High occupancy vehicles have to drive fixed routes, and will have lower occupancy than a fleet of smaller vehicles that can provide exactly the number of seats

High occupancy vehicles have to drive fixed routes, and will have lower occupancy than a fleet of smaller vehicles that can provide exactly the number of seats needed. This means they'll only be useful on high traffic corridors, like between urban centers. But they compete with light rail for that use. I expect they to be squeezed mostly out of existence from both sides by rail and autonomous cars. They'll lose on cost, efficiency, and convenience to one or the other in almost every category of travel.