Compatibility of road lighting with star visibility

Abstract

The influence of city lighting on astronomical observations is analysed by using a single parameter for a whole town based on the upward light from the luminaires. This parameter separates the influence of the upward light on the maximum visible stellar magnitude and on energy saving from the unavoidable reflections from the illuminated surfaces, independently of the way light is scattered in the atmosphere. It is shown that extreme reduction of spill light leads to no appreciable benefit for astronomy and increases installation and energy costs.

Review of road surface photometry methods and devices – Proposal for new measurement geometries

“…A town can be treated as a single uniformly diffusing source; 56 most luminaires are hidden in cavities between buildings and few luminaires are not screened by buildings (typically on the boundary of the town or in large open areas). The road surface behaviour for light pollution is similar: light reflected by road at angles between 08 and 208 over the horizontal road plane have higher impact on astronomical observations too.…”

Spectral considerations for outdoor lighting: Designing for perceived scene brightness

“…In an analysis of more than 100 outdoor lighting site plans for various types of applications, Brons et al 14 found that the amount of light leaving an outdoor space was largely correlated with the average photopic horizontal illuminance specified for the application. In the outdoor site lighting performance (OSP) framework developed by Brons et al, 14 glow is defined as the average illuminance on the side and top surfaces of a virtual box enclosing an outdoor lighting installation (Figure 1); lower designed photopic illuminances for the outdoor lighting application results in less reflected light from pavement surfaces 15,16 and thus, lower OSP glow. Light source optics have some, but not a major impact on OSP glow.…”

Road Lighting

“…Such a zero-ULR installation will nevertheless result in some degree of sky glow because of light reflected upwards from the horizontal and other surfaces. Soardo et al (2008) in fact showed that an installation carefully designed to have strictly-limited direct upward light, may nevertheless result in a higher degree of sky glow than an installation with some less restricted direct upward light. This is because the luminaires of such an installation may be less efficient as far as the lighting of the road surface is concerned.…”