Temporary Lighting for Landscaping & Construction Works
The following measures can be utilised when undertaking landscaping and construction works to reduce the extent of light pollution:
- Lighting should be positioned and directed away from sensitive wildlife areas where practically feasible
- Light fittings, i.e. shielded lighting or cut-off hoods should be utilised to reduce the amount of light emitted upwards, glare/overspill and to direct light downwards for works
- Only the necessary amount of lighting should be used and all unnecessary lighting should be switched off, particularly floodlighting
- Any floodlighting installed for plant and equipment should only be utilised during maintenance operations
- All other ancillary lighting necessary for safe access throughout a site should be low intensity lighting
- Low-pressure sodium lights which do not produce ultraviolet light or attract moths should be utilised where feasible.
The positioning of street lighting in relation to trees and other vegetation types should be considered carefully.
The installation of street lighting and associated services should take into account the Root Protection Area (RPA) and the Construction Exclusion Zone (CEZ) for existing and proposed trees within a landscape design layout. This should minimise the requirement for pruning or removing trees at a future date.
In addition consideration should also be given to other vegetation types, including sensitive areas which may provide habitat for wildlife within or adjacent to a proposed site.
Light and light overspill from permanent street lighting is one of the major sources of pollution which can negatively impact upon insects, bats and birds. The selection of permanent lighting as part of a landscape design layout for a site should consider the potential for lighting to deter or attract insects and bats. There are a number of lighting types available for use:
- Low pressure sodium lights are typically the yellow lamps seen along roadsides. Light is emitted at one wavelength, contains no ultraviolet (UV) light and has low attraction for insects. However, the lamps tend to be large which makes it more difficult to focus the light from these lamps.
- High pressure sodium lamps (brighter pinkish-yellow lamps) emit light over a moderate band of long wavelengths, including a small UV component, which attracts insects preyed on by some species of bat. The lamp is of medium size and the light can be more easily directed than low pressure sodium. This is the predominant lamp now in use.
- Mercury lamps (bluish-white lamps). These emit light over a very broad spectrum including UV light to which insects are particularly sensitive. Insects are attracted in large numbers along with high densities of bat species particularly of the genera Nyctalus and Pipistrellus (Rydell & Racey 1993). These lamps are not generally utilised in new developments.
- Light Emitting Diodes (LED). The light emitted is more directional and produced in a narrow beam.
- White SON. This is whiter than High Pressure Sodium and has a larger component of UV light leading to the attraction of larger numbers of insects and bats.
- Metal Halide. This is a small lamp and therefore more easy to focus direct It emits less UV light than mercury but more than high pressure sodium. It comes in three forms: a) Quartz arc tube (HQI); b) Ceramic arc tube (CDM-T) and c) Cosmo which is a new ceramic form.
- Tungsten Halogen. This is a more directional light and often used as for security lighting.
- Compact Fluorescent. This is generally used in street lighting. It produces a white light that includes UV light. It can be used at a low wattage and therefore on a low output to achieve low lux.
Permanent street lighting and home security lighting should also adhere to a number of simple design and positioning measures, where practically feasible. These include:
- Limiting the height of lighting columns and directing light at a low level
- Directing the light to where it is needed to avoid spillage
- Use of shielded lighting or cut-off hoods (completely shielded on their sides using cowlings) to reduce the amount of light emitted upwards and glare and to direct light downwards to avoid spillage
- The incorporation of a flat glass face in the light which will direct the beam downwards to selected areas, i.e. no bulge below the light housing and installed at zero degrees to horizontal to mitigate against upward light spillage
- Lighting should be appropriately positioned away from more sensitive areas
- Only the necessary amount of lighting should be used
- The times during which the lighting can be used should be limited to provide some dark periods (Jones 20002)
- Lights should be selected that do not produce ultraviolet light and will not attract moths and hence bats preying on them, e.g. the selection of low pressure sodium lamps or similar instead of high pressure sodium or mercury lamps
- Lamps used should be fitted with UV filters.
- The brightness should be as low as legally allowable.
- Consideration should be given to using computer-controlled lighting such as that installed on the recently developed cycle/footpath along the Grand Canal between Inchicore and Ashtown, which automatically reduces lighting intensity to 1 Lux at ground level during the seasons when bats are most active.
1 Bat Conservation Trust (2008) Bats and Lighting in the UK. Bats and the Built Environment Series
2 Jones (2000) Impact of lighting on bats.