[adrian_b]

There are 2 kinds of sodium lamps, low-pressure and high-pressure.

The low-pressure lamps emit monochromatic light and they have not only the advantage of long life but they are also the only other source of light that matches the energy efficiency of converting electrical energy to light of the LED lamps.

So replacing low-pressure lamps with LED lamps does not produce any significant economic effects, it was justified only by the supposed advantage of enabling color vision.

However in many places high-pressure sodium lamps have been preferred, which have a wider spectrum, so they allow some very poor color discrimination. The high-pressure lamps have a lower efficiency than LED lamps, so replacing them was justified by energy savings.

Outdoors at night, I prefer the monochromatic low-pressure sodium lamps, but sadly LED lamps have replaced them in most places.

[rapnie]

In my area and esp. in the countryside they have green led lighting on various roads as an innovation, with the reasoning that is both least disturbing to wildlife, and best for human vision to see sharply. The light color takes some getting used to, but I am quite a fan of it. Esp. when cycling at home at night through the fields it makes things seem extra serene and peaceful.