Where light from an outdoor lighting installation shines into nearby properties and disturbs residents, it becomes a light immission problem. In Germany, protection against such "light pollution" is afforded by the Federal Ambient Pollution Control Act (BImSchG). The possibility of light immissions should be ruled out at the design stage.

LiTG publishes maximum admissible immission levels

Although no concrete ceilings are defined in statutes or administrative implementing regulations, help is provided by the Deutsche Lichttechnische Gesellschaft (LiTG) publication "Messung und Beurteilung von Lichtimmissionen" (Measurement and assessment of light immissions). In it, the LiTG publishes maximum admissible levels and details of the measurement and assessment methods used.

The Immission Control Committee of Germany's federal states (Länderausschuss für Immissionsschutz – LAI) has adopted these methods and ceilings in its guideline "Hinweise zur Messung und Beurteilung von Lichtimmissionen" (Measurement and assessment of light immissions) and recommends that they should be applied by environmental protection agencies. A number of federal states have issued "lighting guidelines" on the subject.

Protection of the starry sky

Light emissions which radiate upwards from densely populated areas and brighten the night time sky are known as "light smog".

Some European countries have already passed laws to protect the starry sky, others plan to do so in the future. The first to introduce legislation was the Czech Republic; Italy and Spain have followed suit.

The best way to minimise "light smog" to ensure that the light emitted by road lighting and exterior luminaires is directed entirely to where it is needed: on roads, paths and steps.