Subways are underground or elevated train systems that provide rapid transit in urban areas. They are designed to alleviate traffic congestion and offer a fast, efficient means of transportation for commuters. Major cities like New York, London, and Tokyo have extensive subway networks that connect various neighborhoods and key locations. These systems typically feature multiple lines, each identified by a unique color or number, and operate on a fixed schedule. Subways are not only crucial for daily commuters but also play a significant role in reducing pollution and promoting sustainable urban development.