Because newer light technology, like T8 and T5 fluorescents, provides much better color rendering than older technology like metal halide, it is possible to do an interior retrofit that dramatically reduces energy consumption without affecting the quality of light that people perceive. However, we have yet to accurately calculate the effect on pedestrians and drivers when the same approach is taken with street lights. There is a point where reducing wattage levels may put older drivers and pedestrians at risk.
That is the focus of research currently being conducted by the Illuminating Engineering Society (IES) Roadway Committee. Until that research provides conclusive results, highway lighting will continue to be based on the American National Standard Practice for Roadway Lighting (RP-8-00), published by the IES in 1999. The goal of these guidelines is less about reducing energy consumption than reducing nighttime accidents, aiding police, facilitating traffic flow, and promoting business during nighttime hours.
However, in addition to these standards, each city and town has its own set of rules concerning streetlights on roads other than major highways. And this is where they may find energy-savings opportunities. In general, there is more leeway to lower light levels in areas where speed limits are lower.
There is a variety of technology on the market that can achieve this goal. Induction lights, for example, consume a fraction of the energy of high pressure sodium, and throw a whiter, crisper light. They also have a longer life, which means lower maintenance costs. And they are less affected by temperature extremes and vibration than older exterior lights. LED street lights are another technologically sound option, although their high price tag translates to a much longer payback period. But whichever option is selected, the energy savings resulting from the replacement of old, outdated technology will eventually make the transition worthwhile.