Within the research project at issue there was to be identified a method to measure the night-time visibility of road markings dynamically during wetness that correlates with the static measuring methods used at present. To measure the night-time visibility under dry conditions dynamically and according to the CEN-geometry (equivalent observation distance: 30 m) there are four different measuring instruments in action worldwide. For the dynamic measurement of the night-time visibility during rain a French team has made first researches and during wetness there is a method of a Swedish company that so far shall work on profiled marking systems only. A prototype was developed for the dynamic watering. The water was applied onto the marking by using an efficient pump and pressing it through up to 6 nozzles. It was possible to regulate the moistening width as well as the applied amount of water smoothly by using a height adjustment. The watering unit and the measuring unit (ZDR 6020 RL) were put into two different vehicles. The optimal time period between the dynamic watering and the dynamic measuring of the night-time visibility during wetness of the marking was 5-10 s. An optimal amount of water of 420 ml/m2 was determined for structured markings. For markings with a smooth surface the optimal test arrangement could not be found so far. For the dynamic watering more water has to be used than it was assumed beforehand. At a driving speed of 60 km/h and a flow of water of 3.85 l/s the use of water amounts to 1000 l in 4 min or as well in 4 km. This is why an entire dynamic measurement of the night-time visibility with dynamic watering is probably not possible. The system for the dynamic measurement of the night-time visibility of markings during wetness presented here is not entirely ready for practice yet. It is proposed to test the measuring method subsequently to this research project in a large-scale experiment. (Author/publisher)
Abstract