A subway line is an underground or elevated train system that transports passengers within a city. It consists of multiple stations where people can board and disembark. Subway lines are designed to reduce traffic congestion and provide a fast, efficient means of public transportation. Typically, a subway line is part of a larger network that connects various neighborhoods and key locations, such as downtown areas, universities, and airports. Trains run on a fixed schedule, and riders can purchase tickets or use transit cards for access. Many cities around the world, including New York City and Tokyo, have extensive subway systems.