United States Department of Transportation
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Edition:Final report 11/2010 - 11/2015
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Abstract:This research originated from the opportunity to develop a methodology to assess when LED (Light Emitting Diode) traffic signal modules begin to fail to meet the Institute of Transportation Engineers (ITE) performance specification for luminous intensity for motorists. The ultimate goal of this research project is to provide the Louisiana Department of Transportation and Development (DOTD) with a replacement schedule for LED signal modules. To this end, the objective of this research is to develop lifetime curves of these modules and to establish the life-span of signal modules. These curves will depict how these modules’ luminous intensity degrades until reaching the end of their useful life. The research methodology and findings will allow other researchers in different climatic regions to test their own modules. In this research, the operating time of LED signal modules is equal to 20,000 hours of operation. The research methodology is comprised of three data sets of measurements of the luminous intensity of the signal modules. The first data set was collected by an independent lab with multiple data points per module. This lab data set was measured sequentially at a fixed 2,000-hour time interval for the first 10,000 hours of operation, and then once again at 20,000 hours. The other two data sets were collected by DOTD employees at the Traffic Services yard using two distinct devices with one data point per module. These in-house data sets will be measured sequentially at a fixed 500-hour time interval for the duration of this research project. The results of this study indicate that a five-year replacement schedule of LED modules appears to be too soon. It is unknown at this point what the exact lifetime curve of these specific LED modules is.
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