MODEL LIGHTING ORDINANCE - USER ’ S GUIDE MODEL LIGHTING ORDINANCE -
TEXT
PRESCRIPTIVE METHOD ( cont .) - User ’ s Guide LIMITS TO OFFSITE IMPACTS
The prescriptive method of the MLO restricts uplighting , including upward light emitted by decorative luminaires . A jurisdiction may choose to preserve some types of lighting , including lighting of monuments or historic structures . In this case , the adopting jurisdiction should exempt or otherwise regulate these types of lighting carefully so that it does not inadvertently allow glaring or offensive lighting systems .
Offsite effects of light pollution include glare , light trespass , sky glow , and impacts on the nocturnal environment . All of these are functions of the fixture or luminaire design and installation . This document replaces the previous luminaire classification terminology of full cut-off , semi cut-off , and cut-off because those classifications were not as effective in controlling offsite impacts as with the new IESNA luminaire classification system as described in TM-15-07 .
IV . NON-RESIDENTIAL LIGHTING ( cont .) - Ordinance Text
2 . Limits to Off Site Impacts
PRESCRIPTIVE METHOD
All luminaires shall be rated and installed according to Table C .
3 . Light Shielding for Parking Lot Illumination All parking lot lighting shall have no light emitted above 90 degrees .
Exception : a ) Ornamental parking lighting shall be permitted by special permit only , and shall meet the requirements of Table C-1 for Backlight , Table C-2 for Uplight , and Table C-3 for Glare , without the need for external field-added modifications .
A traditional method of defining light trespass is to identify a maximum light level at or near the property line . However , this method does not address offensive light that is not directed toward the ground , or the intensity of glaring light shining into adjacent windows . The requirements defined in Table C limit the amount of light in all quadrants that is directed toward or above the property line . The Backlight / Uplight / Glare ( BUG ) rating will help limit both light trespass and glare . ( A detailed explanation of the BUG system is provided in the section on Table C .)
The limits for light distribution established in Table C ( for the BUG rating system ) prevent or severely limit all direct upward light . A small amount of uplight reflected by snow , light-colored pavement or a luminaire ' s supporting arms is inevitable and is not limited by the prescriptive method of this ordinance .
Page B-14
USER ’ S GUIDE - Page 14 ORDINANCE TEXT - Page 14
Appendix B : Model Lighting Ordinance