Crime, Safety and the Social Justice Aspects of Light Pollution

This blog post draws heavily on “The State of the Science” report by John Barentine, available here.

Summary

The belief that outdoor lighting improves traffic safety and discourages or prevents crime is common. It may explain in part the rapid growth in the use of outdoor light at night in recent years and decades. There are cases where the careful application of outdoor lighting may improve night-time safety, but there is no general benefit supported by scientific evidence.

Crime, Safety and Traffic

There is conflicting research on this topic and no consensus that adding or increasing lighting reduces crime, or traffic accidents, (except on busy urban junctions, where sensible lighting is shown to reduce accidents.)

Researchers have not been able to accurately predict or model the way that lighting might affect actual crime figures.  There are issues with the scientific reliability and honesty of that show a reduction in crime rates where lighting is installed, e.g. one study concluded that putting additional lighting did reduce crime, but the researchers failed to report that in those areas, additional policing was also implemented, which was not in the areas with no or low lighting.

Confounding factors and variables have subtle effects on research that add up to important, erroneous conclusions because responsibility can easily be assigned to lighting even though it contributed very little.  As a result, many of the claims about outdoor lighting and its impact on crime and traffic safety – for better or worse – may be fundamentally wrong (266, 267).

The Hazards of Glare

Glare from bright artificial light sources can decrease night-time safety.  Intense light directly entering the eye from unshielded sources scatters inside the observer’s eye, reducing the contrast between foreground and background and reducing peripheral and night vision.  Additionally, the pupil of the observer’s eye contracts, reducing total visibility by dimming the appearance of the entire scene. These effects make it difficult to see objects, such as cars or potential attackers, as distinct from what surrounds them.

Are We Afraid of the Dark?

Although the data on crime statistics is variable, how we feel about crime in relation to the darkness is not.  People in Western, urban societies tend to feel safer when there is more light, but how much more is needed for this effect?  The amount of light used in outdoor spaces at night may not reflect public expectations for feelings of safety and comfort (270), and artificial light itself may influence the human perception of fear (271). In some cases, over-lighting can itself become the source of safety hazards (272). However, properly designed lighting can reduce light pollution and save energy without compromising on public feelings of safety in outdoor spaces at night (273).

Conclusions for Crime and Safety.

The assumption that adding bright lights reduces crime is not supported by evidence.  However, adding appropriate, sensible, thoughtful lighting does reduce our fear of crime at night, and also reduces the obvious safety issue of glare.

Lighting and Social Justice

We know very little about how light pollution affects people in social contexts. Light at night may be used in ways that affect neighbourhoods according to the race of the people who live in them. That may make light at night use a matter of social and environmental justice.

Light Pollution, Racism and Poverty

The only comprehensive study to date on this topic looked at the social aspects of lighting in the U.S. only (292). Researchers found that Americans of Asian, Hispanic and Black descent tend to live in brighter neighbourhoods (Figure 7). In these areas, skyglow is about twice as Figure 7. Average exposure to light pollution in the continental United States by racial/ethnic group. The bars show population-weighted average zenith night sky brightness levels in units of millicandelas per square meter. Figure 4 in Nadybal, Collins and Grineski, 2020 (292). high as in predominantly white neighbourhoods. They further note that lower socioeconomic status is also associated with higher night-time light exposures. These conditions can add to other social and environmental stressors such as poverty and exposure to air and water pollution, affecting quality of life.

Closely related to this is the idea that light pollution is harmful to people whose religious or cultural practices rely on access to the night sky. The erasure of the stars from view due to skyglow separates people from this resource. Some argue that it threatens Indigenous traditions and knowledge systems based on accessibility of the natural night sky (300).

