White squares seem to be a must. If you place signals on both sides but not on the white square you get a number of uni-directional segments that prevent trains going either way. At least that's what happened here.5thHorseman wrote:Signals on one side of a track make the track one directional. You can have a double headed train that goes back and forth if you put signals on both sides of the track.d3x0r wrote:OH ya I remember... signals make tracks one directional; so I can't have a double headed train that just goes back and forth, huh?
Specifically, place the signals on the white squares opposite the signals you already placed.