Highway Lighting - IES Previous Year Questions

1. For a street lighting system, having the following conditions:

Street width = 15 m, mounting height = 7.5 m, lamp size = 6000 lumen, Luminaire type = II, coefficient of utilization = 0.44, maintenance factor = 0.8.  What is the spacing between lighting units to produce average lux = 6 ?

[IES 2021]

  1. 20 m
  2. 23 m
  3. 27 m
  4. 18 m 
Answer: Option B
Explanation:
The spacing between the lighting units =
Lamp lumen x Utilization factor x Maintenance factor / Average lux x Width of the road

=
6000 x 0.44 x 0.8 / 6 x 15

= 23.45 m
Here, the closest option is 23 m.
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