North American Rail Systems by Size
Thank Collier, a commenter on Rebuilding Place in the Urban Space, for this one.
The same as the link below, only this is for all of the subways/light rail/etc. for North America.
However, they're obviously not to scale to the size of North America (for some reason, it took me a little bit to realize that.) OTOH, it's in GLORIOUS TECHNICOLOR! :-)