think slashdot moderations are chaotic? You are right!
  • Bunching buses (Score:5, Insightful)

    by driptray (187357) on Wednesday October 01, 2003 @01:31AM (#7101159)

    Regular bus commuters might be familar with the phenomenon where buses tend to come in groups - often in threes. For example, instead of 1 bus every 10 minutes you get 3 every 30 minutes.

    Why? My theory is that as the system becomes crowded, a bus will be delayed by having to pick up and drop off extra passengers. As it gets slower, two things happen:

    1. People have to wait longer at the bus stops. This causes the first bus to have to deal with a greater number of passengers, and makes the bus slow down even more.

    2. The bus behind it starts to catch up. This occurs partly due to the slower speed of the first bus, but is amplified by the fact that as the second bus gets closer, there will be less passengers waiting at the stops, thus allowing the second bus to travel even faster.

    The solution would be for the first bus to deliberately miss stops wherever possible so as to keep some distance between it and the next bus, and to even up the passenger load.

    • In fact there is supposed to be a paper about this though I have been unable to locate it.

      One of the surprising conclusions is that on some routes the best time to arrive is just as a bus is leaving. There are a number of reasons for this. One is that the departing bus has reduced the queue length at the bus stop so you are more likely to get on the next bus. Another is that if the buses tend to group, in groups >= 3, if a bus is leaving the probability that it is not the last bus in the group is >0.5

    • Re:Bunching buses (Score:3, Interesting)

      by wind (94988)
      At least where I live (Brighton, UK) this appears to be exactly what the bus drivers do at peak times, at least up in the hinterlands of the residential areas. I can't tell you how many times I've waited an extra 10 minutes for the bus, only to have it speed past me with bus driver sternly shaking his head. Then the next bus comes a minute later.

      Thing is, it doesn't appear to help. Usually afterwards the buses still end up next to each other. Understanding that it's due to being a chaotic system probably w
    • Re:Bunching buses (Score:1, Interesting)

      by Anonymous Coward
      I live in Minneapolis, MN and the busses here regulate this actually. What they do is, if they are too far ahead of schedule, they have a computer on board that will tell the drivers to pull over and wait for some amount of time (provided they're in a place they can do this). The busses all have some type of GPS on board too because it will alert the drivers if they are not on a specified route. If they are behind schedule I dont know what they do in thta instance. I've never had a bus more that 5min la
    • Re:Bunching buses (Score:2, Interesting)

      by p3d0 (42270)
      In Toronto, I have seen TTC busses leapfrog each other, presumably for exactly this reason.
    • I have this book from Amazon [amazon.com]. It is actually quite a good book which even covers this topic. This particular problem is even in the title!

      If you like books on recreational mathematics without being too burdened down in homework, this one is worth a read.
  • This kind of reminds me of the book, where the starship Bistromath operated off of the times and operations in an Italian restaurant.
  • The abstract is here [aip.org] with links to the full article for subscribers.

    I don't see anything unexpected in the report. In particular the statement "When the loading parameter is larger than a threshold value, each bus carries a full load of passengers throughout its trip" means "if more passengers want to use the service than the buses can carry, then the buses will be full and the queues of passengers will get longer over time". This is a standard result of queuing theory as well as being common sense.

  • Ok, I have to say it...

    My airport has always been a Chaotic Evil Thief.

    my apologies to D&D

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