In the United States, probably the best comparison would be BART in San Francisco Bay Area and WMATA in Washingon, D.C. area. They act like a subway in city ce

In the United States, probably the best comparison would be BART in San Francisco Bay Area and WMATA in Washingon, D.C. area. They act like a subway in city center, and like a (commuter) railway outside. As a stretch, also look at SF Muni Metro which acts like a tramway/streetcar outside the dense areas, else like a "light subway" in the dense areas.