Road Lighting Regulation in Relation to Vertical Illuminance and Vehicle Stopping Distance

The paper deals with a model situation of a traffic area illuminated by a combination of vehicle low beam headlamps and luminaires of road lighting. In the model situation, the distribution of vertical illuminance in front of the vehicle located directly below the luminaire was evaluated. When the vehicle is positioned below the luminaire, the shortest distances in front of the vehicle occur, in which conditions are sufficient for obstacle detection. The model boundary conditions chosen represented the least favorable situation in terms of visibility in the traffic area. The aim of the study was to evaluate the visibility in the area in front of the vehicle during the operation of the luminaires of road lighting with the regulation of luminous flux output. The main motivation for the operation of luminaires of road lighting is to save electrical energy and are justified by the decrease in traffic volume during late night hours. However, is it appropriate to implement dimming of luminaires without taking into account the visibility of obstacles in the traffic area [1], [2] depending on the stopping distance affected by the maximum permissible vehicle speed?