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Mid-America Transportation Center

LED Traffic Signal Replacement Schedules: Facilitating Smooth Freight Flows

Final Report
click to download report


Missouri University of Science & Technology


  • Principal Investigator: Suzanna Long ( 573-341-7621)
  • Graduate Students
  • Casey Noll
  • Sean Schmidt
  • kiran rangarajan
  • Project Status
  • Start Date: 9/1/2010
  • End Date: 8/31/2011
  • Sponsors & Partners
  • Missouri Department of Transportation
  • About this Project
    Brief Project Description & Background
    Over the last two decades light-emitting diodes (LEDs) have replaced incandescent bulbs in traffic signals use because of their energy saving and much longer service life. The standard practices of maintaining and replacing incandescent lamps cannot be simply transferred and applied to LED signals. This project develops a statistically significant maintenance and replacement schedule for LED traffic signals. Data collection develops a unique process for taking readings from the driver perspective to better correlate ITE guidelines with properties of LED technology.
    Research Objective
    The goal of this study is to provide a repeatable methodology that can be used by the Missouri Department of Transportation (MoDOT) and other DOTs to evaluate the life expectancy of LEDs based on the realities of traffic intersections in Missouri and the basic science of LED components, as well as provide guidelines for cost-effective replacement schedules based on these findings. The study uses a combination of field testing and statistical analysis
    Potential Benefits
    The majority of agencies replace LED signals on a spot basis when they receive a complaint. The labor cost associated with sending a crew out to replace a single LED is very high; by calculating the expected life of an LED and knowing the probability of failure at any given point in time from the distribution function, group replacement strategies can be implemented far more effectively. This research will create operational and financial efficiencies, as well as improve safety, for transportation agencies utilizing LED traffic signal technology. The research will develop a cost-effective, less labor intensive data collection mechanism along with statistically robust maintenance and replacement schedules.
    LED technology is being widely adopted for use in sustainable traffic signal management as part of a well-connected economic system designed to address the rapid increase in freight movement. However, the useful life and luminosity characteristics have not been sufficiently studied to provide a life cycle analysis of the technology from a “green” perspective. LED traffic signals fail when their luminous intensity falls below a pre-specified threshold, posing a danger to traffic. This research details a field study of LED traffic signals in Missouri and develops a replacement schedule based on key findings. Rates of degradation were statistically analyzed using Analysis of Variance (ANOVA). Results of this research will provide a methodology for engineering managers in state departments of transportation and local communities in identifying best practices and replacement standards for LED traffic signal technology.
    Total Project Cost
    $ 110,676