Lighting, Crime & Safety

There is no clear scientific evidence that increased outdoor lighting deters crime and in some cases increased outdoor lighting actually increases crime.

A 2015 study published in the Journal of Epidemiology and Community Health found that streetlights don’t prevent accidents or crime, but do cost a lot of money. The researchers looked at data on road traffic collisions and crime in 62 local authorities in England and Wales and found that lighting had no effect, whether authorities had turned them off completely, dimmed them, turned them off at certain hours, or substituted low-power LED lamps.

According to the 2015 study, “[W]hen risks are carefully considered, local authorities can safely reduce street lighting saving both costs and energy … without necessarily impacting negatively upon road traffic collisions and crime.” In fact, most property crime occurs in the light of the day. And some crimes like vandalism and graffiti actually thrive on night lighting.

A 2011 study of London street lighting and crime, showed that there is no good evidence that increased lighting reduces total crime.” A 1997 National Institute of Justice study concluded, “We can have very little confidence that improved lighting prevents crime.”

The truth is bright, glaring outdoor lighting can increase crime and decrease safety by making victims and property easier to see. A Chicago Alley Lighting Project showed a correlation between brightly lit alleyways and increased crime.

Streetlight Glare

Photo by Jim Richardson.

Brighter Does Not Mean Safer:

According to a 2012 AMA report, “Glare from nighttime lighting can create hazards ranging from discomfort to frank visual disability.”

Outdoor lighting is intended to enhance safety and security at night, but too much lighting can actually have the opposite effect. Visibility should always be the goal. Glare from bright, unshielded lights actually decreases safety because it shines into our eyes and constricts our pupils. This can not only be blinding, it also makes it more difficult for our eyes to adjust to low-light conditions.

The Solution? The Right Type of Light Used in the Right Way at The Right Time

Lighting that is the correct type, correct brightness, pointed and switched on only where you need it, is the solution. Why not become a member of the IDA-UK to find out more?

Night Sky Heritage

The nighttime environment is a precious natural resource for all life on Earth, but the glow of uncontrolled outdoor lighting has hidden the stars and changed our perception of the night.

“For my part I know nothing with any certainty, but the sight of the stars makes me dream.”

— Vincent van Gogh

The Natural Night Sky Inspires

Until recently, for all of human history, our ancestors experienced a sky brimming with stars – a night sky that inspired science, religion, philosophy, art and literature, including some of Shakespeare’s most famous sonnets.

The natural night sky is our common and universal heritage, yet it’s rapidly becoming unknown to the newest generations.

Van Gogh painted his famous “Starry Night” in Saint Rémy, France, in 1889. Now, the Milky Way can no longer be seen from there. If he were alive today, would he still be inspired to paint “Starry Night”?

Experiencing the night sky provides perspective, and inspiration, and leads us to reflect on our humanity and place in the universe. The history of scientific discovery and even human curiosity itself is indebted to the natural night sky.

Without the natural night sky we could not have:

  • Navigated the globe
  • Walked on the Moon
  • Learned of our expanding universe
  • Discovered that humans are made of stardust
Some examples of dark sky objects you can see and image in a dark sky site.
Deep sky objects that are visible at a proper dark sky site. Image: A montage by Chris Duffy & Dr Martin Kitching

International Dark-Sky Places Program

For these reasons, IDA established the International Dark Sky Places Program in 2001 to recognise excellent stewardship of the night sky. Designations are based on stringent outdoor lighting standards and innovative community outreach.

Since the program began, more than one hundred Parks, Communities, Reserves, and Sanctuaries have received International Dark Sky Place designations.

Human Health

Exposure to Light Pollution Harms Your Health

Research suggests that light pollution negatively effects human health, increasing risks for obesity, depression, sleep disorders, diabetes, breast cancer and more.

Many species (including humans) need darkness to survive and thrive.

— American Medical Association Council on Science and Public Health (2012)

Circadian Rhythm and Melatonin

Like most life on Earth, humans have a biological clock called your circadian rhythm. It is a sleep-wake pattern governed by the day-night cycle. Artificial light at night disrupts that cycle.

Our bodies produce the hormone melatonin in response to our circadian rhythm. Melatonin helps keep us healthy. It induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes and adrenal glands. Nighttime exposure to light pollution suppresses melatonin production.

