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Comment by smegel | Hacker News Reader

Is it just me, or did it not actually explain why:

> Bus bunching happens because, if a bus gets delayed, then there will be more people waiting at the next stop than anticipated. The extra passengers' boarding time makes the bus even later, and so on in a vicious cycle.

OK, so I get that buses get delayed. And even more delayed. But why buses "bunch" up and arrive at the same time doesn't seem to be explained anywhere.

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This doesn't even seem like an accurate simulation, if bus 1 is unloading/loading at a bus stop and bus 2 catches it, bus 2 waits for bus 1. This makes sense in the context of the website because buses always drop off/pick up passengers when they get to a bus stop. But that isn't how it works in real life, if bus 2 doesn't have to drop off someone while bus 1 is at the stop it will just leapfrog past it.

The fact that busses don't overtake each other seems to be the reason the bunching happens, as soon as the front bus starts slowing down a little it's inevitable bus 2 will catch it and then the situation can't be fixed.

Because as the lead bus gets filled, the following bus has fewer and fewer people to pick up, so it speeds up until it catches the lead bus, which is running later and later due to the passengers overloading, who turned up early for the later bus. The lead bus can't be passed by the following bus, so they bunch.

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