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In this work, we propose an approach to estimating the amount of light wasted by being sent towards the upper hemisphere from urban areas. This is a source of light pollution. The approach is based on a predictive model that provides the fraction of light directed skywards in terms of a small set of identified explanatory variables that characterise the urban landscape and its light sources. The model, built via the statistical analysis of a wide sample of basic urban scenarios to compute accurately the amount of light wasted at each of them, establishes an optimal linear regression function that relates the fraction of wasted flux to relevant variables like the kind of luminaires, the street fill factor, the street width, the building and luminaire heights and the walls and pavement reflectances. We applied this model to evaluate the changes in emissions produced at two urban nuclei in the Deltebre municipality of Catalonia. The results agree reasonably well with those deduced from the radiance measurements made with the VIIRS instrument onboard the Suomi-NPP Earth orbiting satellite. [ABSTRACT FROM AUTHOR]

The paper considers the justification for the application of light-emitting diode (LED) technology to urban lighting. The results suggest that LEDs are convenient for architectural lighting and deserve to be considered for use in ambient lighting. The recently developed Commission Internationale de l’Eclairage (CIE) mesopic system enabled the inclusion of mesopic effects into a comprehensive techno-economic analysis, which dealt with efficiency, maintenance and financial aspects of the use of LEDs in street and roadway lighting. It is concluded that the average energy savings when using LED instead of high-pressure sodium (HPS) luminaires amount to 19–26% for single-sided, staggered and opposite layouts, although they are frequently negligible if mesopic effects are not included. The total costs of the LED lighting solutions, even including mesopic effects, are 1.36 to 6.44 times higher than those of the comparable HPS lighting solutions. Therefore, LEDs are questionable for street and roadway lighting. [ABSTRACT FROM AUTHOR]

Therefore, to take the human-centred integrative lighting approach one step further and account for architectural environment spill-over effects, there should be a realisation that lighting designers and architects I can i influence light exposure wherever humans are. Some state that lighting designers should provide the proper light at the appropriate time for their design projects, but they cannot influence a person's exposure to light when that person is somewhere other than the design location (e.g., in transit or at home). The realisation that the effects of light on humans are a complex interaction between multiple types of photoreceptors in the human retina fed the scientific discussion about "proper lighting design". [Extracted from the article]

The author reflects on the concept of lighting, outlined in several papers of the issue. An overview of the survey on the luminous environment at night in urban areas of Shanghai in China, the impact of different lighting quality installations on office workers, and the extensive experimentation on color rendering, discussed in the papers is offered. The editor highlights discussions on the calculation of daylight coefficients and the status of current photometry in the mesopic region.