--- title: "Ten factors for flood, street lighting, luminaires" subject: "Industrial Power Distribution and Illumination" chapter: 8 key: "semester_6/industrial_power_distribution_and_illumination:ten-factors-flood-street-luminaires" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/ten-factors-flood-street-luminaires site: BCT Engineering --- # Ten factors for flood, street lighting, luminaires Industrial Power Distribution and Illumination · Chapter 8: Outdoor Lighting Design - Asked in: 2070 Magh, 8 marks - Video: [ILLUMINATION ENGINEERING - PART - 15 - ROAD AND STREET LIGHTING DESIGN AND THREE PROBLEMS](https://www.youtube.com/watch?v=7hlH_SzScsA) — zenmurali Sachithanandam - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/ten-factors-flood-street-luminaires - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-8 ## Question State 10 factors to be considered while: a) Designing of flood lighting system b) Designing of street lighting system c) Selection of luminaries ## Short answer a) Flood design: surface size/reflectance, surrounding brightness, required lux, projector distance, beam spread, CU, DF, WLF, lamp type/wattage, glare. b) Street: road class, required E_av/uniformity, width, mounting height, spacing, arrangement, surface reflection, glare control, junctions, maintenance. c) Luminaires: light distribution, lamp type/efficacy, light output ratio, glare control, colour rendering, IP rating, mechanical strength, mounting, maintenance ease, cost. ## Answer #### a) Factors in designing a floodlighting system 1. Size and shape of the surface to be lit (area A). 2. Colour and reflection factor of the surface. 3. Brightness of the surroundings. 4. Required illumination level (lux). 5. Distance and location of projectors. 6. Beam spread of projectors (narrow, medium, wide). 7. Coefficient of utilisation / beam factor. 8. Depreciation (maintenance) factor. 9. Waste light factor (spill light). 10. Lamp type, wattage, efficacy and colour; glare to viewers and traffic; cost. #### b) Factors in designing a street lighting system 1. Class of road and density of traffic (vehicles and pedestrians). 2. Required average illumination/luminance. 3. Uniformity ratio (E_min/E_av). 4. Road width and number of lanes. 5. Mounting height of lamps. 6. Spacing between poles (S/h ratio). 7. Arrangement: single-side, staggered, opposite, central. 8. Road surface reflection (rough/smooth, dry/wet). 9. Glare control and luminaire distribution (cut-off type). 10. Junctions, curves, bridges; maintenance factor; energy cost and control (photocell, timer, dimming). #### c) Factors in selecting luminaires 1. Light distribution (direct, indirect, cut-off, beam spread). 2. Lamp type and efficacy (LED, HPSV, metal halide). 3. Light output ratio / efficiency of the fitting. 4. Glare control (shielding angle, diffusers, louvres). 5. Colour rendering and colour temperature. 6. Environment: IP rating against dust and water; flame-proof or corrosion-proof where needed. 7. Mechanical strength and heat dissipation. 8. Mounting method and aiming facility. 9. Ease of maintenance and cleaning. 10. Initial cost, life and running cost; appearance. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is a factor in designing a floodlighting system? A. Colour and reflection factor of the surface and brightness of surroundings B. Number of lanes and road width C. Ingress protection of a street luminaire only D. Uniformity ratio E_min/E_av of a road Answer: A. Floodlight design depends on surface reflectance and surroundings; lanes and uniformity ratio are for roads. (Key point: Floodlight design factor) 2. Which is a street lighting design factor? A. Waste light factor B. Class of road, traffic density and the S/h ratio C. Beam spread of projector D. Reflection factor of a building face Answer: B. Road class, traffic, uniformity ratio, width, height, S/h and arrangement are street factors. (Key point: Street lighting factor) 3. Which relates to selecting luminaires? A. Number of road lanes B. Waste light factor C. Light distribution, glare control and IP rating for the environment D. Length of the road Answer: C. Luminaire selection covers distribution, efficacy, glare control, IP rating, colour rendering and maintenance. (Key point: Luminaire selection factor) 4. In street lighting design, why is road surface reflection considered? A. It sets the cable size B. It sets the lamp colour only C. It determines the number of phases D. Rough/smooth and dry/wet surfaces reflect light differently, affecting the luminance seen by drivers Answer: D. Surface reflection affects perceived brightness, so it is a design factor. 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