A subway system is an underground or elevated train network designed to transport passengers within urban areas. It typically consists of multiple lines that connect various neighborhoods, making it a convenient and efficient mode of public transportation. Subways are known for their speed and frequency, helping to reduce traffic congestion in cities. Subway systems often feature stations where passengers can board and disembark trains. Many major cities, such as New York City, London, and Tokyo, have extensive subway networks that serve millions of riders daily. These systems are usually operated by public transit authorities and are an essential part of urban infrastructure.