CLD Outdoor Lighting 3 — Questions and Answers
Question 1: The Dark Sky Association's five-zone system (E0–E4) is based on which primary environmental characteristic?
- Distance from the nearest city center
- Ambient nighttime brightness of the surrounding environment (Correct answer)
- Annual precipitation affecting sky clarity
- Number of street lights per square mile
Correct answer: Ambient nighttime brightness of the surrounding environment
The IDA/IES Model Lighting Ordinance environmental zones E0–E4 are defined by the existing ambient brightness of the nighttime environment, from pristine dark sky (E0) to urban core (E4).
Question 2: Which performance metric is most relevant when evaluating an outdoor LED fixture's resistance to photometric degradation in a coastal, salt-air environment?
- IP66 ingress protection rating (Correct answer)
- IK impact resistance rating
- NEMA 3R rating
- UL 1598 listing
Correct answer: IP66 ingress protection rating
IP66 (dust-tight + high-pressure water jets) indicates a sealed optical chamber that resists salt-air corrosion and condensation, which is critical in coastal environments.
Question 3: When designing parking lot lighting, the IES RP-20 recommends horizontal illuminance calculations at which plane?
- 1.0m above finished grade (task plane)
- 0.0m — finished grade (ground plane) (Correct answer)
- 0.5m above finished grade (bumper height)
- 1.8m above finished grade (eye level)
Correct answer: 0.0m — finished grade (ground plane)
IES RP-20 specifies horizontal illuminance for parking facilities measured at grade (0m), the surface where vehicles and pedestrians interact.
Question 4: A designer wants to minimize the ecological impact of a bridge lighting installation on bat populations. Which practice is most effective?
- Use blue-rich LEDs to improve visibility for bats
- Direct all light strictly downward and reduce intensity along bat flight corridors (Correct answer)
- Install strobe lighting to deter bats from the structure
- Maximize uniformity across the bridge deck
Correct answer: Direct all light strictly downward and reduce intensity along bat flight corridors
Bats rely on dark corridors for navigation and foraging; directing light strictly downward and keeping bat flight paths unlit preserves these ecological corridors.
Question 5: In roadway lighting design, 'veiling luminance' primarily affects driver vision by:
- Reducing perceived contrast of objects on the road ahead (Correct answer)
- Improving depth perception at intersections
- Increasing adaptation time when entering lit areas
- Enhancing color rendering of road markings
Correct answer: Reducing perceived contrast of objects on the road ahead
Veiling luminance superimposed on the retina by bright glare sources reduces the perceived contrast between an object and its background, reducing visibility.
Question 6: Which mounting configuration is typically used for sports field floodlights to achieve the highest uniformity across a rectangular playing field?
- Single central pole at midfield
- Four corner poles with symmetrical aiming (Correct answer)
- Continuous linear perimeter strip lighting at low mounting height
- Two poles on opposite end lines only
Correct answer: Four corner poles with symmetrical aiming
Four-corner pole configurations with symmetrically aimed floodlights provide the most uniform overlapping coverage across a rectangular field, as recommended by IES RP-6.
Question 7: What is the key advantage of using a modular LED engine design in outdoor area luminaires for a large municipal project?
- Lower initial fixture cost compared to traditional HID
- Ability to replace only the LED module at end-of-life without replacing the full fixture housing (Correct answer)
- Higher initial lumen output than a single monolithic LED
- Elimination of the need for photometric testing
Correct answer: Ability to replace only the LED module at end-of-life without replacing the full fixture housing
Modular LED engines allow the city to replace only the light source component when it reaches L70, avoiding costly full-fixture replacement and reducing long-term maintenance costs.
CLD Outdoor Lighting 3
The Dark Sky Association's five-zone system (E0–E4) is based on which primary environmental characteristic?