Street Cars and Historic Trolleys
Trolleys are systems that historically ran mainly or completely along streets but are capable of running on any railroad track. With low capacity and frequent stops, passengers usually board at street- or curb-level (but low-floor trams and level boarding platforms may be used). These can be called trams, streetcars, or trolleys.
San Fransisco streetcar (similar to New Orleans'/Memphis' streetcar systems)
Monorail is a transit system with a track consisting of a single rail (actually a beam), as opposed to the traditional track with two parallel rails. Monorail vehicles are wider than the beam they run on.
Open since Summer 2004, the Las Vegas Monorail attracts over 18,000 riders a day. Jacksonville's Skyway is a peoplemover that makes use of monorail technology.
Light rail is a relatively new term, as an outgrowth of trams/streetcars. Speeds are usually higher, and articulated vehicles may be used to increase capacity. These systems can run either within the street or on their own dedicated right of way, and can be either electric or diesel. Light Rail can not be operated in conjunction with freight trains, which can increase the implementation costs.
Minneapolis Hiawatha light rail line (a light rail system is currently under construction in Charlotte).
Heavy Rail/Rapid Transit
Rapid transit typically runs grade-separated from all intersecting roads, in tunnels or on elevated structures, or in rail cuts in outlying areas. Trains typically run faster than light railways, and stops are less frequent. Platforms are usually level with the typically high floors of the trains, and trains can reach ten or more cars in length (with multiple-unit operation), providing more capacity than light rail at higher headways. Electricity is usually provided by a third rail, though overhead wires are sometimes used, particularly by systems such as the Tyne and Wear Metro which run extensively above ground. Fares are collected before boarding, and usually proof of payment is required to even enter a station's platforms. Systems of this type can be called metros, subways, undergrounds, elevated railways, or sometimes heavy rail, though this term is more commonly used to refer to mainline and regional railways
Metrorail - Washington, DC (similar to Atlanta's MARTA & Miami's Metrorail)
Regional rail, or commuter rail, runs on trackage often shared with intercity rail and freight trains. They typically provide rail service between a central business district and suburbs or other locations that draw large numbers of people on a daily basis. Commuter rail trains are typically built to higher standards, as they run at higher speeds are at risk of more severe crashes. This distinguishes commuter rail from interurbans, which use light-rail vehicles on tracks through lower density areas. The development of commuter rail services has become popular today, with the increased public awareness of congestion, dependence on fossil fuels, and other environmental issues, as well as the rising costs of owning and operating automobiles.
Rail Runner - Albuquerque, NM
Commuter Rail is the rail transit system that Metro Jacksonville encourages JTA to investigate, as it tends to be cheaper than light and heavy rail systems.