Subway

A subway is an urban railway system designed to transport large numbers of passengers efficiently, usually through tunnels or on dedicated tracks separated from ordinary road traffic. A subway train consists of several cars connected together and runs on rails. Most systems use electric power, supplied through a third rail or overhead equipment, to operate traction motors that turn the wheels.

Stations allow passengers to board and leave the trains, while signals and control systems regulate their movement and help maintain safe distances between trains. Some subway networks are mostly underground, whereas others include elevated or surface sections. The exact design varies from one city to another according to local geography, population and transport needs.

Subways can move many passengers without requiring each person to use a separate road vehicle. Their high capacity makes them particularly useful in densely populated cities, where road traffic can be heavy. Trains usually stop at regular intervals, and some networks use automatic systems to control speed, braking or even the entire train. Ventilation systems are important in underground sections because they help renew the air and manage heat.

Escalators, elevators and accessible platforms can make stations easier to use for people with reduced mobility. Subway networks are an important part of public transport in many cities and are often connected with buses, trams and other railway services. By concentrating many journeys on electric trains, they can help reduce road congestion and, depending on how the electricity is produced, transport-related emissions.