References

  • Marchant, P. Why lighting claims might well be wrong. International Journal of Sustainable Lighting, 19(1):69–74, jun 2017. doi: 10.26607/ijsl.v19i1.71.
  • Marchant, P. Do brighter, whiter street lights improve road safety? Significance, 16(5):8–9, oct 2019. doi: 10.1111/j.1740-9713.2019.01313.x.
  • Svechkina, A., Trop, T. and Portnov, B.A. How much lighting is required to feel safe when walking through the streets at night? Sustainability, 12(8):3133, apr 2020. doi: 10.3390/ su12083133.
  • McGlashan, E.M., Poudel, G.R., Jamadar, S.D., Phillips, A.J.K. and Cain, S.W. Afraid of the dark: Light acutely suppresses activity in the human amygdala. PLOS ONE, 16(6): e0252350, jun 2021. doi: 10.1371/journal.pone.0252350
  • Marchant, P., Hale, J.D. and Sadler, J.P. Does changing to brighter road lighting improve road safety? multilevel longitudinal analysis of road traffic collision frequency during the relighting of a UK city. Journal of Epidemiology and Community Health, 74(5):467–472, mar 2020. doi: 10.1136/jech-2019-212208.
  • Saad, R., Portnov, B.A. and Trop, T. Saving energy while maintaining the feeling of safety associated with urban street lighting. Clean Technologies and Environmental Policy, 23 (1):251–269, nov 2020. doi: 10.1007/s10098-020-01974-0.
  • Nadybal, S.M., Collins, T.W. and Grineski, S.E. Light pollution inequities in the continental united states: A distributive environmental justice analysis. Environmental Research, 189: 109959, oct 2020. doi: 10.1016/j.envres.2020.109959.
  • Hamacher, D.W., de Napoli, K. and Mott, B. Whitening the sky: light pollution as a form of cultural genocide, 2020.
a 15 second exposure showing the behaviour of insects around artificial lights. Image: Nevit Dilman It is dark and there is a streetlight attracting insects to it. Because it is a long exposure you can see the trails the insects make as they travel towards and around the light.

Environment

Human Health

Light pollution, especially the blue part of the spectrum of artificial light at night, is detrimental to human health. It is strongly linked to a variety of health issues, including heart disease, strokes, diabetes and cancer. Read More…

Sleep and Light Pollution

For billions of years, all life has relied on Earth’s predictable rhythm of day and night. It’s encoded in the DNA of all plants and animals. Humans have radically disrupted this cycle by lighting up the night, disrupting our own sleep patterns, causing a variety of health issues. Read More…

Wildlife and Eco-Systems

Plants and animals depend on Earth’s daily cycle of light and dark rhythm to govern life-sustaining behaviors such as reproduction, nourishment, sleep and protection from predators.  Scientific evidence suggests that artificial light at night has negative and deadly effects on many creatures including amphibians, birds, mammals, insects and plants. Read More…

Climate Change and Wasted Energy

Carbon emissions can be reduced if we turn off lights that we don’t use at night, or if we install timers or motion sensors.  These are ways to reduce light pollution, and reduce climate change that we can do today. Wasted light = Wasted energy = Wasted money. Read More…

Nocturnal Habitats and Wildlife.

Light pollution has many direct and indirect effects on our insect populations affecting almost every part of their lives. Changes are seen in mating, feeding, navigating, development and even their ability to hatch at the correct time. Two-thirds of invertebrates are partially or completely nocturnal, and even diurnal species can be impacted by the loss of their night. The situation is so serious that light pollution is reducing the nocturnal pollinator visits to flowers by 62% in some areas.  To find out more, head over the Buglife website.  There are many great people working on improving ways that light pollution affects the environment, here are just a few for you to check out.

Commission for Dark Skies.

CPRE (Council for the Preservation of Rural England)

Light Pollution Can Harm Wildlife

Light Pollution Wastes Energy & Money

The State of The Science

There is tons of research regarding how light pollution affects the environment, human health and habitats. Head over to our research page if you want to explore the database, or if you prefer a simpler (but still detailed analysis), try the “state of the science” report.

 

Street Lighting May Enable Crime.

Do you want to be safer at night? More and more research seems to suggest that floodlighting streets with overly bright lights is NOT the way to go.

Fewer cars are broken into at night on roads with part-night lighting (PNL in this instance is where street lights are switched off between midnight and 5am.)

Dr Phil Edwards (LANTERNS project lead and LSHTM) said: “The reason we did this research is because many local authorities in the UK have introduced part-night lighting on quiet, urban residential roads and rural roads, which have very little use after midnight, to save energy costs and reduce carbon emissions.  However, safety concerns about this policy have been raised.  Our previous research showed that switching off street lights at night does not increase crime. This new study suggests switching off street lights between midnight and 6am may actually reduce some types of crime.”


https://www.ucl.ac.uk/news/2022/mar/street-lighting-may-enable-rather-hinder-street-crime


guests at Kielder Observatory in Northumberland watching the milky way.

Astronomy for Absolute Beginners

Roy Alexander BSc, FRAS, MInstP, is the Chair of DarkSky UK and Director of AstroVentures CIC and Battlesteads Observatory.

