Luminous Efficiencies of Common Light Sources of Road Lighting in Mesopic Lighting Level

It is inappropriate to define the luminous efficiencies of light sources based on the photopic luminous efficiency function V(λ) in road lighting application,because road lighting is under mesopic level.In order to define the luminous efficiencies in mesopic level of common light sources of road lighting,and provide advices for designers to choose lighting sources properly,and for road lighting design to save energy,this paper studies light characteristics of two common light sources of road lighting,high pressure sodium lamp and metal halide lamp(dysprosium lamp),calculates the luminous efficiencies of these two light sources under mesopic level,analyzes luminous efficiencies′ changing rules with the change of background lighting level of these two light sources under mesopic level.The conclusion is that light level of road lighting should be considered when choosing light sources.