Sodium lights are trivial to block using optical filters. This is very common in astronomy. LEDs + phosphor, not so much, due to their wider spectrum. That l

Sodium lights are trivial to block using optical filters. This is very common in astronomy. LEDs + phosphor, not so much, due to their wider spectrum. That less is emitted directly skyward doesn't help if what's reflected off pavement can't be filtered out. (Pavement is surprisingly reflective even though it's "black".)