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ALL LIVING THINGS adjust their behaviour according to natural light. Man’s invention of artificial light has done much to enhance our night-time environment but, if not properly controlled, obtrusive light (commonly referred to as light pollution) can present serious physiological and ecological problems.

Obtrusive Light, whether it keeps you awake through a bedroom window or impedes your view of the night sky, is a form of pollution and can be substantially reduced without detriment to the lighting task.

Sky glow, the brightening of the night sky above our towns, cities and countryside, Glare the uncomfortable brightness of a light source when viewed against a dark background, and Light Trespass, the spilling of light beyond the boundary of the property or area being lit, are all forms of obtrusive light which may cause nuisance to others, waste money and electricity and result in the unnecessary emissions of greenhouse gases. Think before you light. Is it necessary? What effect will it have on others? Will it cause a nuisance? How can I minimise the problem?

Do not “over” light. This is a major cause of obtrusive light and is a waste of energy. There are published standards for most lighting tasks, adherence to which will help minimise upward reflected light. Organisations from which full details of these standards can be obtained are given on the last page of this leaflet. Dim or switch off lights when the task is finished. Generally a lower level of lighting will suffice to enhance the night time scene than that required for safety and security.

Use specifically designed lighting equipment that minimises the upward spread of light near to and above the horizontal. Care should be taken when selecting luminaires to ensure that appropriate units are chosen and that their location will reduce spill light and glare to a minimum. 

Remember that lamp light output in LUMENS is not the same as lamp wattage and that it is the former that is important in combating the problems of obtrusive light

Keep glare to a minimum by ensuring that the main beam angle of all lights directed towards any potential observer is not more than 70o. Higher mounting heights allow lower main beam angles, which can assist in reducing glare. In areas with low ambient lighting levels, glare can be very obtrusive and extra care should be taken when positioning and aiming lighting equipment. 

With regard to domestic security lighting the ILE produces an information leaflet GN02 that is freely available from its web site. 

The UK Government will be providing an annex to PPS23 Planning and Pollution Control, specifically on obtrusive light. However many Local Planning Authorities (LPA’s) have already produced, or are producing, policies that within the new planning system will become part of the local development framework. For new developments there is an opportunity for LPA’s to impose planning conditions related to external lighting, including curfew hours.

For sports lighting installations (see also design standards listed on Page 4) the use of luminaires with double-asymmetric beams designed so that the front glazing is kept at or near parallel to the surface being lit should, if correctly aimed, ensure minimum
obtrusive light.

 In most cases it will also be beneficial to use as high a mounting height as possible, giving due regard to the daytime appearance of the installation. The requirements to control glare for the safety of road users are given in Table 2.

When lighting vertical structures such as advertising signs direct light downwards, wherever possible. If there is no alternative to up-lighting, as with much decorative lighting of buildings, then the use of shields, baffles and louvres will help reduce spill light around and over the structure to a minimum. 

For road and amenity lighting installations, (see also design standards listed on Page 4) light near to and above the horizontal should normally be minimised to reduce glare and sky glow (Note ULRs in Table 1). In sensitive rural areas the use of full horizontal cut off luminaires installed at 0o uplift will, in addition to reducing sky glow, also help to minimise visual intrusion within the open landscape. However in many urban locations, luminaires fitted with a more decorative bowl and good optical control of light should be acceptable and may be more appropriate.

ENVIRONMENTAL ZONES:
It is recommended that Local Planning Authorities specify the following environmental zones for exterior lighting control within their Development Plans.

Where an area to be lit lies on the boundary of two zones the obtrusive light limitation values used should be those applicable to the most rigorous zone.

DESIGN GUIDANCE
The following limitations may be supplemented or replaced by a LPA’s own planning guidance for exterior lighting installations. As lighting design is not as simple as it may seem, you are advised to consult and/or work with a professional lighting designer before installing any exterior lighting.

