A bus may have only a couple of passengers, especially at the beginning or end of its route. But let's also take fuel efficiency into account.
If there's one person on a bus because that person cannot or doesn't want to drive, the bus is succeeding.
I read a study once on the fuel efficiency of various types of commuter vehicles (car, bus, train) on a per person basis and the number of people needed riding public transit to match the "efficiency" of cars is shockingly low. A bus needs to carry like 3-4 people to be fuel efficient, and trains require 2-3 per train car. Both often carry two dozen or more during peak hours, more than justifying any perceived requirements for efficiency for the train or bus to provide service the entire day.














