How To Calculate BUG Road Lighting Glare
Though BUG (IES TM-15-11, Addendum A) is
quite hard to do, it is easy to understand, it gives you numbers for the
"amount of light", wasted in various non-useful directions.
Light issuing from High to
Very High (H and VH) zones can cause glare from a distance and is anyway
wasted light. These zones, both foward and back are used for the G rating.
These are the red areas in the schematic below:
The blue areas in the image above (Upper Low and Upper High) show the zones where light is wasted skywards, allowing jet passengers to have a pretty view of the city below, but not much good to road users. It is best to have most light in the Foward Low and Forward Medium zones, which shine light onto the road surface relatively close to the luminaire. These areas are green in the diagram above. FL and FM zones are not used in the calculation, they are not zones of wasted light. So with the idea that it is a measure of waste, high numbers are considered bad, and low numbers are considered good:
A good mnemonic
would be: "It BUGs me all this waste!".
Here is another
example :
In the above example
13.7% of the light is wasted in the Uplight, hence the U5 rating. The
B2 and G2 ratings are not brilliant either.
When evaluating
a BUG rating the BL and UL zones are not used, because these are considered
to be useful light which shines down onto the road or sidewalk. The BL
and UL zones in the above example are at the bottom of the circular diagram,
from 30° to 30°.
Compare the above rating to this one:
Notice how no
light is wasted into the sky, none is wasted shining light far away (the
zones between 60° and 90° back and front). As a result the BUG
rating is much better, B1 U1 G0.
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ReplyDeletePendant Lights
Thank you for the explanation above.
ReplyDeleteWhich program are you using for BAG calculation based on an IES file?
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DeleteThank you so much for providing much needed information about roadway and highways and benefitting their usages looking for more.
ReplyDeleteRoadway Lighting and Highway lighting
Your welcome!
DeleteOoops. You're Welcome!
DeleteWell written for easy understanding
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