ULR = Upward Light Ratio of the Installation is the maximum permitted percentage of luminaire flux for the total installation that goes directly into the sky.
Ev = Vertical Illuminance in Lux and is measured flat on the glazing at the centre of the window
I = Light Intensity in Cd
L = Luminance in Cd/m2
Curfew = The time after which stricter requirements (for the control of obtrusive light) will apply; often a
condition of use of lighting applied by the local planning authority. If not otherwise stated
23.00hrs is suggested.
* = From Public road lighting installations only

1. Upward Light Ratio – Some lighting schemes will require the deliberate and careful use of upward light – e.g. ground recessed luminaires, ground mounted floodlights, festive lighting – to which these limits cannot apply. However, care should always be taken to minimise any upward waste light by the proper application of suitably directional luminaires and light controlling attachments.
2. Light Trespass (into Windows) – These values are suggested maxima and need to take account of existing light trespass at the point of measurement. In the case of road lighting on public highways where building facades are adjacent to the lit highway, these levels may not be obtainable. In such cases where a specific complaint has been received, the Highway Authority should endeavour to reduce the light trespass into the window down to the after curfew value by fitting a shield, replacing the luminaire, or by varying the lighting level.
3. Source Intensity – This applies to each source in the potentially obtrusive direction, outside of the area being lit. The figures given are for general guidance only and for some sports lighting applications with limited mounting heights, may be difficult to achieve.
4. Building Luminance – This should be limited to avoid over lighting, and related to the general district brightness. In this reference building luminance is applicable to buildings directly illuminated as a night-time feature as against the illumination of a building caused by spill light from adjacent luminaires or luminaires fixed to the building but used to light an adjacent area.TI = Threshold Increment is a measure of the loss of visibility caused by the disability glare from the obtrusive light installation

5. Road Classifications as given in BS EN 13201
2: 2003 Road lighting Performance requirements
Limits apply where users of transport systems are subject to a reduction in the ability to see essential information. Values
given are for relevant positions and for viewing directions in path of travel. See CIE Publication 150:2003, Section 5.4 for
methods of determination. For a more detailed description and methods for calculating and measuring the above
parameters see CIE Publication 150:2003.

Martin Wainwright
Friday November 21, 2003
The Guardian

Over-anxious Britons are placing a blind, almost medieval, faith in brighter streetlamps and security lighting as crime deterrents, according to a statistical analysis which raises questions about Home Office research.

Government advice that surveys in Britain and the US show better lighting to have “no negative effects and demonstrable benefits for law-biding citizens” is flawed and unjustified, according to a study to be published in the British Journal of Criminology.

The paper follows arguments at the Home Office over a summary of research on street lighting and its effects on crime. Independent criticism of the summary’s use of statistics was initially expected to be incorporated as a “serious health warning” but appeared only as a brief addendum.

The scientist behind the criticisms, Paul Marchant, a statistician at Leeds Metropolitan University, said yesterday that the conclusions of the paper – The Effects of Improved Street Lighting on Crime; Home Office Research Study 251 – were unfounded and based on statistical mistakes.

“They have all the trappings of the right sort of official information, but they contain major errors. Not only does the paper fail to demonstrate that improved street lighting decreases crime, its figures could equally well show that it increases it.”

The row comes at a time of growing concern about light pollution, with a warning about its effects, particularly on astronomy, sounded last month in a report by the Commons select committee on science and technology.

Dr Marchant said that pressure for supposedly “crime-deterring” extra street lighting was worsening the problem, abetted by householders’ security lights whose effectiveness was also a matter of faith.

“It may not be too fanciful to make comparisons with our medieval ancestors’ measures against witchcraft – tokens hung over the door and so forth,” he said. “We know the ‘witches’ are out there, and we turn to deterrents which we think will scare them off. But we do not know. We do not have the evidence.

“Meanwhile light pollution has substantial environmental consequences. If any decision is taken to increase lighting, it needs to be taken on the best possible evidence.”

The Home Office said officials had been made aware of the issues and had asked the report’s authors to look at them in detail. A spokesman said: “The need for further analysis of statistical variance calculations was accepted and an addendum has been added to reflect this change. But this did not substantially affect the report’s conclusions.”

Researchers at a science conference in the US have produced more evidence to show how nighttime activity may increase the incidence of breast cancer. Their findings presented to the meeting of the American Association for the Advancement of Science in Denver suggest shift-workers may be particularly at risk from the disease. It adds further to the evidence already gathered on the subject by other researchers, particularly with data from Denmark. Theory suggests that bright light at night diminishes the body’s supply of melatonin – a hormone involved in the control of the body’s natural rhythms. This in turn may lead to an increase in levels of the female sex hormone estrogen, which has been linked to breast cancer. Researchers are looking into whether risks can be reduced by using different kinds of lighting.

