@petergleick Passenger trains, one assumes. I imagine the freight network has a lot more in common with the red spiderweb in the first image.

As @pjohanneson guesses the overall network is denser but very little is used for passenger traffic. I also suspect that the “capillaries” of sidings and short lines weren’t visible in the older map and are largely gone today. Map from @openrailwaymap
@petergleick