Back when In was younger I remember ALL the city streetlights were mercury vapour, but the lamps I am pretty sure were
"clear", and gave off that harsh blue light as opposed to the whiter light I have seen from a " Coated" mercury lamp..
Most of the older sections of the city that were supplied from the older 4KV system also had a 4KV circuit that originated from the substation and fed pole top transformers that in turn fed the streetlighting. All of these circuits were in turn controlled from the head office downtown. Also was not uncommon if you had a good eye to see the lights of your house flicker when large sections of streetlighting were switched on..
About 14 years ago the city made the conversion to high pressure sodium, gone were all the mercs as well as the central switching system. All new " cobra head" fixtures had a photoswitch in the top and were tied into the mains supplying power to residental and commercial customers, although there are small sections downtown where decorative poles and streetlighting are supplied by a contactor and photoswitch arrangement located in a vault somewhere.
Recently though the decorative streetlighting as well as a few re-located poles outside of the University have been switched to Metal halide..
I find it makes the downtown look
"cleaner" and more attractive which is what this city needs, but for the suburbs, the HPS is here to stay.
A.D
