When buses are running frequently and the weather is good and the traffic isn’t bad, ProximiT works fine enough for main bus routes, though I imagine that’s more a function of the probability of it being accurate give a higher density of buses. However, if it isn’t rush hour, ProximiT is near useless for buses. I have spent 40 minutes at a bus stop that was perpetually 2-3 minutes away according to this app’s predictions. Also, unlike the Nextbus app, which is unfortunately no longer supported for Boston transportation, this app does not show you where the buses are on the map, so it’s impossible to make your own best guess. In short, the bus arrival time estimates are wildly unreliable and ProximiT is only marginally useful.