Letters
Sky glow and the color of road surfaces
Following the UK lighting designer Nigel Pollard's guest article on sky glow in IAEEL Newsletter 1/96 we have received some questions regarding light road surfaces and sky glow. One of the most often asked questions was whether lighter roads and surfaces, which reflect more light, should be preferred over darker surfaces, which reflect less light into the sky, or vice versa .Reply: The brighter the road surface material, the less light - and thus the less energy - is needed to illuminate it.
The brighter road surface materials also have positive implications for minimizing sky glow. Since less light is required to illuminate a lighter surface, we can use a smaller lamp which will radiate less light in all directions, including light radiated above the horizon. (Light emitted directly from a light source generally creates worse sky glow problems than reflected light.)
Ideally, if sky glow is to be kept as low as possible, then the reflectivity of the road surface directly upwards needs to be as low as possible, so what we really need are road surfaces that reflect the light at low angles (towards the driver) but not at high angles!
Nigel Pollard