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Denmark updates National Road Lighting regulations to include 'Good Light' and reduce light pollution

April. 2025; Jakob Zeihlund, The Danish Road Lighting Group &  Joachim Stormly Hansen, GLG Science Advisor and Ocutune.


Good light during the evening and night is very important. Aim to keep lighting below 10 lux three hours before bedtime by avoiding bright lights! See our 4 steps to good light.


In December 2024, the new and updated version of the Danish Road Lighting Handbook was published. This handbook is one of the most used Danish standards to meet the Danish Road Lighting Guidelines, and is heavily adopted within state roads, municipalities and road infrastructure.


In May 2024, the Danish Road Directorate published the report “The Impact of Lighting on Animals, Plants, and Humans.” This report, along with international publications, has since formed the basis for the measures the Danish Road Directorate has incorporated into the recently updated road lighting handbook (standard).

So what’s new? – the handbook, among others, introduces three new terms and concepts concerning light pollution, good light and biodiversity. These also aim to align with recommendations such as Good Light Recommendations for light, and Human responses to light on the circadian system, and other brain targets of ipRGCs, sometimes referred to as ipRGC-influenced responses to light (IIL responses) (CIE, 2018 and CIE TN 015:2023). These new terms are:  

  • Environmental Zones 

  • G-index 

  • mDER (Melanopic Daylight Efficacy Ratio)  


The environmental zones are adopted through the CIE 150:2003 Guide on ‘the Limitation of the Effects of Obtrusive Light from Outdoor Lighting Installations’. The purpose of this Guide is to help formulate guidelines for assessing the environmental impacts of outdoor lighting and is also adopted in the new CIE standard EN 12464-2 for outdoor workplaces.

  

It outlines five environmental zones to establish a basis for outdoor lighting regulations. The aim is to reduce the overall light pollution by helping to limit, or in some cases eliminate, light pollution and its consequences. These zones range from E0 (Darkness, Dark Sky and biodiversity rich areas) – E4 (e.g. A city centre). They describe the various lighting environments and the surrounding context to a given site. Defining the environmental zones helps guide the designer into defining the maximum and minimum permissible levels to avoid obtrusive light and mitigate light pollution.


For each environmental zone it is recommended to make use of mDER for used light sources, the abbreviation of Melanopic Daylight Efficacy Ratio, which is defined by the CIE and introduced in the CIE S 026/E:2018 document. mDER shows the ratio of the amount of light in the range of melanopsin sensitivity (mEDI, using a ref. D65 light source) to the amount of photopic lux, the range of visual sensitivity. The other recommendations are to make use of a lower mDER ratio at night from 0.30-0.35, using the estimations of CIE TN 015:2023.  

  

Further to this, the G-Index is also introduced. We know that short-wavelength light if emitted and/or reflected to the sky, can allow for more Rayleigh scattering, which can potentially lead to more skyglow and light pollution. The spectral G-Index is a variable that was developed to quantify the amount of short wavelength light below 500 nm in a visible light source relative to its visible emission. The smaller the G-index, the more blue light a lamp emits relative to its total output. It is used in order to select outdoor lamps that minimise skyglow and ecological light pollution. The Spectral G-index was developed to get insight into the amount of short-wavelength light compared to the rest of the visual spectrum, with a guideline of minimum 1.5 for areas with a focus on Biodiversity. As such in their "core criteria", to mitigate light pollution, it is recommended that "in parks and areas considered by the lighting designer to be ecologically sensitive, the G-index shall be ≥1.5". For regular light sources, as a ‘rule of thumb’, this corresponds to an LED with a colour temperature of around 3000K and lower, which is also recommended by the Dark-sky association.


The introduced efforts seek to provide sustainable outdoor and road lighting which ensures user safety, as well as mitigating skyglow, providing access to the night sky and protect biodiversity, and to open up the discussions on this important field within outdoor lighting.


The full text can be accessed through the Danish Road Lighting Authorities:  

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