Most active commenters

    ←back to thread

    The waiting time paradox: why is my bus always late? (2018)

    (jakevdp.github.io)
    219 points skadamat | 12 comments | 20 Aug 24 13:55 UTC | HN request time: 0s | source | bottom
    Show context
    rjmunro ◴[20 Aug 24 17:11 UTC] No.41301868[source]▶
    There's another thing that happens with busses that makes it worse.

    The further behind the previous bus a bus is, the more people will arrive at the bus stop. The more people there are at the stop, the longer the bus has to spend picking them all up and selling them tickets etc. Therefore the delayed bus will tend to experience more delay. The bus behind them will have less people to pick up, so it will spend a shorter time at stops and tend to catch up with the first bus, so the two busses are dragged towards each other.

    replies(15): >>41302070 #>>41302114 #>>41302390 #>>41302468 #>>41302658 #>>41302680 #>>41302728 #>>41302736 #>>41302776 #>>41302981 #>>41303563 #>>41304355 #>>41304721 #>>41305067 #>>41329626 #
    1. bhuber ◴[20 Aug 24 18:35 UTC] No.41302680[source]▶
    This phenomenon consistently happened to my college bus system, but on an even worse scale. The main bus line did a loop around campus, which took ~20 min to complete and buses scheduled every 5 minutes. In reality, you got a caravan of 4 busses arriving every 20 minutes, with the first one totally full and the last practically empty.
    replies(2): >>41302894 #>>41305480 #
    2. theluketaylor ◴[20 Aug 24 19:00 UTC] No.41302894[source]▶
    When I was a teen in Calgary the transit agency was really good at dealing with issues like this during peak periods. They would pair or triple busses together and alternate stops. If someone requested the stop the drivers would radio to coordinate. Sometimes both buses would have a requested stop, but they would work together so only one bus allowed new riders on. The non-loading bus would quickly drop off passengers and leave while the other stayed behind to handle new riders. Nearly all the stops had dedicated out of traffic space for the bus, so the leap-frog maneuver was really simple. A small amount of low cost infrastructure and some operational cooperation enabled much better service.
    replies(1): >>41303495 #
    3. a_e_k ◴[20 Aug 24 20:01 UTC] No.41303495[source]▶
    Another simple strategy that I've seen is simply for the loaded bus to allow the empty bus to overtake it and go on ahead (and just stay ahead).
    replies(1): >>41304186 #
    4. pc86 ◴[20 Aug 24 21:18 UTC] No.41304186{3}[source]▶
    That sounds identical to what the Calgary busses do? You'd still need coordination between the busses to know when the loaded bus "wants" the empty one to overtake it.
    replies(3): >>41304475 #>>41304914 #>>41306681 #
    5. hobo_in_library ◴[20 Aug 24 21:51 UTC] No.41304475{4}[source]▶
    The driver in the front sticks his hand out the window and waves to the one in the back
    6. a_e_k ◴[20 Aug 24 22:52 UTC] No.41304914{4}[source]▶
    The difference is that it was a one-and-done thing rather than leapfrogging back and forth as it sounds like `theluketaylor` was describing.

    And yes, the drivers would coordinate. (I've sometimes seen it done with a brief honk for attention followed by a hand wave.)

    7. rvb ◴[21 Aug 24 00:21 UTC] No.41305480[source]▶
    This phenomenon is called "bus bunching". My friends, two profs from Georgia Tech and UChicago, came up with one solution for it. They wrote a paper about their solution[1], and then built a startup that has successfully implemented it at a bunch of places[2].

    [1]: [A self-coördinating bus route to resist bus bunching](https://doi.org/10.1016%2Fj.trb.2011.11.001)

    [2]: [NAU’s new bus system makes for shorter wait times for riders](https://news.nau.edu/nau-bus-schedules/)

    replies(1): >>41306970 #
    8. mulmen ◴[21 Aug 24 04:05 UTC] No.41306681{4}[source]▶
    Why does the loaded bus’ preference matter? If you see a bus stopped ahead of you with the same route number and nobody requested that stop then just continue.
    9. occz ◴[21 Aug 24 05:12 UTC] No.41306970[source]▶
    That's interesting.

    Looking at the second link, it seems they implement it by having the buses pause at certain points. Does it do that with riders onboard? That seems like it could be a deterioration in experience for those riders that are on the bus pausing.

    replies(3): >>41307012 #>>41308210 #>>41314776 #
    10. RF_Savage ◴[21 Aug 24 05:22 UTC] No.41307012{3}[source]▶
    It does sometimes feel stupid for the bus to idle at the stop for 1-5 minutes, but on the flipside they are in time on the dot at the stop.
    11. was_a_dev ◴[21 Aug 24 08:47 UTC] No.41308210{3}[source]▶
    I guess the reality is, as a passenger, you either wait several minutes on the bus at a stop mid-route. Or you wait much longer at a bus stop in a crowd waiting for four buses to show up.
    12. rvb ◴[21 Aug 24 22:20 UTC] No.41314776{3}[source]▶
    When possible, they pick "control points" at places where there are usually no passengers on board — for example, the ends of a linear route, or the bus depot.

    But otherwise, they have a bunch of optimizations to spread the pauses out so they aren't too jarring. They also display the timer prominently so that riders are aware of what's going on.

    In practice, riders seem happy with the tradeoff, since it has resulted in overall lower times to get from point A to point B.