Not sure to post here or on scenery or real trains forum. Want to install the MTH traffic lights, but can't recall if single or double heads were common for single traffic lanes in small town USA in 1950-early 60 (era I am modeling.) Googled but can't find any really old MUTCD literature that shows when double redundancy heads came into requirement. Do know the two or three second delay between all lights red then one set going green (intersection clearing) was fairly recent, so that is not a concern in 1950s.
As a kid didn't pay attention to lights in Pittsburgh area, let alone small outlying boroughs.