When traveling the rails you will occasionally see signal stanchions like this one, with lights arranged on a circular metal background. These railroad signals were developed by the Pennsylvania railroad in 1918, and with modifications, it’s still used by Amtrak, Long Island Rail Road and other lines (the LIRR was owned by the “Pennsy” for several decades).
The arrangement of the red, yellow, and green lights on the signal tells the train engineer whether (s)he should proceed full speed, proceed with caution, stop, or a variety of other options. This PDF outlines the full range.
You can tell this is an older signal since use of the center lamp was abolished in the 1980s.
The signal can be found on the railroad trestle on 84th Avenue between Babbage and Bessemer Streets in Richmond Hill. The tracks carry freights using the LIRR “Montauk” tracks from Long Island City to the junction at Jamaica. The tracks used to carry passenger service but only once per day since 1998, and even that was eliminated in the early 2010s.
The date 1923 is stamped in one of the concrete supports. This means the tracks ran at grade until that year, when they were elevated to avoid auto traffic problems.