The main function of traffic lighting is to make the road and the road area safe for people. In order to reduce energy use and costs for traffic lighting it is imperative to have as energy-efficient lighting as possible while still maintaining the requirements for road lighting. The objectives of this project are: (I) to provide basic data for various steps leading to the energy efficiency of road and street lighting network. (II) to examine how the use of dimming and various light sources affect visibility as experienced by people. The project used a relatively new method for measuring luminance based on digital photography. This new approach made it possible to compare the luminance of 18 different measurements where the lights had different power and source. Specifically, it included five test sites with ceramic metal halide (between 70—200 W), nine measurements of high-pressure sodium (35—250 W), two measurements of compact fluorescent lamps (42—100 W) and one measure each of the OLED (100 W), and LED (100 W). This study shows that there is a potential to reduce the energy consumption of several of the existing road lightings by reducing power and still meet the requirements based on traffic safety, because the measured luminance and the illuminance show that some of the values fall between the recommended classes. There is potential to save energy by adjusting the lighting after weather conditions and this could be exploited in a much higher level than it is today, especially in the northern part of Sweden. On roads with large variation in vehicle intensity there is high potential to reduce the lighting effect to lower luminance classes during periods when traffic flows are low, provided that individual assessment is made on a case by case basis. This study highlights four different types of dimming schedules based on different conditions in which the savings in kWh/year are between 19—50 per cent. By applying different types of dimming schedules road lighting systems can be tailored to reach a very high degree of energy efficiency. In the future there are also opportunities to introduce synchronized reductions in road lighting and speed limits (so-called variable speed limits) to save energy but still maintain road safety. Results from the web survey based on photographs from roads with various lighting show that most people thought that the visibility of a dark-dressed person was best in the maximum effect level for each light source (high pressure sodium and ceramic metal halide), whereas responses were not decisive regarding the best visibility between light sources. However, the survey shows that more people (from 62.4—71.6%) choose ceramic metal halide lighting instead of high-pressure sodium in order to feel most comfortable if they would be driving. When the results were compared with another publication the power demand per km road was higher for most types of lighting we examined on 50 km/h roads in this study (they also have low pole height). Our results also show that a road with 150 W high pressure sodium lighting and power demand of 4.3 kW/km met the same MEW-class as a road with 100 W ceramic metal halide lighting. The difference is that the 150 W road had a 5 m wider spacing between the light poles. In this study, we did not detect any significant differences between high-pressure sodium and ceramic metal halide on average luminance or illuminance levels. However, measurements of uniformity of luminance and illuminance of ceramic metal halide lamps were sometimes at higher levels compared to high pressure sodium lamps. (Author/publisher) This report may be accessed by Internet users at http://www.vti.se/EPiBrowser/Publikationer%20-%20English/R722Eng.pdf
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