New Model for Mesopic Photometry and its Application to Road Lighting

Abstract

There are definite needs for a practical system of mesopic photometry to be used in lighting dimensioning and measurement of road and other outdoor lighting applications. A research consortium, MOVE, combined the resources of several European research institutes to establish a basis for performance based mesopic photometry. A practical system of mesopic photometry is introduced as a result of the MOVE work. In this paper the MOVE model was applied to road lighting conditions and the model predictions were compared to luminances based on photopic photometry. The calculations using the MOVE model show that the adoption of mesopic dimensioning would affect road lighting practice over the whole luminance region of the present recommendations.

Both the model of MOVE and the recently proposed X-model by Rea and others, are linear descriptions of mesopic luminous efficiency between the scotopic V'(Λ) and the photopic V(Λ) functions. The two models are not, however, similar in their prediction of mesopic luminances. The paper compares the two models and discusses their differences.

The paper concludes by outlining the implications of mesopic dimensioning in road lighting and the future actions on the way towards mesopic lighting practice.

Keywords:

• mesopic
• photometry
• road lighting
• visual performance
• spectral luminous efficiency