It varied by railroad. In my working experience, I never saw any regulations requiring lighted switch lamps. I started fulltime in the I.C. RR in 1964 and IC had already removed the switchlamps. N&W still had some in yards at ground-throws, but they were reflectorized and no longer burned oil. Some of the yards up in Chicago area still had lighted switch lamps in the 60's.
They seem to be a casualty of diesels and stronger headlights .... reflectorized targets would do the job without the maintenance required. Still, it was great to see them scattered around a yard or on the mainline at night.
As Cindy mentioned, I also used to bring my two switchlamps up to Sumpter Valley for night runs on occasion. It just looks right at night.
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