PATH runs on its own tracks, between the IND local tracks on 6th. The cross-harbor tunnels are cast iron, and are not straight. The PATH and NYCT systems are

PATH runs on its own tracks, between the IND local tracks on 6th. The cross-harbor tunnels are cast iron, and are not straight. The PATH and NYCT systems are incompatible. I think they use the same track gauges, but NYCT cars (either division) are too long to navigate some of the curves on PATH.