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LED street lighting FAQ

LED street lighting and circadian rhythm


Do LED street lights (public lights) emit more blue lights than other sources, and does this lead to sleep disruptions?


There should be no worries regarding blue lights emitted from LED street lighting on sleep disruptions. There is nothing different about the blue light from LEDs vs. other light sources, as also discussed by the US Department of Energy. In fact, the current level of blue light is equal to or lower than moon light, which shines at 4000K. What’s more important is the intensity of light at night. Disruptive effect depends heavily on the amount of light, the timing, and duration of light exposure. Research shows that the light levels produced by LED street lighting are too low to affect the hormone levels governing our sleep behavior.
 
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Will applying LED street lights lead to circadian disturbances?


No. If properly designed and applied, LED lighting will provide its advantages and you can avoid potential unwanted side effects.
 

If you apply the right light, in the right place, at the right time, for the right situation, LED light can positively impact public safety and livability while also offering savings on energy and maintenance. Philips Lighting solutions are carefully designed for local applications taking into account the right optics and light intensity to benefit from the LED advantages and mitigate negative effects like circadian disturbances and glare.
 

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What’s the health impact of blue lights?


Blue light is important to our health and well-being, especially during day-time. Much of the research regarding potential negative health impacts of blue lights are based on intensity and duration of light exposure at night associated with shift work. These levels of exposure are significantly higher than common outdoor lighting applications and cannot be extrapolated to the reduced light level and shorter duration activities associated with street lights.
 
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Well-designed LED street lighting


What exactly does ‘well-designed’ lighting mean?



Properly designed lighting addresses considerations such as visibility, alertness, safety, security, optical glare control, color discrimination, lighting zones and impact on neighboring properties. In addition, it also takes into account special requirements such as “dark sky” preserves such as national parks, or concerns with protecting the local habitat.  By using the right spectrum, optics and light intensity it will help achieve the benefits of LED light and mitigate negative effects like glare and circadian disturbance.
 
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How can optics and controls help mitigate any negative impacts of public light?



Philips Lighting controls such as dusk-to-dawn sensors can automatically dim or turn off the luminaires according to the time of day, not only reducing energy consumption, but also reducing the potential negative environmental impacts. In addition, our solutions include shields to curtail uplight and sidelight and, most importantly, “optics” to minimize/reduce glare regardless of the amount of blue light or color temperature (e.g. 3,000K vs 4,000K) they deliver.
 
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Are we safe to move forward with (future) lighting renovation plans with LEDs?



Yes. Well-designed outdoor LED lighting will provide energy and maintenance savings and enhance your citizens’ well-being. Philips Lighting can aid you in tailoring the right light for the right situation and show how it can positively impact both public safety and livability while reducing energy and costs.
 
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Are there good examples of proper LED street lighting applications?



There are several good examples from the current Philips Lighting customers including:

  • Los Angeles, CA
  • San Jose, CA
  • Macon-Bibb county, GA
  • Jakarta, Indonesia
  • Grand-Prix, Singapore
  • Buenos Aires, Argentina

 

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Is there an industry standard for street lighting?



There are standards set by global and regional standarisation organisations such as CIE, IES, and CEN, which are widely recognized as industry best practice for design, production, and distribution of products. Philips Lighting complies with these standards.
 
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Preventing light pollution


Will LED street lighting lead to light pollution?



The use of LEDs does not lead to more light pollution, not if the lighting application is well-designed. On the contrary, when applying well-designed LED street lights you can be sure to effectively control scatter and glare while having far greater impact on reducing high angle brightness and light pollution.
 
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How can controls and optics help against the negative effects of public lighting?



Controls such as dusk-to-dawn sensors can automatically adjust the lighting according to the time of day, not only reducing energy, but also reducing the potential negative environmental impacts. Likewise, you can implement shields to curtail uplight and sidelight, and most importantly, “optics” to minimize/reduce glare regardless of the amount of blue light or color temperature they deliver.
 
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The impact of Color temperature


What is color temperature and why is it important?



Color temperature is measured in Kelvin, it’s a mathematical calculation derived from the Spectral Power Distribution (SPD) of a light sources. It allows for a wide variety of specific color combinations. LED lighting is available with various combinations of Correlated Color Temperature (CCT) and Color Rendering Indexes (CRI), which can result in various effects on vision. The color temperature is defined in degrees Kelvin, a warm light (yellowish) is around 2700K, moving to neutral white at around 4000k, and to cool white (bluish) around 5000K or more.
 

To demonstrate why it’s important, for example, in many outdoor applications, protecting the public with lighting that promotes alert drivers and a safe environment may be the highest priority. In those cases, the recommended color temperature is deployed with considerations for the space and those in it.
 

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Are there efficiency differences between different color temperatures?



The efficiency difference between cooler and warmer color temperatures are relatively negligible, especially as compared to the significant efficiency gained by transitioning from traditional incandescent to LED lights.
 
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What is the right lighting temperature for my city?



There is no one right lighting temperature for a city, as different situations require solutions tailored to that environment. As we design your implementation, we consider the right light, in the right place, at the right time, for the right situation.
 
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I heard that color temperature affects the efficiency of street lighting. What are the differences between CCTs?



Color temperature is an important aspect of color appearance related to how “cool” (bluish) or how “warm” (yellowish) nominally white light appears. Correlated Color Temperature or CCT is defined in degrees Kelvin; a warm light is around 2,700K, moving to neutral white at around 4,000K, and to cool white, at 5,000K or more. The energy efficiency differences between cooler and warmer color temperatures are relatively negligible, especially as compared to the significant efficiency gains by transitioning from traditional incandescent to LED lights.
 
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Putting kelvin and lux into perspective 



Recently there have been some articles discussing the desired colour temperature of LED street lighting. What is good, what is better? We also know that 15,000 lux is needed to suppress melatonin with your eyes closed. To shed more light on the discussions we put kelvin and lux in perspective. See some examples below:

 

  • The brightness of light fixtures in an office environment is usually approximately 500 lux.
  • The brightness of a computer screen (assume a computer screen  of 40x30cm and a viewing distance of 0.6m ) or TV is approximately 67-167 lux.
  • The brightness of a cloudy sky, a partly cloudy sky, a sunlit expanse of sand or snow, is approximately between 30.000 - 100.000 lux.
  • The brightness of a clear sky without cloud cover is approximately 5000 lux.  

 

Did you know that smart phone screens are in the 7000-8000k range?

 

 

 

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