Getting Started

The milky way in Autumn over the roof of Battlesteads Observatory
Autumn Milky way over Battlesteads Observatory, Martin Kitching

First of all, make sure you are dressed warmly, because even in the summer it can get chilly at night. Secondly, once you’re outside you need to give your eyes time to adjust to the darkness and although this starts straight away you need to be outside for at least fifteen minutes to begin with. After half an hour your eyes should be adapted to the dark. If you look at your phone screen, or any other lights, you will lost some of your night vision so try not to. You can use a red-light torch at night because red light does not affect your night vision.

Naked-eye astronomy is a great way to start. Try to be sitting down on a garden chair, or lying down on something like a picnic blanket or trampoline. Things to try to spot as a beginner are; the Moon, planets and well-known star patterns like the Plough or Cassiopeia. You can download a guide using the link at the end of this page.

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: Dr Martin Kitching & Chris Duffy

With binoculars you should be able to spot two or three of the objects shown above, especially the double cluster, seven sisters and the Orion Nebula.

Buying Binoculars and Telescopes

Sir Patrick Moore’s advice on buying and using hand-held binoculars was to buy any that are “10×50”. This means a 10x magnification and 50mm diameter front lenses. You can spend anything from £25 to £2500 on binoculars, but if you go for a higher magnification you’ll have to buy a tripod too. Helios Fieldmaster 10×50 are very good, and Celestron have a wide range of astronomy binoculars.

There are many, Many, MANY types of telescopes and plenty of magazines and websites offering advice on which ones to buy. If you’re a beginner then your best bet is to buy the largest manual “Dobsonian” type that you can afford. One with between 5 to 8 inches aperture is a good start. (although anything with an aperture diameter larger than 10″ might be difficult to carry.) Rother Valley Optics and Tring Astronomy Centre have good online shops and are happy to chat with you if you’re not sure.

Weather

Being an astronomer in the UK requires a great deal of optimism and a good understanding of the weather. Our favourite weather website is “Clear Outside” because it gives a detailed overview of cloud cover and a couple of other things that are very useful to astronomers. Check it out, and make sure to set it to your location.

Astro Guides

If you have a pair of binoculars, or want to buy a pair (£25-50 is a good starting price for a beginner), then you should definitely download Steve Tonkin’s free monthly binocular guide.

For ease of use at night and to protect your night vision, download and print out this guide. This stargazing guide introduces some useful apps for your phone, gives you a checklist of beginner objects and a super-simple star chat on the reverse.


light from streetlights pours into a house on the staircase through a window

Sleep and Light Pollution

For thousands of years, humans have lived a 24-hour day marked by the rising and setting of the sun. We have evolved to respond to the blue parts of sunlight, regulating our waking and sleeping cycle. Most artificial light reduces our ability to see the starry night sky, but it also impacts our sleep-wake cycles, or circadian rhythms. These circadian rhythms are universal across bird, reptile, and mammal species

Unfortunately, in our modern day-to-day life, light pollution extends our “daytime” experience well past sunset, thanks to artificial lighting containing some fraction of blue light.

Sleep is Essential

Everyone is a big fan of a good night’s sleep, but as you can see, sleep is an essential part of your wellbeing and health.

Melatonin

Melatonin is a key chemical related to your circadian rhythm and is strongly linked to getting you ready for sleep.

In animals, melatonin plays an important role in the regulation of sleep–wake cycles.[18] Human infants’ melatonin levels become regular in about the third month after birth, with the highest levels measured between midnight and 8:00 am.[19] Human melatonin production decreases as a person ages.[20] Also, as children become teenagers, the nightly schedule of melatonin release is delayed, leading to later sleeping and waking times.[21]

Wikipedia

Blue light prevents your body from making melatonin which can cause insomnia or prevent you falling asleep at the right time.

Light Pollution and Sleep – The Science Bit.

Think of a rainbow; can you remember all the different colours there are? We are interested in how the blue part of a light spectrum (or rainbow) affects our sleep. It turns out that the eye contains a part that is specifically for synchronising your circadian rhythm. These “ipRGC” cells react to blue light, and when they activate they send a signal to the brain that stops it producing melatonin. So if you want a good nights sleep, and if we want the animals in our habitats to sleep well, we MUST tackle the “blue light” part of our lighting at night.

