Joke Collection Website - Public benefit messages - Why are more and more small and medium-sized cities also building subways?

Why are more and more small and medium-sized cities also building subways?

Subway is the only way for a city to develop and optimize traffic in space, so more and more small and medium-sized cities also need subway. Small and medium-sized cities are also developing, urban agglomerations are also increasing, and the need for convenient transportation is more urgent, so developing the subway is the best choice.