17-229-204 Me. Code R. § 03
The principal design for installations of new highway lighting systems will be average intensity, uniformity of illumination, and economics. Average intensity of illumination expressed in horizontal footcandles is a measure of the total illumination on the roadway surface. Uniformity will be average to minimum intensity ratio for the total illumination distributed on the road surface.
The actual spacing of luminaires will be based on the average intensity of illumination needed, the light that can be utilized from the luminaire, and the area to be covered by the luminaire. The following formula will be used:
Lamp lumen at Coefficient of Luminaire
Replacement x Utilization x Maintenance
Spacing Time Factor
Between =
Luminaires Average Intensity Total Area
of lumination x Covered
After the luminaire spacing has been calculated, the uniform ratio shall be checked using the following formula.
Average Illumination
Uniformity Ratio =
Minimum Illumination
The uniformity ratio should generally not exceed 6:1.
17-229 C.M.R. ch. 204, § 03