LEUKOS
The Journal of the Illuminating Engineering Society of North America Volume 4 Number 2 October 2007
Editorial
Articles
ALEKSANTERI EKRIAS, MARJUKKA ELOHOLMA, AND LIISA HALONEN
This paper focuses on road lighting measurements and calculations. Road lighting measurements are made to study the definition of appropriate road surface luminance levels during different weather conditions. Measurements took place in five pilot locations where the effects of snow, rain, and fog on road luminances were examined. Through the measurement results, the effects of weather on road luminances are introduced and analyzed. The dimensioning and investigation of different weather conditions and their effects on visual conditions in driving offer new ways to optimize intelligent road lighting control and to make it more efficient. With an effective road lighting control system and real-time luminance measurements, electricity can be saved without adversely affecting either the safety of driving or the quality of road lighting.
MARTIN MOECK
High dynamic range images can be converted into luminance maps if the response curve of the camera is known. Previous results for a consumer grade CCD camera have shown luminance errors as a function of Munsell hue and value. New measurements with a digital SLR camera with a CMOS sensor find two problems. First, saturated hues, especially blue, blue green, and purple are still difficult to measure. Second, surfaces with low reflectance below Munsell value N4 can be significantly overestimated, especially in spherical images obtained from the photography of mirror spheres. Nevertheless, it appears that HDR imaging is a suitable tool for luminance measurement if the scene contains luminance reference values such as calibrated matte color checkers and gray cards, and if dark surfaces and saturated hues are excluded. Spherical HDR images obtained from mirror spheres capture nearly the entire environment, but resolution and decreased sensitivity for surfaces with very low reflectance are still problems.
OMER TSIMHONI, JONAS BARGMAN, AND MICHAEL J. FLANNAGAN
Current headlighting and road lighting are only partly effective in reducing the risk of driving at night. To further reduce this risk, two major sensing technologies for night vision systems have been receiving particular development interest: near infrared (NIR) systems, which actively illuminate the scene in the near infrared spectrum and capture the reflected radiation, and far infrared (FIR) systems, which generate images by passively detecting thermal emissions. To compare pedestrian detection with night vision systems, a test vehicle equipped with an NIR and an FIR system was driven at night on several roads with pedestrians standing along the route. Video clips, recorded from both systems simultaneously, were later shown in a laboratory to 16 subjects (eight younger than 30 years and eight older than 64 years). Subjects pressed a button as soon as they saw each pedestrian. Detection distances with FIR were, on average, three times greater than with NIR. For both systems, detection distances of younger subjects were about 1.7 greater than of older drivers. The effectiveness of night vision systems can be expected to depend on inherent advantages of either technology as well as the details of implementation. To the extent that the two systems used in this experiment reasonably represent the respective technologies, the results support the expected enhancement of pedestrian detection in FIR systems.
MICHAEL SIVAK, BRANDON SCHOETTLE, AND OMER TSIMHONI
The nighttime road fatality rate per distance traveled in the U.S. is about three times the daytime rate. The crashes that are most influenced by the lower ambient illuminance at night are those involving pedestrians. Here we report on the effect of different levels of illuminance provided by the different phases of the moon on nighttime fatal pedestrian crashes. The results indicate that the frequency of pedestrian fatalities on nights with a new moon is 22 percent higher than on nights with a full moon. This finding indicates that pedestrian crashes are sensitive to differences within low levels of ambient illuminance.
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