I'm about to take a depressingly long bus ride in Latin America and am wondering what the longest scheduled public bus ride in the world is.

By 'scheduled' I mean for there to be a regularly operating connection between the start and destination locations, without switching busses. Besides they no longer seem to operate, this would disqualify something like oz-bus.

By 'longest' I'm tending to favour distance over duration, though either way, circular repetitive journeys would obviously be excluded.