subway

A subway is an urban public transportation system that moves large numbers of people quickly within metropolitan areas. It is typically electric-powered and uses trains that operate on dedicated right-of-way, often with extensive grade separation from other traffic. In central areas, routes are frequently routed underground in tunnels, while outskirts may use elevated tracks or at-grade alignments. The term subway is commonly used in North America; in many other countries the same system is known as a metro, underground, or rapid transit.

Operation and design aspects vary by city but share core features. Trains run on fixed schedules with high initial capacity and frequent service, especially during peak hours. Electrification is usually supplied by an third-rail or overhead line, and modern systems employ automated signaling, loading platforms designed for accessibility, and safety systems such as platform edge doors in some stations. Vehicles are typically railcars or multiple-unit trains designed for rapid acceleration and high turning radii.

History and development followed the need to alleviate surface congestion. The first subway opened in London in 1863 as a horse-drawn or steam-powered tunnel line, followed by electric operation in later years. The United States began with the Tremont Street Subway in Boston (1897) and the New York City Subway in 1904. Since then, major cities worldwide have built extensive networks, making subways a backbone of urban mass transit.

Impact and challenges include high capital costs, ongoing maintenance, safety and crowding management, and the need for upgrades to aging infrastructure. Benefits often include reduced road congestion, lower emissions, and faster travel across dense urban cores.

---