    automated guideway transit (agt) is a fully automated, driverless, grade-separated transit system in which vehicles are automatically guided along a "guideway". the vehicles are often rubber tired, but other systems including steel wheels, air cushion and maglev systems have also been used in experiments. the guideway normally provides both physical support, like a road, as well as the guidance. in the case of fixed-route systems, the two are often the same in the same way that a rail line provides both support and guidance for a train. for systems with multiple routes, most agt systems use smaller wheels riding on the guideway to steer the vehicle using conventional steering arrangements like those on a car. agt covers a wide variety of systems, from limited people mover systems, like those commonly found at airports, to more complex mass transit systems like the vancouver skytrain. in the people mover role the term "automated people mover" (apm) is sometimes used, although this distinction is relatively rare because most people movers are automated. larger systems span a variety of conceptual designs, from traditional subway-like systems to smaller car-like vehicles known as personal rapid transit (prt) which offer direct point-to-point travel along a switched network. between the two are larger vehicles sized for around 20 passengers, sometimes known as group rapid transit (grt), which blend features of the prts and larger systems. ==origins in mass transit== agt was originally developed as a means of providing mass transit services aimed at serving rider loads higher than those that could be served by buses or trams, but smaller than those served by conventional subways. subways were too expensive to install in areas of lower density - smaller cities or the suburbs of larger ones - which often suffer the same gridlock problems as larger cities. buses could be easily introduced in these areas, but did not offer the capacities or speeds that made them an attractive alternative to car ownership. cars drive directly from origin to destination, while buses generally work on a hub-and-spoke model that can up to double trip length. stops along the route increase this even more. agt offered a solution that fit between these extremes. much of the cost of a subway system is due to the large vehicle sizes, which demand large tunnels, large stations and considerable infrastructure throughout the system. the large vehicles are a side-effect of the need to h
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