Comment by lavelganzu

There is a downside of making buses free, similar to the experience of cities which stopped enforcing "turnstile hopping" for trains, which is that it attracts a small number of hostile and malicious riders. An advantage of treating transit as a public good means this downside becomes an empirical question, not a moral one: Which approach leads to more ridership? In some cases, enforcing fares leads to more ridership by increasing safety and decreasing the amount of time spent cleaning up befouled surfaces.