An Assessment of Energy Efficiency and Carbon Reductions from Replacing Halogen Lamps with Light Emitting Diodes in Traffic Lights — A Case Study of Gloucestershire County's Initiative

Gloucestershire County Council (GCC) in the United Kingdom has recently initiated a project to replace all of its halogen lamps in traffic lights with low energy Light Emitting Diode (LED) lamp heads across the County. In order to assess energy savings and carbon reductions from the initiative before implementation, baseline energy monitoring was carried out at 45 sample sites using a power analyzer equipped with a data logger. A regression model to predict annual energy consumption was developed with the numbers of each type of lamp head for each junction as independent variables. The model parameters were then used to estimate baseline emissions for a single trial site where LEDs have been installed and for which energy monitoring was carried out. The estimated baseline energy consumption for this site and the monitored energy consumption after the LEDs have been installed were used to estimate the actual energy savings that can be expected from GCC's initiative. Annual energy savings from this analysis were estimated to range from 64.2 to 74.1 percent (95% Confidence Intervals). The cost savings resulting from the LED initiative were found to payback the investment over a period of about six years. This paper presents a low cost approach and method by which the energy and cost savings of a large scale replacement initiative can be estimated with a single pilot replacement installation of a traffic signal. Such an exercise would be useful for local governments to carry out before making large investment decisions.