I also assumed systems like BART were considered "light rail". Below is a definition for others who may also not know the difference. The American Public Tran

I also assumed systems like BART were considered "light rail". Below is a definition for others who may also not know the difference. The American Public Transit Association defines light rail and heavy rail respectively as follows: Light Rail is a mode of transit service (also called streetcar, tramway, or trolley) operating passenger rail cars singly (or in short, usually two-car or three-car, trains) on fixed rails in right-of-way that is often separated from other traffic for part or much of the way. Light rail vehicles are typically driven electrically with power being drawn from an overhead electric line via a trolley or a pantograph; driven by an operator on board the vehicle; and may have either high platform loading or low level boarding using steps. Heavy Rail is a mode of transit service (also called metro, subway, rapid transit, or rapid rail) operating on an electric railway with the capacity for a heavy volume of traffic. It is characterized by high speed and rapid acceleration passenger rail cars operating singly or in multi-car trains on fixed rails; separate rights-of-way from which all other vehicular and foot traffic are excluded; sophisticated signaling, and high platform loading. Reference: http://metro-cincinnati.org/?p=1566 http://metro-cincinnati.org/?p=1566