For you, the best thing you can do is use a blue light filter, or “comfort filter” on your mobile phone. You can check the colour temperatures of your light bulbs and make sure they are less than 3,000K, the lower the better.  (Smart lights are great, e.g. Hue, because you can set them to any colour temperature you like, for example if you have Hue lights and a google hub you can say “Ok Google, set my lights to two thousand kelvin” – try it and see!) Research on melatonin suppression due to blue wavelengths of light is available if you click here.

Red Light and Sleep

There is some evidence suggesting that red, or redder lights at twilight and night can help you fall asleep, (although other evidence suggests its the absence of blue light that acts as a passive influence.)  In either case, your brain releases more melatonin as darkness falls and tends to release less when you’re exposed to blue light.  The bottom line is that we need to sleep in complete darkness, and to avoid as much exposure to light of all colours in the hour or so before we want to nod off.

The Milky Way and several dark sky objects such as Orion and the Pleiades over Battlesteads Observatory in Northumberland

 

The Milky Way and several dark sky objects such as Orion and the Pleiades over Battlesteads Observatory, illuminated with red light, in Northumberland. Image: Dr Martin Kitching

In a 2012 study on 20 female athletes, participants were randomly given 30 minutes of red light therapy every night for two weeks. When compared to the placebo group with no light therapy, the athletes had improved quality of sleep, melatonin levels, and performance. In 2019 a 3-week study of 19 people in an office environment showed that using a combination of red with the office white light in the afternoon improved afternoon alertness and circadian rhythms. There is growing evidence that red light plays a role in triggering melatonin production at night (maybe because we evolved over the centuries watching beautiful orange/red sunsets?)

Red Light and Sleep Inertia

The Angel of the North in Gateshead is viewed looking West on a cloudy day at sunset. A couple are sharing an intimate moment as they watch the sun set.

 

An Intimate Moment with The Angel of the North at Sunset by Roy Alexander

Sleep inertia is a sleepy feeling that you feel after you wake up. It can affect your short-term memory and alertness. A small 2019 study on sleep inertia showed that saturated red light delivered through closed eyelids, at levels that don’t suppress melatonin, may help ease sleep inertia when we wake up.

Social Justice and Light Pollution

In 2019 the government published the “Landscapes Review” (also known as the “Glover Report”) which was highly critical of successive governments’ inability to do “enough to protect nature or welcome diverse visitors, and extra government funding must help drive radical change”. Consequently one of the author’s recommendations is “Proposal 8: A night under the stars in a national landscape for every child”

Being able to visit dark sky areas in the UK requires time, money and transport. The lack of public transport, particularly at night means that people wanting to visit UK dark sky areas need to have a car. Consequently, families from disadvantaged areas of the UK and poorer backgrounds are under-represented in visitor numbers to our National Parks and AoNBs.

manchester trinity way light pollution
Trinity Way in Manchester. Image: Mark McNeill

In the USA there is a direct link between how “good” or “bad” urban community lighting is used in affluent areas compared to disadvantaged areas. Disadvantaged areas in the USA tend to be mainly non-white communities – a reflection of the social problems related to embedded racism in the USA system. A group of like-minded USA lighting experts have put together the “Light Justice” group, who seek to implement “…the practice of planning, designing, implementing, and investing in lighting for historically neglected communities through a process of stakeholder respect and engagement.” We need something like this in the UK to improve access to darker skies, for everyone. (Watch this space…)

Visit the Light Justice webpage here.

Watch a recording of an IDA advocates workshop about light pollution and social justice here.

You can find out more about social justice and light pollution by exploring our research database here using the search term “social justice”.

What’s the Solution?

The DarkSky UK continues to lobby the government to improve access to rural dark sky areas, but our main focus is to encourage towns and cities to apply for “Urban Night Sky” status for parks and green spaces.

Or go one step further and turn your neighbourhood into a “Dark Sky Community” like the village of Moffat in Scotland!

If you want to find out how to start the dark sky application process and find support and advice with your application, then get in touch via our contact form.

Mobile Apps

Dark Sky meter App (iPhones)
The Award-winning Dark Sky Meter by DDQ helps you measure the night sky brightness with the press of a button. Get instant information about the night sky quality and contribute to creating a global map of sky darkness. See our Measuring Light Pollution page for more information.

Loss of the Night App (iPhones and Androids)
The Loss of the Night app turns your eyes into a light meter, allowing you to become a citizen scientist and report how bright the night sky is where you live! See our Measuring Light Pollution page.

