A monorail replaces the more usual two-rail transport system with a single track, and its vehicles either straddle the rail or hang from it. In the first type, the pillars supporting the rail can be of different heights, and so rough terrain can be crossed cheaply. In the second type the rail can be suspended above canals and rivers, taking up little valuable land.
In June 1825 Henry Robinson Palmer (1795-1844) opened a suspended monorail in Cheshunt, near London. Although designed to carry bricks, it could also carry passengers. For the United States Centennial Exposition of 1876, General Le-Roy Stone built a demonstration pillar monorail in Philadelphia. Other pillar monorail systems were built to carry agricultural products and mineral ores.
The most famous passenger-carrying pillar monorail was the Irish 9-mile (14.5 km) Listowel and Ballybunion railway that ran from 1888 to 1924. A German suspended monorail in Wuppertal started service in 1901 and is still in regular passenger-carrying use. In 1903 Louis Brenan patented a ground-level monorail with vehicles that were maintained upright by two large spinning gyroscopes. Fear of gyroscopic failure made this system short-lived.
One problem with a conventional two-rail system is that at high speed the train tends to oscillate from side to side, a phenomenon known as hunting. This does not happen on a monorail, allowing faster train speeds. A modern version of the pillar monorail was designed by the Swedish industrialist Dr. Alex Lennart Wenner-Gren (ALWEG). ALWEG monorails have been constructed in Florida, Japan, and Australia.
