Glare, luminance, and illuminance measurements of road lighting using vehicle mounted CCD cameras

The assessment of well-designed road-lighting systems is necessary since their performance can be critically reduced by incorrect installation. During the operational life of a system, it is also necessary to assess the effects of deterioration in the luminaire fittings, changes in road surface or surroundings and changing user needs. An automated vehicle-mounted system constitutes the most practical technical solution to carry out this task. Previous research produced image acquisition and analysis systems for measuring luminance and uniformity levels of road lighting (Glenn 2000). Mis paper builds on this work anal describes the methods employed to assess the combined parameters of luminance, illuminance and glare. A description of the system components is given, including the CCD digital video cameras, which are mounted on the test vehicle. 711e cameras are pre-calibrated to estimate relationships between gray value of light images and lighting parameters (luminance and illuminance). Appropriate infra-red and neutral density filters are employed to control the wavelength and limit the light entering into the cameras. Differential GPS, 3D orientation sensors, and image,flow analysis, are employed to accurately estimate the position of the vehicle. Automated image analysis methods are further developed to speed up the position and image analysis process. Multidirectional measurements of light output are achieved using multiple journeys and multiple cameras on the same road-segment, which provide data on different observation lines. Interpolation techniques are employed to estimate the complete profile and produce isolux contours. Results produced so far indicate that lighting parameters can be measured accurately, provided that accurate 3D information of luminaires and road layout is available. Further work is reducing the dependency of the system on this a-priori data and using only readily available utility data.