Microtrains are urban microtransport systems that are scaled down to faciltate design and construction by a village or neighborhood group. Rail networks are guaged and specified by users according cheifly to their collective economic character and the topography of their locale. Microtrains and the rail networks they travel along are generally built from readily-avaiable materials by independant engineers who are resourceful enough not to require large investment capital typical of standard rail systems.
Microrail guages are specified to accomodate standardized containers cheifly steel drums. In the USA, the 55-gallon steel drum is common and nearly ubiquitous. Many systems have been developed to handle these and their smaller counterpart, the 25-gallon drum. These can be excellent starting-points for guaging your microtransport causways. A common guage for US Cities is 18.5 inches – the wheel-base of a typical two-wheel hand truck.
Urban microtransport networks may or may not be "blessed" by the powers that be. For this reason, they often take on a sublime character as they wind through a neighborhood. Many times the "track" is simply a pair of earthen grooves and a steel cable.
Track segments can be built on the ground or suspended. Ground based networks often follow existing watercourses (known as "ditches" by some folks) conforming to a shallow groove shape with the cable lying in the point. Trains can be configured to pass through culverts crossing under roads and driveways. Trains can be suspended, but for obvious safety reasons, design is much more complex.
A microtrain tractor (traction component) can be mobile, stationary, intermodal, or a combination. They can be powered by electricity, biodiesle, humans, animals, wind. They can float down specially-designed channels passively powered only by gravity. Friction is nearly always dealt with using hydrology as long as watercourses and topography are at the center of the design process. (See w:Keyline Design|]].