I never really thought much about street lights; they're so ubiquitous that it never occurred to me they require careful consideration and thought before placement. There are various advantages and disadvantages to be considered with any street light application.
An obvious advantage to street lights would be accident prevention, especially with pedestrians involved. There have been studies conducted that show crashes and fatalities occur far more often at night/in darkness, especially those involving pedestrians. Street lighting can reduce pedestrian crashes by around 50%. Supporting this fact is that lighted intersections and highway interchanges seem to cause fewer crashes than unlighted intersections.
The disadvantages could very well overpower the advantages, but so far they do not. There is a very real risk of being temporarily blinded by the brightness of high pressure sodium lamps after having become used to using your night vision. Also, because our eyes constrict and become adjusted to light much faster than they expand and become adjusted to darkness, there is danger in approaching an isolated field of light and then leaving it.
Different types of light bulbs are used in different settings with street lights. For large-scale industrial street lighting, HPS (high pressure sodium) lamps are desired for their intense brightness and relative low energy usage related to light output. HPS lamps are not the best for roads or public streets, however, because the yellow light makes it difficult to discern objects and people. Public locations are best lit by HID light bulbs
such as metal halide bulbs
, which provide a bright white light in which objects appear clearly and easily. Mercury vapor lamps
are much the same as metal halide in that their light output is white and clear.
I wonder if metal halide and mercury vapor technology has been considered for consumer light bulbs. I suppose it probably has, but I imagine the technology is best used in high-wattage large-scale applications.