The book I plugged before, Walkable City, said that a successful public transportation system should run at least every ten minutes. If people have to wait more than ten minutes for whatever they’re waiting for (bus, subway, etc.), then they’re more likely to decide to just drive to their destination. This is obviously more true for places with an entrenched driving culture, but anyway, the book said that almost no municipality wanting to start up a public transportation system wanted to pay to have it run every ten minutes, because that would mean having more buses/trains and hiring more drivers. So, instead, most of them decided that a 15-20 minute wait was their goal. And then, when the public transit system failed, the municipality would be like, “See?! People just won’t use public transportation! :-(” And part of the book’s argument was, well, they are indeed much less likely to use *bad* public transportation, yes.