I live in a reasonably dark rural village but have half a dozen street lamps (a mix of LP sodium, metal halide and now LED), none of them are well designed, with very poor cutoff, even the LED (I suspect they went with the cheapest. The LED lamps probably do not even cut off the blue/UV spike that I believe decent models have these days. ) The pollution is significantly worse than when they were all LP sodium but sky background subtraction still deals with this very well, removing man made pollution and natural airglow/moonlight even when the sky is many times brighter than the spectrum eg
http://www.threehillsobservatory.co.uk/astro/spectra_46.htm
Robin