Dobbins JLUS IMP Public Draft Light Pollution Study | Page 58
Terms that describe traditional lighting such as “Full Cutoff” and “Cutoff”
have been superseded with ratings from the BUG system in the Illuminating
Engineering Society (IES) technical memorandum, TM‐15‐2011, Luminaire
Classification System for Outdoor Luminaires. The following section explains
the BUG System.
BUG System
The BUG system rates a luminaire based on its absolute output, compared
to the relative requirements in the cutoff classification system and provides
three ratings based on their influence: a backlight rating (B), an uplight
rating (U), and a glare rating (G). Each rating is assigned a numerical value
ranging from 0 to 5 based on the luminaire output. The diagram to the right
provides a visual explanation of the components of the BUG system.
5. Overview of Lighting Regulations
portion of light behind the pole, so B ratings are designated based on the
location of the luminaire with respect to the property line. A high B rating
luminaire maximizes the spread of light, and is effective and efficient when
used far from the property line. When luminaires are located near the
property line, a lower B rating will preven t unwanted light from interfering
with neighboring properties.
The following graphic illustrates these different distribution zones of the
BUG rating system.
The three components of BUG ratings are defined as follows.
Backlight ‐ creates light trespass onto adjacent sites. The B rating takes into
account the amount of light in the BL, BM, BH and BVH zones, which are in
the direction of the luminaire OPPOSITE from the area intended to be
lighted.
Uplight ‐ causes artificial sky glow. The lower uplight (zone UL) causes the
most skyglow and negatively affects professional and academic astronomy.
Upper uplight (UH) not reflected off a surface is mostly energy waste. The
U rating defines the amount of light into the upper hemisphere with greater
concern for the light at or near the horizontal angles (UL).
Glare ‐ can be visually disabling. The G rating takes into account the amount
of frontlight in the FH and FVH zones as well as backlight in the BH and BVH
zones.
In general, a higher BUG rating means more light is allowed in solid angles,
and the rating increases with the lighting zone. However, a higher B
(backlight) rating simply indicates that the luminaire directs a significant
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DRAFT Dobbins Air Reserve Base Light Pollution Study
March 2018