Light Trespass – When is it objectionable and what you can do about it?

Properly selected and installed, outdoors fixtures should not put light directly up into the sky (uplight), nor on other people’s property (spill light) in objectionable levels and certainly not into their homes. (IESNA G-1-03 – 3.2)

As little as one lux has been shown to interfere with the normal hormonal response to the diurnal cycle of night and day. JF Duffy and CA Czeisler, “Effect of light on human circadian physiology”, Sleep Med Clin. 2009 June: 4(2): 165-177.

Reading by backyard spill light.

So pouring light into someones bedroom is not a small matter. However, light can be an irritant anywhere it is unwanted. People should not have to go through a daily process of covering and uncovering their windows – each night and day – because someone else is careless with their outdoors lighting.

How much light is objectionable?

The Obtrusive Lighting Committee of the Illumination Engineering Society of North America, performed a study of this question in which a collection of volunteers were asked to rate a number of lighting scenarios, (IESNA TM-11-00). While, predictably there was a range of responses among the participants, the committee established guidelines for objectionable spill lighting based on levels that the average participant found to be “Very objectionable” – level 4 on a five point scale.

What is deemed objectionable naturally depends, in part, on the ambient lighting level of the setting. Accordingly, guidelines were set for four different conditions ranging from intrinsically dark landscapes, such as national park (E1) through to dense urban areas with commercial activity and high levels of night time activity (E4). Between these extremes, low ambient light levels such as one might find in rural and suburban areas were classified as (E2) and medium levels, such as urban residential areas (E3).


Environmental Zone

Pre-Curfew Limitations*

Post-Curfew Limitations*

E1

1.0(0.10)

0.0(0.00)**

E2

3.0(0.30)

1.0(0.10)

E3

8.0(0.80)

3.0(0.30)

E4

15(1.50)

6.0(0.60)

*Lux (footcandles) values on a plane perpendicular to the line of sight to the Luminaire(s)

**Where safety and security are issues, nighttime lighting is needed. Such lighting should meet IESNA recommendations for the particular property being lighted. Lighting should be designed, however, to minimize light trespass.


It is a simple matter to determine whether this guideline is being exceeded, by taking a reading at the property line using a suitable light meter.

What you can do about light trespass.

If you are the victim, the first step is to bring it up with your neighbor. Tell them your concern and suggest a reasonable solution. Usually just installing a shield will do, though sometimes a new fixture or relocation of a fixture is required. You might refer them to the companion webpage to this one – a Good Lighting Neighbor.

If discussions don’t work, in a civilized urban setting there will be an ordinance that precludes such offenses and you can lodge a complaint with the code enforcement office. However, in most instances, in this state, there will be no such ordinance. (Cities known to have such ordinances are listed below.)

In that case, you should first write your city counsel representative and mayor to complain about the lack of an ordinance to protection people from lighting abuse and copy us at trespass@darkskyarkansas.com. Most cities don’t keep records of such complaints and copying us provides a basis to push for such ordinances when we can show a record of complaints over time.

Beyond making a complaint about the lack of an ordinance,  you will need to decide how important the problem is to you, weighted against the relationship you have with your neighbor. If a voluntary solution was not reached, the later is probably not much of a consideration. In any event, the only practical course forward, for most people, is to take he matter to judge Judy, which is to say file a claim in small claims court.

Here is a summary of how the small claims court works in Arkansas. The claims form is simple enough and can be obtained from the court clerk. If you want to consider taking such action, again email us at trespass@darkskyarkansas with contact information and a summary of your situation and we will discuss whether it seems a reasonable course of action in your situation and whether we can assist in getting spill-light measurements made for you to present as evidence.

An ordinance is obviously the better solution, but unless people complain we can’t realistically make that happen.

PS Email us if talking to your neighbor works as well. We would love to hear success stories.

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