[ChrisFoster]

It strikes me that even with a perfectly regular starting schedule, buses might clump together in time because the schedule is probably dynamically unstable. To explain, picking up passengers from a stop costs time and a long time between buses implies a high probability that passengers will be waiting at a given stop. This further adding to the delay and shortens the time to the next bus in the schedule.

I'm sure drivers try to actively manage this, but if they didn't I suspect the system would naturally evolve toward pairs of buses leapfrogging each other on long routes.

[jobigoud]

I think another confusing factor about that specific example is that bus shouldn't ever start before their schedule. Otherwise you run the risk of a bunch of people missing their bus even though they showed up on time. I think bus, trains and planes can only be late.

For example this is an article about a Japanese Train company issuing a public apology for departing 20 seconds early. https://www.bbc.com/news/world-asia-42009839