This report deals with visual task performance based approaches to mesopic photometry, with a major aim to establish appropriate mesopic spectral sensitivity functions to serve as the foundation of a system of mesopic photometry. A review of the most important visual tasks and the range of visual conditions typically encountered in the context of night-time driving is given.

The existing visual performance based systems for mesopic photometry were reviewed and tested with new independent data sources. The outcome of the analysis and testing is a recommended system for mesopic photometry based on visual performance. The report summarises the justifications for the recommended system and gives general guidelines for its use and application.

The publication is written in English, with a short summary in French and German.