One of the advantages of low-pressure sodium lamps is that they emit nearly all their light in a narrow spectrum which is easily filtered out. This leads to non

One of the advantages of low-pressure sodium lamps is that they emit nearly all their light in a narrow spectrum which is easily filtered out. This leads to non-existent colour rendition - everything is seen in shades of warm orange - but given that these lamps have been used for decades without too many problems this seems to be a surmountable problem, at least on motorways which are a major source of light pollution. If monochromatic orange light is deemed undesirable it might be worth experimenting with mixing three monochromatic red, green and blue sources which also can be filtered out. The combination of the three produces something close to (but not identical to) white light which provides better colour rendition.