Historic Signals Still Standing

Two features of modern life in the railroad world are change, and loss.  One of the more visible indications of this can be viewed publicly in the form of lineside signals.  Of course, it’s necessary to admit at the start that the advent of signals was itself a form of change, although since they had positive features, particularly with regard to safety, they generally were welcomed. 

Maybe somewhere a hundred-plus years ago somebody complained about how they were ruining the pristine rural view of the countryside, but I suspect that there weren’t many holding that opinion and/or expressing it, perhaps along the lines of “if timetable and train order was good enough for my dad and grandfather, it’s good enough for me”.

While current signals rely on electricity to display their instructions to operating crews, one of the more popular early forms of signals came to be known as semaphores.  These devices utilized a movable arm that rotated on a vertical pole to display different aspects that were useful in letting train crews know whether they should stop or proceed, and in the case of the latter condition, whether at full/track speed, or something less.

They came in two basic designs, known as “Upper Quadrant” and “Lower Quadrant”.  In both cases, if the semaphore’s arm was in the horizontal position, “stop” was indicated.  “Proceed” for the upper design caused the arm to be rotated counter-clockwise, so that the arm (or “blade”, as it was often referred to) was in a vertical position.  For lower quadrant models, the arm rotated clockwise to a position approaching vertical in the downward direction.

Initially, semaphores did not utilize lights, making them not terribly useful for night operations, unless illuminated by some external source.  This problem was overcome by adding lights to this, making them useful for 24-hour use, as well as during daytime periods of inclement weather.  This addition enabled crews to determine their indication either by looking at the arm’s position or the color of the light in the signal.

Eventually, it became more efficient to put up signals that only used lights, which avoided both the structure of the semaphore arm and, with an exception, the mechanism (and the associated maintenance) needed to move the arm.  One type of color light signal, referred to as the “Searchlight” type also required a mechanism, since it worked by placing a lens of the appropriate color (green, yellow, red) in front of the single bulb (hence the ‘searchlight’ name).

As light-only signals began to take over, the Pennsylvania Railroad adopted what was known as the “Position light” (PL) signal.  It displayed lights of a single color, generally described as amber, behind a round metal disk, with multiple lights arrayed in vertical, horizontal and diagonal clusters (including a common light in the center) that retained the advantage of the redundancy inherent in presenting both lights and their positions, thus mimicking upper quadrant semaphore positions, as well as the fact that the loss of a single bulb didn’t cause operations to grind to a halt, since each position indication would have at least two lights still visible.

A variant of this type of signal was adopted for use by the Baltimore & Ohio. It used the same layout as the position light version, but substituted color in the appropriate hues.  No center bulb was required, since a single lit bulb of each color could convey the signal’s aspect.  The N&W adopted the PRR’s position lights initially, and later converted to a color position light system similar to the B&O’s.

Fast-forwarding to the twenty-first century, new requirements such as positive train control have caused many of the older types of signals to disappear from the railroad rights of way.  Where there still are lineside signals (signals in the locomotive cab have caused the demise of the external kind in a number of locations), they have become homogeneous, three-light/individual color aspects that lack the variety and character of their predecessors; fans often refer to these as “Darth Vaders”, a reference to the villain of the Star Wars series of movies.

Will the old soldiers seen in the photo above actually “die” (be replaced by the contemporary design), as seen here June 6, 2023 at Exton, Pennsylvania on Amtrak’s “Keystone Service” line, also used by SEPTA commuter trains, or just continue to fade away?  Time will tell, although the elegance of the PL signal’s design is apparent by looking at the signal head on the right, where two bulbs continue to suffice for displaying a “clear” aspect, even though the bulb at the bottom of the vertical column is not lit.