Subway trains serve as a form of mass transit and provide an alternative to private and public above-ground street transportation. Riders pay a fee and enter and exit through strategically placed stations throughout the city. Subways are a convenient and affordable form of public transportation and help ease traffic congestion in city streets.
Locomotion and the Third Rail
Subways get their power through an exposed electrical line known as the third rail, which runs alongside the two rails the train cars ride on. Subways do not use gas-fueled combustion engines because the exhaust in the enclosed subway tunnels and stations would cause carbon monoxide poisoning to riders. Since the third rail is an exposed power source it is extremely dangerous. Touching a third rail results in electrocution.
Subways can also run above ground; many subway lines run on elevated tracks at some point on their routes. At this point they are commonly referred to as the El (for elevated) train. An example of this would be the number 6 subway line in New York City. In midtown Manhattan it is called the subway, but in Harlem and the Bronx it is the El, even though it is the same train in both places.
Subway trains are driven by operators, or conductors, who sit in a booth at the front of the train and use a handheld device similar to a video game joystick to operate the train. There are no foot pedals on most modern subway trains, though some older model systems do have them. The acceleration and braking are done with the joystick and buttons on a control panel. The conductor is also the one who makes announcements over the public address system in the train and opens and closes the doors of the cars at stations.