Traditionally, stationmasters and train engineers communicated by word of mouth or written notes. Any further communication depended on signalmen who walked along the track carrying colored flags. Better signaling became essential at the turn of the 20th century as the numbers of lines and trains traveling those lines increased. The signal rising above this South Deerfield, Massachusetts, station roof offered improved and safer communication that prevented collisions and saved lives. The position of the signal arms in this postcard view indicates that the track is clear. Arms raised horizontally indicate “danger” while arms raised in the intermediate position signal “caution.” White, red, and green lights on the pole communicated the same messages at night.