Wasted Light - Wasted Energy - Wasted Money - Environmental Degradation
...and the solution
Update March 2010
Adelaide's light pollution is typical of urban environments everywhere. The following most likely applies to your town and city too.
While many town planners are beginning to take notice there is still a long way to go. Far too many outdoor light fixtures used for business, advertising and security are still being installed without due consideration to the choice of the correct fixture for the task. The result is unnecessary skyglow, glare and light trespass. Mostly it is due to a choice of cheap, inefficient light fixtures, bad aiming, over-lighting and a lack of awareness of better lighting options.
Star-trail image courtesy Justin Tillbrook
Within the city up-light from thousands of unshielded light fixtures scatter upwards creating a pervasive sky glow obliterating all but the brightest stars. If all this wasted up-light were directed downward - where it is useful - only 6% of it would return upward due to reflections from road and other surfaces. Not only would this bring back many of the stars but improve lighting quality on the ground by reducing glare and even save on energy and money. The lone object in the washed out sky in this image is Mars. Taken from the coast at Semaphore South looking east toward the greater metropolitan area.
A typical view from an Adelaide backyard on an overcast night. Vast quantities of wasted uplight illuminates the cloud base creating a gloomy pall over he city. Residents pay for this wasted light through council and electricity rates.
Which kind of lights are good and which are bad?
THE GOOD, THE BAD, THE UGLY
THE GOODFully shielded fixtures direct light below the horizontal toward the ground. Top image: is one of the standard aero-luminaires fitted with a flat protector that prevents light from scattering sideways and upward. This avoids glare and improves the quality of lighting. These fixtures are known as full-cutoff in that they cut off light from escaping sideways and upward. Fitted with a LPS or HPS (low-pressure or high pressure sodium) lamp they are efficient and make a good choice for many kinds of outdoor lighting especially roadways. Examples can be seen in some metropolitan council areas especially in parts of Adelaide CBD where they are replacing older glarey fixtures. Lower image shows the preferred flood-light fixture for areas such as car yards and parking lots. Often fitted with a less efficient mercury or metal-halide (white) lamp, the design however avoids glare and light trespass without compromising security.
THE BADTop image: These "cobra-head" fixtures are fitted with a dome or cylindrical shaped lens that emit a substantial portion of their light uselessly sideways and upward creating glare, light trespass and sky glow. These fixture are known as semi-cutoff. They are currently the standard on the state's arterial roads and many residential roads. They can easily be refitted with a flat lens as some Councils have done to existing fixtures. Lower image: The "flower-pot" mercury vapour lamps are a very bad choice. They are pervasive in residential streets throughout the metropolitan area and are especially glarey, inefficient and costly to run (they have been outlawed in other countries). A far better choice would a full-cutoff fitted with a sodium lamp or metal halide lamp.
Intended to highlight advertising or "enhance" architecture, these light fixtures indiscriminately spray light everywhere. Left: Billboard and business lighting, or lighting that is supposed to illuminate significant architecture, are often placed so that a substantial portion of the light completely misses its target and adds to the waste light and sky glow. Billboards should be illuminated from overhead light fixtures and buildings should be illuminated by carefully designed and aimed "spotlights". Both should be subject to curfews in late hours. Right: Globe lights may look good in the daytime, but are very wasteful at night because most of their light goes sideways and up into the sky! They should never be used for street lighting. Efficient, alternative designs are available where aesthetic lighting is required.
Good lighting practice
Examples of Good and Bad Lighting Practices in Adelaide
All images and illustrations by Martin Lewicki unless stated otherwise.