Streetlights are needed by everyone. They illuminate our roads and pathways in order to make them safer for us to use, giving us a sense of security.
Street lighting shall be designed to provide the lighting necessary to assure adequate vision and comfort along public streets, to prohibit glare, and to minimise glare and adverse impacts on drivers, pedestrians and adjacent properties.
- All street lighting fixtures, especially in conservation areas, both Rural Conservation Areas (RCA) and Urban Conservation Areas (UCA)* should be full cut-off fixtures.
- The levels of illuminance should be appropriate for the area.
Light trespass is a major issue locally with streetlights. We often see home-made baffles of all sorts attached to streetlights near to bedroom windows and terraces. This problem is solved using full cut off light fixtures, as shown below.
The type of luminaire mostly favoured nowadays in order to reduce skyglow and light pollution is the flat glass full cut off (FCO) luminaire. This is defined as a luminaire “which, when installed at the specified design attitude gives zero intensity at and above the horizontal.” (BS 5489, Part 1, section 2.28), shown below.
There are professional standards by which road lighting has to be designed and installed. Both Europe and the US have their standards which are effective in reducing light pollution.
British Standard BS 5489 deals with aspects of road lighting, as does the US IESNA RP-8-2000 publication, issued in summer 2000.
The following are extracts from both publications:
“Lighting schemes in environmentally sensitive areas, seen from within these and adjacent areas, should be given particular attention. Such areas include green belts, national parks and areas of outstanding natural beauty. Similarly, schemes close to the edge of existing residential areas should also receive special attention. In these cases the light distribution should be controlled to minimise light spill on adjoining areas, by selection of an appropriate installed intensity class from Table A1 of prEN 13201-1.
FCO luminaires should be considered in the following situations :
- traffic routes in environmentally sensitive and open areas (BS 5489, Part 2, clause 4.3, and Part 8).
- roundabouts and mini roundabouts, particularly in environmentally sensitive areas and/or with unlit approach roads (Part 4, clause 8.6)- elevated roads and bridges (Part 6, clause 3.1)
- motorways in open areas (Part 10, clause 3.6)
In residential areas, preference should be given to the use of luminaires which are designed to reduce the upward light output ratio (UWLR) to a minimum. Precautions should be taken to avoid unnecessary light intrusion into adjacent properties, however, a limited level of illumination onto front gardens and the face of properties can be beneficial in enhancing the appearance of the area and protection of property. Intrusion levels should not exceed those specified in the ILE guide ‘Guidance notes for reduction in light pollution’.”
from BS 5489
Luminous flux above the horizontal does not benefit roadway lighting but can contribute to glare and may be considered visual clutter.
“Luminous flux above the horizontal also adds to skyglow. Many people consider sky glow undesirable and even offensive.”
Unless it is essential to have luminous flux aimed above the horizontal…non cutoff luminaires should not be used for new roadway lighting.
Non-cutoff luminaires inappropriately used may be considered a waste of energy.
Cutoff and full cutoff should be strongly considered.”
Existing road lighting varies widely in the amount of light spill produced and its angular distribution. Full Cut Off luminaires for road lighting have become very widely used overseas in recent years but are unfortunately very rare in Malta. In many of the light pollution ordinances in force in many parts of the world, none of the light emitting part of a road lighting luminaire is permitted to be lower than the horizontal edge of the cutoff shield. However, cutoff luminaire specifications often allow a small percentage of the light to be emitted above the horizontal, presumably to take account of luminaire orientation misalignment, diffraction, and manufacturing and measurement tolerances, as shown below.
Alternatives to road lighting
Especially in rural areas, preference should be given to passive means of warnings to drivers and pedestrians. These include installation of reflectorized roadway markers, lines, warnings or informational signs and reflectors attached to bollards at the sides of the road. These are used in many parts of the world, as in many cases these eliminate the need for the use of artificial lighting altogether and thus should be seriously considered.