That may be true in some cities, and not true in others. As a car driver in a big city, I've rarely seen a bus pass another bus, but I have seen buses all bunch

That may be true in some cities, and not true in others. As a car driver in a big city, I've rarely seen a bus pass another bus, but I have seen buses all bunched together. I suspect there is no incentive for a bus driver to pass another bus. He's not the one in a rush to get anywhere.