F.lux (available for Mac OS/X, Windows, Linx, iPhones and iPads)
f.lux is a colour temperature app that makes the colour of your computer’s display adapt to the time of day, warm at night and like sunlight during the day. It makes your computer screen look like the room you’re in, all the time. When the sun sets, it makes your computer look like your indoor lights. In the morning, it makes things look like sunlight again.

Lux (Android phones free or paid versions)
Lux intelligently adjusts the brightness of your display based on the environment you’re in. It’s also able to adjust the screen temperature of your display automatically to make it appropriate for night usage. At sunset, you can have Lux automatically warm your display and switch to your Night profile. If you’re an astronomer, you can enable astronomer mode to cut out harsh white light.

Twilight (for smartphones or tablets)
The Twilight app makes your device screen adapt to the time of the day. It filters the flux of blue light emitted by your phone or tablet after sunset and protects your eyes with a soft and pleasant red filter. The filter intensity is smoothly adjusted to the sun cycle based on your local sunset and sunrise times.

Dark-Sky Activities to Enjoy at Home

Here are some great resources to enjoy the night sky, whether it be in your garden, through your living room window, or on a computer screen.  

Family Arts & Crafts

Contribute to Night Sky Citizen Science

Familiarize yourself with your night sky and contribute to important citizen science projects:

  • Globe at Night is your go-to international citizen-science program that people can do from their backyards at no cost.
  • Dark Sky Citizen Science Program offers three citizen science programs to measure how light impacts our view of the night sky as well as three projects to measure the diversity of life on Earth.
  • The Satellite Streak Watcher citizen science programs or on SciStarter
  • Loss of the Night as well as on a blog on SciStarter 
  • Dark Sky Meter is a phone app that acts like a Sky Quality Meter.

Virtual Tours

Can’t get out into the dark? Check out these options for exploring the night sky with virtual reality:

Press Release Example

This is an example of a post that has its category set to ‘Press Release’ and how it shows up in the press release section. Any new post can be set as ‘Press Release’ as well as any other categories.

Outdoor Lighting Basics

IDA-UK recognizes that we need good outdoor lighting at night, but any required lighting be used thoughtfully. To minimize the harmful effects of light pollution, lighting should

  • Only be on when needed
  • Only light the area that needs it
  • Be no brighter than necessary
  • Minimize blue light emissions
  • Eliminate upward-directed light

Glossary of Lighting Terms

Types of Light (The Science Bit…)

Most people are familiar with incandescent or compact fluorescent bulbs for indoor lighting, but outdoor lighting usually makes use of different, more industrial sources of light. Common light sources include low-pressure sodium (“LPS”), high-pressure sodium (“HPS”), metal halide, and, most recently, light-emitting diodes (“LEDs”).

LPS is an old technology that is no longer being manufactured. It was favoured for use around observatories and some environmentally sensitive areas. Narrow-band amber LEDs emulate the colour.

HPS is commonly used for street lighting in many cities. Although it still emits an orange-coloured light, its colouring is more “true to life” than that of LPS.

In areas where it’s necessary to use white light, two common choices are metal halide and LEDs. One of the advantages of LED lighting is that it can be dimmed. Thus, instead of always lighting an empty street or parking lot at full brightness, LEDs can be turned down or off when they aren’t needed and then brought back to full brightness as necessary. This feature both saves energy and reduces light pollution during the night.

Because of their reported long life and energy efficiency, LEDs are rapidly coming into widespread use, replacing the existing lighting in many cities. However, there are important issues to consider when making such a conversion. See our LED Practical Guide for more information.

Colour Matters

It is crucial to control upward-directed light, but we know that the colour of light is also very important. Some lights have large amounts of blue light in their spectrum. Because blue light brightens the night sky more than any other colour of light, it’s important to minimize the amount emitted. Exposure to blue light at night has also been shown to harm human health and endanger wildlife. IDA recommends using lighting that has a colour temperature of no more than 2,700 Kelvins.

Lighting with lower colour temperatures has less blue in its spectrum and is referred to as being “warm.” Higher colour temperature sources of light are rich in blue light. IDA recommends that only warm light sources be used for outdoor lighting.

several diagrams showing the light spectra of various types of artificial and natural light.
Sunlight vs L.E.D. vs Florescent Light Spectra Comparison