The correct answer is C. 20 lux.
The Indian Road Congress (IRC) is a professional body that provides technical guidance on road engineering and construction in India. The IRC has published a number of guidelines and recommendations for road lighting, including the IRC: SP: 41-2012, “Guidelines for Road Lighting Design.”
The IRC: SP: 41-2012 recommends that the average level of illumination on important roads carrying fast traffic should be 20 lux. This level of illumination is necessary to ensure that drivers have adequate visibility to safely navigate the road.
The other options are incorrect. Option A, 10 lux, is too low a level of illumination. Option B, 15 lux, is a common level of illumination for residential streets. Option D, 30 lux, is a common level of illumination for highways.
Here is a brief explanation of each option:
- Option A, 10 lux, is too low a level of illumination. This level of illumination is not sufficient to ensure that drivers have adequate visibility to safely navigate the road.
- Option B, 15 lux, is a common level of illumination for residential streets. This level of illumination is sufficient to ensure that drivers have adequate visibility to safely navigate residential streets. However, it is not sufficient to ensure that drivers have adequate visibility to safely navigate important roads carrying fast traffic.
- Option C, 20 lux, is the recommended level of illumination for important roads carrying fast traffic. This level of illumination is necessary to ensure that drivers have adequate visibility to safely navigate the road.
- Option D, 30 lux, is a common level of illumination for highways. This level of illumination is more than is necessary to ensure that drivers have adequate visibility to safely navigate important roads carrying fast traffic.