This used to be an aesthetic question, and therefore dismissed by many, particularly public works officials and highway engineers who came to believe -- or who we the taxpayers instructed to believe -- that getting the maximum light for the minimum cost was the primary mission.
But increasingly -- though to some of us not surprisingly -- studies are showing that we see significantly better under clear, white light as opposed to harshly tinted light, particularly outdoors at night where the ability to discern detail and motion, particularly in the peripheral vision, is put to the test.
There are now findings, too, that suggest that physically and psychologically we don't thrive under the most common type of lamp used in street lighting, high-pressure sodium. These studies are pioneering efforts, and I am not the best one to judge their methods and merit. But I find it significant that for the most part they confirm what ordinary people -- including a significant body of the general public -- have been saying, or perhaps just feeling, for years: that most cities at night are, today, awful. Distilled to its simplest, the argument where light is concerned is that people work, play, and feel better under illumination that more closely resembles the full-spectrum light of sun and fire which humans evolved with.