The Addition of Color to PL Signals

NW Mailing List nw-mailing-list at
Mon Oct 29 15:42:14 EDT 2012

Perhaps you will enjoy the thoughts of Dr. Jim Calvert, Emeritus Professor of Engineering at the University of Denver, on the notion of adding color to PL signals. Dr. Calvert has written numerous articles on the history of railroad operating practices, and this clip is from his monograph "Notes on Pennsylvania Railroad Operations and Signaling."

"Curiously, some position-light home interlocking signals were equipped after 1955 with two red lenses to show the Stop aspect, the pivot light being extinguished. The first trial was at Overbrook on 25 September 1954. If this was done merely by installing red lenses, as it seems to have been, the result is a dimmer, less-distinct signal than the original row of three lights. Under bad conditions, it must become downright hard to see. I have been unable to find the reasoning behind this modification, but Waytel reports that it was ordered by a high official. I thought first that it was some ignorant regulatory influence, but it seems to be a result of the ignorant management by lawyers and accountants who took over about this time. At any rate, it is totally unnecessary and can offer no benefit whatsover."

-- abram burnett
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