In industrialized Western societies, breast cancer rates are extraordinarily high. One in every seven women in nations such as ours will get breast cancer. In developing countries, which do not have a prevalence of electric light breast cancer, rates among women are five times lower, he said.He said scientists were wondering whether light was a factor determining why blind women appeared to have a lower risk of breast cancer. Meanwhile women who travel over many time zones are more likely to get the disease.

Battle Ground School District in Clark County has reduced vandalism to almost zero with a policy to darken campus after 10:30 p.m. Spokane School District and Riverside School District have been experiencing similar results for over six years.

Is it possible to save energy and cut crime at the same time? According to school district experience, simply turning off the lights has cut vandalism. Sound preposterous? Experience shows that contrary to conventional law enforcement theory, which stresses well-lit areas, many districts had less vandalism once they’ve instituted a dark campus policy to save energy dollars. This is significant when you consider how much vandalism costs schools.

In 1980, California public schools lost approximately 13 million dollars from vandalism related acts during non-school hours, according to statistics collected by the State Department of Education.

One of the first school districts to reason that vandals get no thrill out of working in the dark was the San Antonio School District in Texas. In 1973 they started a night time black out program at 19 schools. Sam Wolf, Director of Security for the district says, “I remember as a kid, we never hung around in the dark. We hung around a street light or some other kind of illumination. We wanted to see who was with us. With vandalism, the thrill is seeing the windows broken, in seeing the words written on the wall. It is no thrill to hang around in the dark”.

Vandalism damage in the district was reduced from $160,000 in the late 1960’s to $41,000 per year. Also, “We saved so much on utilities that our business managers and everybody else were quite impressed,” says Wolf.

CALIFORNIA RESULTS

Bill Bakers, retired Associate Superintendent for the East Side Union High School District in San Jose, who pioneered an energy savings program that has saved over a million dollars per year, reports:

“We are not aware of any school districts where blacking-out campus coincided with an increase in vandalism, burglary, or arson. There has not been an increase of such incidents in our district during the hours of total blackness. It seems logical that a blackout discourages youth from entering campuses — they have as much fear of the unknown as anyone else. In case of burglars, any light shown on a campus is cause for suspicion on the part of neighbors and police.”

Don Rodriguez, former Energy Manager for Cupertino Union School District reported that vandalism decreased an additional 29% or $8,160 during 1981-82, when they instituted a dark campus policy, along with their antivandalism program, Project Pride. Project Pride rebates a percentage of the savings resulting from a decrease in projected losses due to vandalism. It also involves a variety of activities including weekly, monthly, and semiannual reports and graphs and charts on vandalism rates.

While the cause and effect between night time blackouts and a reduction in vandalism is not clear cut, no one has reported an increase in vandalism due to night time blackouts.

The Livermore Joint Unified School District has had a dark campus policy since 1974. Director of Facilities Maintenance, Rudy D’Ambra says:

“A dark campus policy positively will not increase vandalism. This is what many people are concerned about, including the police, but it did not happen. We’ve noticed a slight decrease in vandalism over the years, but we have done other things too, like vandal watches and Sonitrol.”

Energy Savings in his district were about ten percent after the first full year of the dark campus policy

Skyglow is the orange “smog” that hangs over all cities at night. It is caused by wasted light shining upwards, rather than downwards where we need it.

The image shows the excessive light pollution thrown out by large towns and cities, as seen from a rural location in South West England. The extent of the problem is highlighted by the fact that some conurbations can be detected from over 35km away.

Skyglow over suburbia

The offending lights are behind the raised horizon, but due to poor direction they light up the sky.

You can see the glow of the football floodlights for many miles, even though the photographer is over a hundred feet ABOVE the football ground. Note also the brightly and poorly lit Abbey. If the lights were properly directed, the target would be well lit, without the need to shine the lights into the sky.

Again, from altitude this offending town is spilling light upward, as seen by the reflection from the clouds. One of the worst light polluters in the South of England, the ferry terminal at Poole can be seen from many miles away due to its poorly directed lighting.

Again over 1/2 mile away and 100 feet or so above the complex, the actual

lights themselves are still visible. It makes you wonder whether they actually want to light the ground… Whilst all these locations show evidence of poor lighting, fortunately not everyone is so careless with their energy!

