Anticipating change is key to documenting the railroad. In nearly three decades of photography along the former Pennsylvania Railroad Main Line, I’ve tuned my images to clues of this route’s past. While the PRR vanished into Penn Central in 1968, key PRR infrastructure has allowed necessary visual cues that retain elements of the old railroad. Among these are PRR’s iconic Position Light style signals that date to the steam era, and have survive the decades of change. However, a wise photographer will have noted that this style of signal hardware is out of favor. While Norfolk Southern has been gradually replacing its PRR era signals with color lights, I’ve learned that a recent NS application with the Federal Railroad Administration includes elimination of most remaining wayside signals from its former PRR Main Line between Harrisburg and Pittsburgh.

The writing is on the wall for these signals. Among those to go are favorites on the ‘west slope’ (between Gallitzin and Johnstown, Pennsylvania). I worked this area intensively in summer 2010, making an effort to capture trains passing former PRR Position Lights. Be forewarned: the signals that protected trains hauled by PRR’s magnificent K4s and M1b steam locomotives and have survived these long decades will soon pass from the scene.

I researched the development of PRR’s Position Light signals for my book Railroad Signaling. Here’s an excerpt:

PRR’s first position lights were installed in 1915 along the Main Line between Overbrook and Paoli, Pennsylvania, in conjunction with its new 11,000-olt AC overhead electrification. Early position light signals featured large background shields to protect the view from effects of harsh backlighting. Aspects mimicked those of upper quadrant semaphores by using rows of four lamps. After a few years of service these position lights were deemed successful. However, before PRR adopted the signal for widespread application, the form of the position light signal head was refined: Each head used rows of three lights oriented around a common center lamp with the outer lamps forming a circle. Lamps were mounted on bars with a circular background panel affixed over the lamps and shades to prevent backlighting. Traditionally this panel was made of Armco iron, measuring 4 feet 4 inches in diameter, with 7-3/4 inch holes punched in it for the lamps. Each single head can display several basic aspects: ‘clear’, represented by three vertical lights; ‘approach’ by diagonal lights at a 45 degree angle running from the 1:30 clock position to the 7:30 clock position; ‘restricting’ by diagonal lights at a 45 degree angle running from the 10:30 clock position to the 4:30 clock position; and ‘stop’ (or ‘stop’ and proceed) by three lights running horizontally. An individual signal head is only provided with lamps for the aspects it is expected to display and unnecessary holes are covered over. The lower of two heads, tended to use a slightly different shape for the shield panel. By using two heads, a great variety of speed signal aspects mimicking those of two and three head semaphores are possible. Slow speed aspects are provided by dwarf position signals that use a slightly different light pattern.