Buses represent the most widely used transit technology. Virtually every city in the world that has
transit service, operates buses. Large cities with rail transit also operate extensive bus networks,
usually on lines with lower passenger volumes or as feeders to rail lines.
Bus service is easy to introduce or modify: basic service requires only purchase of vehicles, garage
and maintenance facilities, and organization of service. Stops along the lines can be simple.
Therefore, buses represent the most economical transit mode for lightly traveled lines. This
flexibility of bus routes is an advantage for any necessary changes, but it is a disadvantage for major
bus lines: they lack permanence, efficiency in carrying heavy passenger volumes, and image of
permanent, physically fixed routes desired by passengers.
Compared to paratransit modes, bus transit is very labor-efficient: one driver operates a vehicle with
capacity of 50-150 spaces. Compared to rail transit, buses are labor-intensive and have no economy
of scale: on heavily traveled lines for every additional 40-120 passengers, one bus and one driver
must be added to service.