The major lighting technologies used for street and home lighting are incandescent, mercury vapor, high pressure sodium (HPS) and low pressure sodium (LPS). In incandescent lights, a metal filament is heated to high temperatures which results in excess energy being wasted in the form of heat. Mercury Vapor, HPS, and LPS are gas discharge lights which pass an electric current through a container of gas, causing it to give off its characteristic bands of light. Incandescent lights emit an almost complete spectrum of light (that spreads from the infrared to the ultra violet). Mercury vapor emit a very bright bluish white light. HPS emit a pink light, while LPS emit a monochromatic yellow. Rhodes Astronomy and Ham Radio Society
The single wavelength emitted by LPS is best for turtles because it is minimally attractive to hatchlings; however, for humans it is inferior due to poor color rendering. On the other hand HPS is not as good as LPS for the turtles but is more favorable than LPS for human vision. Mercury and incandescent both offer exceptional color rendering but are very attractive to turtles. Kansas City Power and Light Company LPS is the most efficient although costly, generating 80 -180 Lumens per Watt (LPW is basically an expression of the efficiency of a light). HPS generates 45-110 LPW, Mercury vapor generates 13-48 LPW, and incandescent generates 6-25 LPW. HPS is not as efficient as LPS, but is less expensive. Mercury is less expensive than HPS, but incandescent lights are the cheapest of all. A 55 watt LPS light can produce the same amount of light, while outputting less energy, than the an 100 watt HPS, 175 watt mercury vapor and a 400 watt incandescent light. 400 watt LPS streetlights are implemented on A1A in Volusia County which were installed by Florida Power and Light. Some people argue that yellow light is less pleasing to the eye than white light, but surveys conducted in America indicate that public opinion is indifferent to the color of illumination. In addition, police studies have shown that the color of light sources does not affect the crime rate. Rhodes Astronomy and Ham Radio Society The type of light that is emitted is not the only concern; how the lights are mounted or positioned has a paramount effect on its "turtle friendliness." Globe style lighting is of a particular concern, due to its omnidirectional illumination. Illustrated in the picture below, globe lights produce a significant amount of ambient light, which unfortunately is immoderate. There are many types of lighting fixtures but the most appropriate ones are those that allow only illumination to reach the area needed. In addition the lower the lights are placed, the less likely they are to reach the beach. Instead of replacing old lighting fixtures, it is possible to shield lights with solid or tinted visors, and to add a lighting fixture to limit the direction of the light emitted. Generally this is a less expensive way to eliminate the light pollution. Tinted lights or shields that block out the short wavelengths of light and let the long wavelengths pass, are also available for most styles of lights. These should be used where lights can't be blocked with a solid visor. Lighting is necessary for safety, but if it is visible from the beach, they should emit a frequency that the turtles don't respond to.
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