Big Vehicle vs Small Vehicle Transit

Prior to the invention of the steam engine, all peoplemoving was done with small vehicles.  Horses, small wagons, your own two feet, etc.  The steam engine and its internal combustion relatives made it possible to go much faster, and to carry more people at once.   Until about 1910, most of these machines required a highly expert operator, who was expensive, so there were economies to be gained by going with bigger vehicles.  Even the earliest streetcars, which were powered by a horse and driven by a person with an expertise that was commonplace at the time, were larger than the normal vehicles used to move people and goods.  Consequently our notion of Mass Transit came to be affiliated with big vehicles.  To be economical, big vehicles and their drivers must operate on a schedule, on a predictable route.  Nearly all go back and forth on this route.  This is called line-haul transit.  Trains, trolleys, monorails, buses etc., all use the biggest vehicle practical and operate on a line-haul route on a schedule, even when the driver is a computer.

Meanwhile, pedestrians, horses and eventually bicycles and automobiles move far more people.  These are unscheduled, take their rider(s) from one point to another and nowhere else, and are operated by one of their riders.  Because their operator is unpaid, an automobile's actual operating costs per passenger-mile, when everything is factor in--road construction costs, vehicle costs, etc., are about the same as the cost of a bus and cheaper than most railed transit.  If you can afford one, they are much more convenient, but they generate lots of problems: congestion, pollution, paving of large areas for roads and parking, consumption of non-renewable resources, etc.

Big vehicle transit is only cost effective when something forces the price of small vehicle transit to be really high.   Most often this is congestion.  Our biggest cities are so dense that congestion causes travel by automobile to be nearly as slow as walking, and it's extremely difficult and expensive to find a place to park.  This forces people to use transit, and as a consequence, transit routes serve a lot of areas and schedules are such that most people can function well without a car.  Taxicabs and limousines serve the high end and can be time-savers for those that can afford them...someone else is paid to deal with the parking problem.

I'm only aware of one form of transit that has the unscheduled properties of cars and taxicabs, the short trip times of subways, does not pollute, does not require large parking areas, and is as cheap as buses running on roads.  It is called Personal Rapid Transit.  Small vehicles, grade separated, offline stations where the vehicle waits for passengers, computer controlled.  Because it's non-stop, it'll get you there faster than the subway or private car in the city.  It's electric powered, so it doesn't pollute.  The vehicles are small enough that moving them for a single passenger doesn't waste much energy, but special vehicles to move groups can be provided.