The latest generation of LED (light emitting diode) exterior lighting is significantly more energy efficient than even high pressure sodium fixtures (the orange-tinted street lights that are commonly used). And what’s made the recent use of LED lights take off is the dramatic decline in prices for all types of LED fixtures. However, especially when considering exterior lighting like parking lot or roadway lights, careful consideration of the color hue of that lighting is important. The following is excerpted from the site of the non-profit International Dark-Sky Association (IDA), the recognized authority on light pollution.
…The price of commercial LED lighting products continues to drop, and capital cost recovery times for new LED street light installations, once 10 years or more, are now typically less than five years and continue to decline. As barriers to implementation fall, LEDs are gaining momentum as a lighting technology of choice in new outdoor installations.
Blue Light Is Bad
New technical capabilities often come with unanticipated challenges. White LED lighting often has significant levels of potentially hazardous blue light. IDA published a report in 2010 detailing the hazards of blue-rich white light sources. In the years since, scientific evidence has solidified around its conclusions.
Outdoor lighting with high blue light content is more likely to contribute to light pollution because it has a significantly larger geographic reach than lighting with less blue light. Blue-rich white light sources are also known to increase glare and compromise human vision, especially in the aging eye. These lights create potential road safety problems for motorists and pedestrians alike. In natural settings, blue light at night has been shown to adversely affect wildlife behavior and reproduction. This is true even in cities, which are often stopover points for migratory species.
The promise of cheaper outdoor lighting based on electricity and maintenance savings from LED conversion should be weighed against other factors, such as the blue light content of white LEDs. Blue-rich sources are the most efficient LEDs in terms of the conversion of electricity to light, and therefore have the lowest electricity cost to produce a given amount of light compared to “warmer,” less efficient white LED lamps. Every effort should be made to diminish or eliminate blue light exposure after dark.
There are already many white LED options now available on the outdoor lighting market and that number will only rise in the future. IDA has developed a set of recommendations for those choosing lighting systems. These suggestions will aid in selecting lighting that is energy and cost efficient, yet ensures safety and security, protects wildlife and promotes the goal of dark night skies. These include
- Always choose fully shielded fixtures that emit no light upward
- Use “warm-white” or filtered LEDs (CCT < 3,000 K; S/P ratio < 1.2) to minimize blue emission
- Look for products with adaptive controls like dimmers, timers, and motion sensors
- Consider dimming or turning off the lights during overnight hours
- Avoid the temptation to overlight because of the increased luminous efficiency of LEDs
- Only light the exact space and in the amount required for particular tasks