As I commented elsewhere, passing is not always an option in Pittsburgh.

> 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".

It doesn't have to be always an option. The bunch is moving so it is enough if every third stop offers an overtaking opportunity.

But yes, that going against the flow doesn't make overtakings any easier.

Another potential solution during rush hour would be route splitting - each alternating bus on the route is assigned to stop at even/odd stops (e.g. bus 1 stops at 1/3/5.., bus 2 stop at 2/4/6.., 3 at 1/3/5..). This assumes that the extra walking distance between stops isn't too unacceptable (and has some issues for people with disabilities).

Socialising the idea to the passengers is also probably difficult.

They already do that in NYC. It doesn’t help because the following stops are full of extra passengers and the crowds on the buses quickly equalize while they remain bunched.

I didn't state it that clear, but I am well aware that adding overtaking to the equation doesn't solve the bunching problem .

But the bunching itself is not a problem. The problems are the effects it causes like:

1. crowded busses

2. arrival delays

Overtanking has a major impact on the first effect as you have stated too, the 'crowds on the buses quickly equalize'. The impact on the second effect depends on some other parameters. If all busses are crowded there will be no effect at all, but if only a few busses are crowded (the front busses) and the busses behind them are empty, there can be a positive effect on the arrival delays too (the worst case drop off time will be lower).

So I would not say 'it does not help' as it certainly decreases the negative effects.

I suspect this isn’t as easy as you think. Where I am (Seattle) an empty bus overtaking a full one isn’t really feasible given traffic and lane size considerations.

Well, maybe you should consider banning cars from the city center then. ;-)

I mean, where I live, busses manage to overtake in a one lane for each direction scenario (which is theoretically complicated, but works out in practice as traffics lights can give you chances to use the opposite lane). Nevertheless, what is important is that the front bus waits until the busses behind him have taken the lead. Otherwise there will be very few opportunities to safely overtake the front bus.

I don’t think banning cars would do much, to be honest. Banning cars might actually exacerbate the problem as the folks who would otherwise drive out of convenience now take the bus. Structurally, on many streets there literally just isn’t another lane available for an empty bus to overtake a full one. Getting rid of more cars, while a noble goal imo, won’t fix that.