The Civilian Bus is a very lightweight, very vulnerable transport vehicle with unimpressive performance.
It is found driving around Eos and Oasis, often full of colonists, though occasionally the Red Faction will provide one for Alec Mason to drive several colonists to the site of a Red Faction Raid with. The Civilian Bus is very fragile and if a civilian driver panics, they stand a good chance of destroying the bus themselves. It is a very poor choice for any Red Faction activities and Alec Mason may well be safer on foot than operating this vehicle.
Nevertheless, it is a common site on the streets of Oasis and Eos, presumably because it is cheap and adequately hauls a number of persons without difficulty.