Since subways exist below ground level, passengers access the subway terminals through designated stairways or platforms that lead them beneath the streets. Passengers pay a toll to ride the subway. The fee is set by the city.
Subways operate similar to trains in that they stop at various terminals to pick up and drop off passengers. Many subway trains run simultaneously on various tracks and have their own routes. Passengers are required to pay attention to where they need to go so that they can ride the appropriate subway.
Subways run on an electrical line called a "third rail," rather than being fueled by gas. A third rail is an exposed electrical line that powers the subway train through the electrical current. Consequently, electrical outages in a city can cause the subway trains to stop running.
While subway trains stay primarily below ground, some subway trains have routes that lead them to above-ground stations or run on elevated tracks, such as the El in Chicago, Illinois.