"Metal Halide lamps emit a cool white light which makes for more accurate object identification and adds to our sense of security. This white light creates a skyglow similar to moonlight rather than the orange glow of HPS, and are only slightly less efficient at commonly used wattages. Metal halide is the preferred lamp for lighting applications in Burlington for both it's color rendering and energy efficiency."
It sounds like they just quoted the lighting manufacturers sales brochure.
They were almost right when they said that Metal Halide creates a skyglow similar to moonlight -- about three to four times as much skyglow as regular Sodium streetlight, due to the Rayleigh Effect of water vapor scattering blue light. But do you really want skyglow of
any color when skyglow is an indicator of wasted light?
Bringing us back to the types of vision
Scotopic Vision (moonlight) 10-
2 to 10-
6 cd/m² (or 'nits' for billboard people).
Mesopic Vision (porch light, residential streetlight) 10-
2 to 1 cd/m²
Photopic Vision (brightly-lit city centers, gas stations, billboards, and daylight) >1 cd/m²
(To give some idea as to scale of 'nits' or Candellas per Square Meter (cd/m²), Tulsa's LED billboards are 6,500 nits in daylight, 500 nits at night, for example.)
Where light of a color temperature of 2700 degrees Kelvin falls with respect to these types of vision depends upon the intensity of the 2700K light source.
At very low light levels (Scotopic) the eye is more sensitive to shorter-wavelength, bluer light (starlight, twilight, moonlight)
but some lighting manufacturers have assumed this would also be beneficial at much higher levels when in fact at higher levels different components of the eye are at work.
Here's another explaination of Color Temperature:
http://www.sizes.com/units/color_temperature.htmSo if I were to over-simplify a presentation for the mayor or council, It would be something to the effect:
The ideal outdoor lighting color temperature is 3000 degrees Kelvin, which is the color of incandescent light.