Personal Rapid Transit (PRT) - personal monorail
PRT is an elevated monorail system with many small, driverless, electric vehicles (three or four people). It is ideally suited short "feeder/distributor", shuttle, and "circulation" operations at train stations, airports, office parks, and shopping centers. PRT provides non-stop, no-wait, 30 mph service.
Vehicles travel on elevated "guideway" 16' above the ground. Stations are located near building entrances. Many stations are situated along the route to minimize walking once the trip ends. Station guideway is separated from the main guideway - vehicles turn off onto a siding to pick up and drop off passengers. Because of these turn-offs, vehicles travel non-stop to the destination at 30 mph, bypassing intermediate stops and speeding at twice the average speed of autos on congested city streets below. PRT is a combination of concepts from monorail (Disneyland), automated people movers (San Francisco Airport), roller coasters, and automated highway systems (Governor Schwarzenegger uses GM OnStar "auto-pilot" in the science fiction movie The Sixth Day).
Passengers travel alone or with people of their choosing. Vehicle weight minimization greatly reduces the size of the elevated guideway and supporting columns, dramatically reducing construction cost and right of way acquisition (a rule of thumb is that guideway cost is proportional to the square of vehicle weight). Vehicles flow through the rail almost like data packets on the Internet, anticipating demand so that wait time is eliminated. In addition to improving commute alternatives, the PRT system eliminates mid-day stranding caused by many commute alternatives, by providing efficient transit to adjoining shops and restaurants.
PRT is an emerging technology under development in Minnesota (SkyWeb Express), Texas (Microrail), the United Kingdom (ULTra - this firm also has a Berkeley office), and via two separate Korean efforts: Vectus and KRRI. These five designs are all different. Three efforts have one or more vehicles and a section of guideway completed. First commercial deployment will be in 2007, at the earliest.
Group Rapid Transit (GRT) - 8 to 25 people per vehicle