Self-driving subways do exist in a number of cities. But generally, train operator aren't a huge cost. While taxi driver serves 1-2 customers at a time, a condu

Self-driving subways do exist in a number of cities. But generally, train operator aren't a huge cost. While taxi driver serves 1-2 customers at a time, a conductor can easily move around a thousand people in a train. Or compared with trucks, freight trains can be ridiculously long and so paying one guy is really nothing in comparison.