Blue Light is the Most Harmful Type of Light Pollution

Exposure to blue light at night is harmful. Unfortunately, most LEDs used for outdoor lighting — as well as computer screens, TVs, and other electronic displays — have a white colour which is dominated by blues.

According to experts at Harvard Medical School,

“If blue light does have adverse health effects, then environmental concerns, and the quest for energy-efficient lighting, could be at odds with personal health. ”

A 2016 American Medical Association report expressed concern about exposure to blue light from outdoor lighting and recommends shielding all light fixtures and only using lighting with 3000K colour temperature and below.

To minimize harm from blue light in your home, choose the right light bulb and download a colour temperature app that adapts your electronic screen to the time of day – cool light during the day and warm light at night.

Colour Temperature Apps:

  • F.lux is available for Mac OS/X, Windows, Linx and (jailbroken) iPhones and iPads.
  • For those with Apple devices using the iOS 9.3 operating system and above, the Night Shift app is pre-installed. Click here to learn how to use it. 
  • Lux is available for Android devices free or for pay.
  • Twilight is available for smartphones or tablets.

Choosing the Right Bulb


In this picture both lights are “white” but the bulb on the left is rich in blue light, while the one on the right isn’t. The warmer light on the right is the better, healthier one to choose.

All packaging for new light bulbs provides colour temperature information. Use low-colour temperature light sources for interior and exterior light. Their light is less harsh and less harmful to human health and the environment. Look for warm white sources with a colour temperature of 3000K or lower.

Kelvin Temperature Scale

Higher colour temperatures mean white light that is more blue-ish and less warm, the kind that should be avoided after dusk.

3 types of light bulbs showing different effects of colour temperatures.
Image: Wikipedia, shows three different white lights with blue, yellow and orange tints to them. The orange 2700K light is the healthiest and most environmentally positive type to chose.

Glare from Bad Lighting is a Safety Hazard

Glare from poorly shielded outdoor lighting is also harmful to your health because it decreases vision by reducing contrast. This limits our ability to see potential dangers at night. Ageing eyes are especially affected.

“Glare from nighttime lighting can create hazards ranging from discomfort to frank disability.”

American Medical Association Council on Science and Public Health (2012)

Measuring Light Pollution

Jesus Acosta, the impact of light pollution as seen during a power outage.

Due to light pollution, the night sky over many of our cities is hundreds of times brighter than a natural, starlit sky. This skyglow hides the stars from our sight and prevents us and all life on Earth from experiencing a natural night, even in areas hundreds of miles away from towns and cities.

How can you help?

Lincoln cathedral at night
Lincoln Cathedral. Image: Mark McNeill

Become a Citizen Scientist

The CPRE does an annual star count which you can do from your back garden or yard. Anyone can take part in it, and you don’t need specialist training or equipment. Find out more here.

Participating in the Globe at Night citizen-science campaign is a great way to help our understanding of skyglow and its impact. No special tools are required and observations can easily be reported by smartphone, tablet or computer.

It’s also possible to use your smartphone to make night sky brightness measurements. The Dark Sky Meter app makes use of the iPhone camera to record the brightness of the night sky, while the Loss of the Night app walks the user through the sky as measurements are made with a different sensitive tool – the human eye. It’s available for both Android devices and iPhones. And now, thanks to the MySkyatNight project, you can also do your own analysis of all this available data.

Jodrell Bank under a starry sky but with some light pollution showing in the background
Jodrell Bank under a starry but light polluted sky. Image: Mark McNeill

Another way you can help is by participating in the Cities at Night project, which relies on citizen scientists to map and identify photos of cities taken from the International Space Station. This valuable information helps researchers better assess light pollution across of the globe.

In addition to the smartphone apps and the Globe at Night project, more rigorous, long-term monitoring is also being conducted. The section below describes standards for collecting and reporting skyglow measurements.

How Can You Help With Skyglow Observations?

The introduction of the Sky Quality Meter and the International Year of Astronomy Lightmeter have led to a large number of permanent online skyglow monitoring stations. At the same time, a number of individuals and groups have developed their own non-commercial devices for measuring skyglow.

If there is a dark sky park or reserve near you, they are always on the lookout for volunteers to help them with their dark sky measurements.

a before and after picture showing how bad lighting can be improved using IDA guidelines
a before and after picture showing how bad lighting can be improved using DarkSky guidelines. Image: DarkSky