Following the Poles Inc era, is the traffic signal dark age, where lower quality plastic signals started rolling in Pennsylvania. This era began sometime around the Late 1970s, and lasted up into shortly after the turn of the century, I would consider the end of this era when signals began switching over to LEDs. Pennsylvania finally stopped installing the flatback design of the Eagle in the Late 70’s, stopped using mast-arms made by Poles Inc, switched over to using Durasigs and began using normal mast-arms. Thus, the dark age of signals was born. No longer were signals made out of harsh aluminum that could withstand harsh weather, instead we had cheaply produced plastic crap. Especially Durasigs, the first and second gen ones were horrific and had visors as brittle as paper. Poly LFEs were being installed in Pennsylvania throughout the 80’s too, and they had paper thin visors. The aluminum signals weren’t any better too, due to the chemistry of the type of aluminum being used in this time period, the paint couldn’t stick for long, as the signals would begin to fade, even after just four or five years of service. The suburbs had mostly LFE, Safetran, Durasig at this time, while Philadelphia used mostly TCT and Eagle Mark IV.