Illuminating Insights
Advanced Lighting Impact Analysis (ALIA)
Read on for John's thoughts on a modern approach to evaluating outdoor lighting impacts!
John Petty, LC, MIES Sales Director - Roadway and Infrastructure
What is ALIA, and why is it being proposed?
ALIA stands for Advanced Lighting Impact Analysis. It’s a conceptual evolution of the current IES TM-15 BUG (Backlight, Uplight, Glare) rating system. While BUG provides a simple classification for outdoor luminaires, it has limitations in assessing real-world environmental and visual impacts. ALIA introduces a more holistic, context-aware scoring system to better evaluate outdoor lighting performance, aiming to minimize skyglow, protect ecosystems, and improve human visual comfort.
What are the main shortcomings of the existing BUG system?
There are five main shortcomings I attribute to the existing BUG system. These include:
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Lab-based ratings: BUG relies on lab measurements, which don’t always reflect real-world conditions like tilt or mounting height.
Measurement inconsistencies: Stray light and lab variability can lead to inconsistent ratings.
Misleading zero ratings: A U0 rating doesn’t guarantee zero uplight; minimal upward light may still exist.
Luminaire-centric: BUG focuses on the fixture, not the entire installation context.
Limited skyglow analysis: It ignores spectral factors like Scotopic-to-Photopic (S/P) ratio, which influence skyglow.
How would ALIA improve upon BUG?
ALIA introduces categorized scoring (0–5 scale) for Backlight, Uplight, Skyglow, and Glare. It also contains contextual analysis through incorporating environmental zones (E0–E4 or LZ0–LZ4) for tailored thresholds. Expanded metrics are introduced through the addition of vertical illuminance for light trespass, ULR for uplight, S/P ratio for skyglow, and TI for glare. Compared to BUG, ALIA has a clear methodology and weighting factors for adaptability and trust, as well as futureproofing with the consideration of spectral content and installation-level performance for emerging technologies like tunable LEDs.
What are the four core metrics of ALIA?
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Backlight (Vertical Illuminance – Ev): Measures light trespass at property lines or windows.
Uplight (Upward Light Ratio – ULR): Quantifies light emitted above the horizontal plane.
Skyglow (ULR + S/P Ratio): Combines uplight and spectral content to assess night-sky brightness impact.
Glare: Measured using Threshold Increment (TI) for driver visibility. These metrics are adjusted based on environmental zones
(E0–E4 or LZ0–LZ4).
How would ALIA handle environmental sensitivity?
ALIA uses CIE Environmental Zones (E0–E4) or IDA Lighting Zones (LZ0–LZ4) to set zone-specific thresholds. For example, E0 (wilderness) demands zero uplight and no measurable light trespass, while E4 (urban centers) allows higher limits. This ensures contextually appropriate recommendations.
How would the scoring system work?
Each metric is scored on a 0–5 scale, with scores tailored to environmental sensitivity, ensuring context-appropriate evaluations.
5 (Excellent): Exceeds stringent requirements.
3 (Good): Meets zone-specific limits.
0 (Unacceptable): Grossly exceeds limits.
Can you give an example of ALIA scoring?
For a rural zone (E2/LZ2), a design with 1.5 lux backlight, 1.8% uplight, 3000K color temperature, and TI of 9% might score 3 (Good) across categories—compliant but with room for improvement.
Yes! Tools like AGI32 and Visual Lighting can calculate key metrics (TI, ULR, Ev) and support compliance with standards like CIE 150:2017 and EN 13201. AGI32 offers advanced features for spectral analysis and atmospheric modeling, making it particularly strong for skyglow assessment.
Can current lighting software support ALIA?
This is purely a conceptual tool that’s open to feedback and refinement—my goal is to provide a transparent, adaptable, and comprehensive framework for evaluating outdoor lighting installations, promoting dark-sky protection, ecological responsibility, and improved visual performance.
How should the industry view ALIA today?
Find outdoor lighting solutions from Acuity Brands Lighting
Meet John
John is the Director of Sales for Infrastructure and Roadway at Acuity Brands and brings 44 years of electrical industry experience, including 29 years with Holophane Lighting and 15 years with Westinghouse Electric. He has been deeply involved with the IES, serving as past President of the Omaha Section, a Board Member for the Street and Area Lighting Conference (SALC), a member of the SALC Education Committee, and an instructor for the 8‑Hour Roadway and Parking Basics course. John has also served as an Advisory Vendor Member of the MSSLC, a member of the IESNA Roadway Lighting Executive Committee, Chair of the Streetlight Subcommittee (now RP‑8‑25 Chapter 11), Co‑Chair of the Measurements and Calculations Subcommittee (now RP‑8‑25 Chapter 3), and an advisor to the IESNA Emerging Professional Committee. A graduate of the University of Nebraska–Lincoln and an LC certificant through the NCQLP, he also helps teach the IESNA FOL‑09 and ED150 courses for the local section.