"간선" refers to a main route or line in transportation systems, such as buses or trains, that connects major areas or hubs. It serves as a backbone for public transit, allowing for efficient movement of passengers between key locations. In the context of urban planning, 간선 is crucial for reducing traffic congestion and improving accessibility. By focusing on these main routes, cities can enhance their public transportation networks, making it easier for residents to travel to work, school, or other important destinations.