Many town, country and district councils, as well as some private businesses, have listened to the CfDS argument, and have made changes to their lighting policy which saves them energy (and therefore money), and also reduces the light pollution nuisance for the local population.

The vast majority of UK children have never experienced total darkness because parents surround them with artificial lights, a survey suggests. Even though a power company sponsors the research, it says that leaving the landing light off now and again might be better for their health. The national survey suggested that 98% of children do not sleep in total darkness. Most parents admitted that their children were never far from a source of artificial light – more than half said they left a hall or landing light on at night purely to comfort the child. One in three provides a night-light in their child’s bedroom. Powergen, which commissioned the research, said that leaving lights on at night costs Britain an enormous £468m a year. Its “energy efficiency manager”, Mike Newell, said: “Coupled with the effects of street lighting, many of our children will grow up without ever knowing what true darkness really is.” Doctors also say that sleeping in near or total darkness has its benefits. Dr Chris Idzikowski, director of the Sleep Assessment and Advisory Service, said: “By leaving lights on at night, parents believe they are comforting their children. “In actual fact, exposure to constant artificial light may reduce levels of melatonin, which regulates the body’s internal clock, and the Circadian cycle. “This could lead to a disruption of sleeping patterns, hyperactivity and may have a negative impact on a child’s health.” A third of parents surveyed said that they believed that children did not notice the change in light when the clocks go forwards or backwards.

Vandalism, burglary and robbery in Des Moines have dropped 3.5 percent.

June 5, 2004

A money-saving decision to turn off thousands of Des Moines street- lights met with dire predictions from critics who warned that darkened streets would create a haven for crime.

Statistics tell a different story.

The first four months of 2004 saw a 3.5 percent drop in vandalism, burglary and robbery, and “we’ve observed no significant increase in crime in the areas where the lights have been turned off,” Police Maj. Dale Patch said.

Cash-strapped city leaders last summer came up with a plan that would cut power to 39 percent of streetlights along major streets and save taxpayers an estimated $700,000 a year.

Seventeen percent of the city’s 23,376 streetlights went dark in September.

Concerned residents howled.

“Thieves don’t like light,” business owner Mike Kinter said last year. He said the move would set back crime prevention measures taken over the past 10 years.

Earlier this week, Kinter acknowledged that the darkness has had no noticeable effect, and said, “I understand both sides.”

Others remain unconvinced that the move was a good idea, no matter how much money it saves.

Dave Reed says it’s about convenience, not crime.

“The city in general is still well-lit enough that crime isn’t a problem,” said Reed, whose home near Drake University is across the street from one of the lights that was turned out. “You want to see where you are going when you have to go outside.”

When the issue first surfaced, Reed said he found the idea of turning out streetlights ridiculous. His opinion hasn’t changed.

“We expect the city to provide services for its taxpayers, services like police and fire and streetlights,” Reed, 45, said Wednesday night while he walked along University Avenue with his 7-year-old son Spencer and the family dog. “It’s still dark, and I’m still not happy about it.”

Evy Washington of Des Moines puts little faith in crime statistics. She takes courses at Des Moines Area Community College’s downtown campus and AIB College of Business just south of the loop and takes the bus home at night.

She’s convinced that darkness will invite trouble.

“A lot of things happen in the dark,” Washington, 40, said. “Things that maybe aren’t reported as crimes.”

Washington also wonders if taxpayers will ever see a benefit.

City officials “claim they want to save money, but I don’t know if that’s worth it,” she said.

The city’s traffic and transportation director, Gary Fox, said power has been returned to 170 of the darkened lights since September at the request of police officers, homeowners and business owners. All such requests must get city approval. A dozen came from police, most in the first three months.

One request came from elderly residents of the Hartford Manor apartment building at Southeast Sixth Street and Hartford Avenue.

The streetlight in front of the long, single-story building has been dark since last fall.

“We have one in a wheelchair, two with walkers, and it’s just too dark out there,” resident Neta Phillips said.

The tenants started a petition in April. Everyone signed. The city agreed to turn the light on.

So far, darkness remains.

“I’m glad to know they are going to turn it back on,” Phillips said. “But we are still waiting.”

Fox said some residents and business owners in areas where lights were turned out have complained about vandalism, burglary and other crime. Police and Fox point out that the statistics show no measurable increase since the lights went out.