Subway systems are underground or elevated train networks designed to transport passengers quickly and efficiently within urban areas. They consist of multiple lines that connect various neighborhoods, making it easier for people to commute to work, school, or other destinations. Subway trains run on fixed schedules and are often a preferred mode of transportation due to their speed and reliability. These systems typically feature stations where passengers can board and disembark. Many subway systems, like the New York City Subway or the London Underground, have extensive routes and serve millions of riders daily. They help reduce traffic congestion and promote environmentally friendly travel options.