In practice, throughput is not the same. There are fewer cars underground that just park on the tracks, fewer traffic accidents, demos etc. Subways make you independent of almost everything that happens above ground. When Beijing introduced the subway system, that first allowed people to estimate quite precisely when they would arrive at their destination.
Also, fewer people plan to build a park underground or use that real estate otherwise. So the above-ground use of space is restricted to the station entrances. The calculation would even be different in places like Seoul, where the subway system doubles as a public bunker system.
In practice, throughput is not the same. There are fewer cars underground that just park on the tracks, fewer traffic accidents, demos etc. Subways make you independent of almost everything that happens above ground. When Beijing introduced the subway system, that first allowed people to estimate quite precisely when they would arrive at their destination.
Also, fewer people plan to build a park underground or use that real estate otherwise. So the above-ground use of space is restricted to the station entrances. The calculation would even be different in places like Seoul, where the subway system doubles as a public bunker system.
You seem to think of a tram. A metro is grade separated. So nothing, but the trains should be on the tracks at all times.
So this for example is a metro, but not a subway: