The term passenger railroad is defined to mean any conventional rail vehicle operating on track connected to the national railroad network. Passenger rail trains may be hauled by diesel locomotives or electric locomotives. Conventional railroad trains are limited to a maximum gradient of about 6 percent, although they usually are designed to operate with only a maximum of a 2 percent grade on most mainlines, with some exceptions. In addition, an older mode primarily used for transit applications, the monorail, has been proposed in various forms for higher-speed intercity service. The monorail concept used a single elevated beam.
Vehicle can ride above the beam, hang from the beam or run astride the beam.
The concept has been in operation since the1950s in amusement parks, downtown circulars and airport AGT systems. In Japan, some monorail systems are used between downtown areas and airports.