Monorail

A monorail was a type of train, a vehicle used for ground transportation on Earth and other planets. Per its name, the vehicle traveled along one track. Some monorails used electric or biofuel propulsion and wheels, while others floated above the rail with maglev technology.

Monorail tracks were usually elevated above the ground. An underground monorail was a type of subway.

Specifics
San Francisco's monorails were built 12 meters above the ground. The track was one meter wide and contained a highly charged conduit. 

A forcefield protected the Lily Sloane Complex in San Francisco Bay from warp core breaches. During the four-minute ride on the monorail from Starfleet Academy to the complex, vehicle cars would penetrate this forcefield, producing a momentary sensation of falling before the car's gravitational field compensated. 

Old monorail systems across the surface of moved cargo within automated tram cars. Manned stations provided manifests for its users, though many were unmanned. Newer systems used underground pneumatic tubes instead, which shunted cargo at high speeds without first having to load individual cars. 

History
By the late 21st century, New York City had a monorail network and elevated highways. 

In 2228 in Elysium City, bureaucrats discussed whether pylons on the monorail support system were stable enough, but Heston Prescott solved the problem. 

In 2273, Admiral Heihachiro Nogura rode a maglev monorail from San Francisco to Atlanta, then to Druid Hills and finally to Emory University, at the request of James T. Kirk. 

In 2284, after dating for two years, Tonia Barrows proposed to Leonard McCoy at a monorail station in San Francisco. He turned her down, though they eventually married in 2299. During a mind meld in 2312, Spock and McCoy relived the moment. 

Saavik once visited an automated monorail station on the outskirts of ShiKahr on. 

In 2368, cadet Jayme Miranda hitched a ride on the back of a monorail car as it left the Starfleet Academy station for San Francisco. She lost her footing and fell, but was caught by a protective forcefield before crashing to the ground. The fall was witnessed by Guinan. 

Earth monorail station locations

 * Atlanta
 * Bruggeman-Johnson Medical Research Center
 * Brooklyn
 * Centers for Disease Control and Prevention
 * Druid Hills
 * Emory University
 * Golden Gate Bridge
 * Lily Sloane Complex
 * Mojave
 * San Francisco
 * Sausalito
 * Starfleet Academy
 * Starfleet Command, plaza station
 * Starfleet Military Operations

Other monorail locations

 * Donico II, near the Donico Decorum and Diplomacy Corps building
 * Dyson Sphere
 * Elysium, in Elysium City
 * Denari, in the capital city of New Irla
 * Starbase Yorktown (Kelvin timeline)
 * , on the outskirts of ShiKahr