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Comment by paulsutter | Hacker News Reader

Naive question: when buses are bunching, can't the front bus skip stops that are not needed for dropoffs? (the driver would have to announce that passengers need to request their stops of course).

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Ah this is an interesting idea. Passengers already have to request when they want to get off. I'm assuming you mean if no one wants to get off, a bunched up bus skips a stop because a bus behind it says "I'm behind you, I'll take this stop."

That would mostly work, but the problem in Pittsburgh at least is the bus bunching happens between related but not quite identical routes. For example, the 61A, 61B, 61C, and 61D all run down Forbes Ave, and frequently get bunched there. But then later in their routes, they fork: two go one direction, and two go the other direction. For many passengers, it doesn't matter which one they take. But for other passengers, it has to be a 61A etc.

Technically it isn’t bunching if it is for different routes. The standard industry definition for bunching as I understand it is when multiple buses for the same route are bunched up.

As is hinted at by the paper, bunching is generally caused by factors such as traffic which makes it hard to actually eliminate. Transit agencies have tried various solutions to the problem and it is very much a work in progress. One thing I have noticed is that transit agencies tend to have sub-optimal data for their service so they tend to be slow at fixing scheduling related issues.

Ah, maybe that’s the formal definition. But it’s still frustrating to be at a bus waiting for a late bus and then see a 61A, B, and C all in a line, knowing that any of them will get you to dinner :P

The real issue is that the BACK bus needs to pass the front bus and move ahead a couple of stops.

Pittsburgh, however, as an unusual misfeature in that the single bus lane goes the wrong way against one way traffic (3 lanes of cars going one way--1 lane of bus going the opposite) for a non-trivial amount of length flagged as "hotspots".

This means that while automobile drivers using the bus lane is a self-correcting problem, a bus cannot pass another bus in those areas.

(I call the wrong way bus lane a "misfeature" because it regularly results in out-of-towners winding up dead because they didn't look both directions on a "one way" street. This is particularly tragic when the out-of-towner is someone who is visiting Children's Hospital because their child is being treated for some very aggressive disease.)

I suspect the odds that there is no one that wants to alight at a particular stop on a fully crowded bus are rather slim, both mathematically and anecdotally.

Do they really stop everywhere unconditionally? In the UK almost all stops are by request, for both boarding and alighting.

As another comment noted, even if the stops aren’t unconditional the probability that no one will pull the cord for any particular stop on a crowded bus is near zero.

But then it's a simple case of the front bus not letting anyone on (only opens it's rear doors). Everyone then gets on the 2nd bus. The people become spread out between the buses and the probability of not always needing to stop increases. That does obviously only work where your bus design allows it and also to some extent, your drivers being wise to it.

Controlling which doors open as dependent on how full the route is and how bunched the buses are is just going to confuse passengers and make for a horrible rider experience. I sympathize with the idea though, as veteran riders know to move to the back as the bus nears your stop.

I mentioned it as it's what sometimes happens in London when the bus is very crowded. They do it because at the point it makes sense the rider experience is already horrible. For most buses it is front doors for getting on and rear (middle) for off. It's already independently controlled so it is not extra complication. But I do appreciate other places don't have the same system.

And the passengers not being idiots who feel entitled to exit through whichever door is nearer their ultimate destination. Also the infuriated passengers who’ve been waiting for half an hour or more not taking bricks and bats to the driver’s window.

This assumes all stops are equally popular, but that's very unlikely.

I suspect a lot of bunching is caused by buses having to perform complicated manoeuvres around car traffic because of poor stop positioning. In Barcelona what many lines do is skip stops right before left-hand turns (the line isn't even listed at that stop). This way the bus can switch lanes well ahead of time and avoid having to wait for traffic to go though all lanes. This works because most lines stop every two blocks, so you never have to walk too far for the next stop.

The challenge is arranging for those at the stop to understand what's going on. It is disconcerting to have the #75 bus go past without stopping when you're waiting for a #75 bus.

If there's a bus 250m behind it that confusion will not be long lived.

Trivially solved if the bus has a digital display - just show “out of service” in the front bus once bunching starts to occur.

Someone I know was standing at a bus stop on the phone to me, when the expected bus sailed straight past without stopping. This person then started running after the bus and shouting, trying to get its attention to make it stop. This meant that when the next bus came along 1 minute later, they were not at a bus stop, and that one went straight past as well. All while I was trying to tell them that the only reason a bus would go straight past is if there is another one just behind it, and to just sit tight at the bus stop. He/she/it was not in the slightest bit amused.

I have seen this happen sometimes, but there are always passengers who forget to signal and then run to the front shouting for the driver to stop. Not worth the hassle.

Aside from infuriating the waiting passengers at those stops... my experience is that a packed bus will have someone getting off at every single stop anyway.

Yes, he can. But here is the problem: the front bus has most likely the most passengers and therefore the lowest chance of skipping a stop ;-)

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