In the day of Timetable and Train Order operations, trains signals were important, because they helped identify trains, and they let following and opposing movements know that everybody was in the clear when passing or meeting other trains. Train Signals include headlights, which marked the front of the train, classification signals, which indicated the type of train, and markers, which indicated the rear of the train. The 1946 Book of Rules is illustrated, so it helps us visualize the verbiage.