In regard to estimation and costing of public lighting, which of the following should be adequate to provide visibility that guarantees for the user the maximum safety and sufficient visual comfort?

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SSC JE Electrical 06 Jun 2024 Shift 2 Official Paper - 1

Answer 1

Adequate luminance levels are crucial for providing sufficient visibility to ensure safety and visual comfort in public lighting.
Other factors like uniformity of luminance, glare limitation, and optical guidance are important but secondary to ensuring the appropriate level of luminance.

Illumination Required for Different Purposes:

The human eye possesses a tremendous power of accommodation and it can work comfortably within an enormous range of illuminations.
For example, at full noon, the sun provides about 120,000 lm/m2, diffuse day-light near a window is of the order of 600 lm/m2 (value varying widely) and full moon-light gives 0.1 to 0.3 lm/m2.
For reading, usually, 20 to 30 lm/m2 is generally considered sufficient, though daylight illumination is much higher.
Some persons can read without much strain even when illumination is as low as 3 lm/m².
The illumination level in public areas should be around 50 - 60 lux.