The problem with having only car lanes is that they’ll always be congested, no matter how many lanes you add (look up induced demand). Trains have so much more capacity that we don’t run into this issue.
Basically, 4 car lanes=traffic jams twice a day vs. 2 car lanes + 2 train tracks= traffic flowing freely.
Of course a subway would be even nicer but those aren’t always an option because tunneling is expensive
So then are we really saving space if we keep it there or are we just using more to make train tracks?
The problem with having only car lanes is that they’ll always be congested, no matter how many lanes you add (look up induced demand). Trains have so much more capacity that we don’t run into this issue.
Basically, 4 car lanes=traffic jams twice a day vs. 2 car lanes + 2 train tracks= traffic flowing freely.
Of course a subway would be even nicer but those aren’t always an option because tunneling is expensive