Municipal lighting is a huge market for LEDs. At least some LED street lights have been installed in most cities in the United States, and a few cities have been completely replaced with LEDs. There are many reasons for choosing LEDs for street lighting, but in 2016, when the American Medical Association (AMA) warned that certain LED street lights would adversely affect night driving and human health, their attractiveness declined. Since then, lighting experts and cities with enthusiastic LED street lights have been arguing over this warning.
AMA warns that high-intensity LED lighting is not good for night driving because the blue portion of the LED white light spectrum is too strong. It produces glare that affects driving. In addition, AMA said that these frequencies of light can inhibit melatonin in the human body, causing problems such as insomnia, daytime productivity, and even obesity.
AMA recommends minimizing the output of the blue portion of the spectrum and increasing glare shielding. The quality factor of the source color appearance is the correlated color temperature (CCT), expressed in degrees Kelvin (K). Most installed LED street lights have a rated CCT between 3,000K and 4,000K. Due to the influence of blue light, AMA recommends that road-mounted luminaires should be no higher than 3,000K.
The Municipal Street Light Solid-State Lighting Alliance (MSSLC) within the US Department of Energy (DOE) has been an important source of response to AMA’s questions. MSSLC believes that CCT is not the only consideration when measuring the melatonin output of LED lighting.
When discussing LED street lights, we can often see the new word melatonin. Melanopsin is a luminescent pigment in the retina that is directly related to the circadian rhythm. Melatonin describes how certain types of light affect the human sleep cycle by activating black opsin. LED street lighting is exactly the same.
MSSLC said that the evaluation of the melatonin output of LED street lights requires consideration of many factors beyond CCT, including lighting output, luminaire type/distribution, and lighting design. Lighting engineers can balance these factors and design LEDs with higher CCT levels, but have to reduce melatonin output to the range recommended by AMA.
Portland, Oregon, USA, has begun to replace sodium lamps before the AMA issued a warning, and it continues. The city has about 45,000 street lights, and now all almost are LED lights, most of which are 4,000K lights. Decorative lights (such as in urban parks) are all 3,000K. On the Portland Municipal website, the Portland Department of Transportation (PBOT) has detailed AMA warnings on FAQs for new lighting, including a number of additional information links. Many Portlanders tend to be absolutely absolutistic about health warnings.
Other cities that have replaced most sodium lamps with LEDs include Boston, Los Angeles, and Seattle. However, in other US cities, the vast majority of street lights are still high pressure sodium lamps (HPS). The sodium lamp can be identified by its unique orange-yellow light. This type of lamp is popular in street lighting because it is more efficient than incandescent and fluorescent lamps.
The downside is that the City of Portland found that HSP streetlights have too much light concentrated in the bottom area of ??the pole, not enough to illuminate the space between the poles. The sodium lamp is also a single color, and it is said that color distortion can make it difficult for some people to cope. In addition, sodium lamps are difficult to handle due to their mercury content.
For municipal lighting, LEDs are expected to reduce maintenance and energy costs and are more durable than all other options. PBOT says they must replace the old sodium lamp every five years, and the new LED is expected to last for 24 years.
The price of LED lights has been steadily declining and is expected to decrease further. PBOT said that they installed a specific brand and model of LED lighting (Leotek ECobra), the cost of which was priced at $500 in 2000, but fell to $124 by 2018.
HPS lights are still cheaper at $110 each, so if a city wants to replace 50,000 street lights with LEDs, it will cost an additional $700,000. Therefore, the municipality has been fighting for funds, even for a large city, this is not a small amount.
Even if the cost of purchasing HPS is lower, in the long run, LEDs will last longer and will be much more economical. Before a city with LED street lights has to replace a street light, the city using HPS will spend two more rounds of replacement. In addition, as reported by PBOT, “As LEDs last longer and easier to repair, the city expects maintenance costs to be reduced by 75% over the life of the LEDs.”
The new street lamp consumes 29W per lamp, while the replaced sodium lamp is 118W. Supporters of LEDs also assert that LED street lights have less light reflections than sodium lamps and can reduce light pollution.
Assuming that the engineering proposal for LEDs is correct, even if the upfront costs are slightly higher, LEDs have become a better economic option for municipal road lighting. Even though AMA’s biggest concern about LED street lighting has been confirmed, the economics of LED street lights are also very attractive, and it is better than people’s concerns about health issues. It seems inevitable that the yellow-orange light accompanying urban life will eventually become a memory.
For municipal engineers who want more information, MSSLC is a major source, including engineering data for many lighting types. The US Department of Energy established MSSLC in 2014 to help cities consider the use of LED street lights. MSSLC operates within the US Department of Energy’s Office of Energy Efficiency and Renewable Energy and “represents coordination between interested cities, power suppliers, government agencies, and other organizations to minimize duplication of effort and associated risks. Expanded to multiple places.” It is essentially a user organization backed by the US Department of Energy resources.
These “resources” mainly refer to the knowledge base. According to federal standards, the budget for this alliance is only a few million dollars. That is to say, providing information about the available technologies and occasionally providing a modest grant is enough to get some cities to start. Cities that want to consider installing LED lighting do not have to start from scratch and can benefit from the experience of other cities that have already adopted the technology.