The paper considers the justification for the application of light-emitting diode (LED) technology to urban lighting. The results suggest that LEDs are convenient for architectural lighting and deserve to be considered for use in ambient lighting. The recently developed Commission Internationale de l'Eclairage (CIE) mesopic system enabled the inclusion of mesopic effects into a comprehensive technoeconomic analysis, which dealt with efficiency, maintenance and financial aspects of the use of LEDs in street and roadway lighting. It is concluded that the average energy savings when using LED instead of high-pressure sodium (HPS) luminaires amount to 19-26% for single-sided, staggered and opposite layouts, although they are frequently negligible if mesopic effects are not included. The total costs of the LED lighting solutions, even including mesopic effects, are 1.36 to 6.44 times higher than those of the comparable HPS lighting solutions. Therefore, LEDs are questionable for street and roadway lighting.

Since practical application of the recently developed CIE mesopic system assumes the development of new measurement devices, recommendations and software for road lighting design, this paper presents a corrected photopic luminance table, which enables lighting designers to use the existing design procedures and measurement methods until all of these tasks are accomplished. It is also shown that there are numerous reasons for the practical application of the CIE mesopic system, although only photopic vision is involved in on-axis object recognition. Using the corrected photopic luminance table, an analysis is conducted regarding the potential electricity and cost savings when applying white light sources, which are more visually effective in the mesopic range.