Phase II of this study focused on developing a draft specification for LED luminaires to be used by IDOT and a life-cycle cost analysis (LCCA) tool for solid state lighting technologies. The team also researched the latest developments related to dirt depreciation factors for LED luminaires and other general developments on solid state lighting. A final draft specification was developed that included best practices from states and cities that already had their own specification, as well as feedback from several state DOTs staff, a few experts in roadway lighting, and six LED luminaire manufacturers. This process is recommended for the development of future specifications. A spreadsheet to conduct LCCA based on net present value was also developed. The spreadsheet contains unit costs of typical items used in roadway lighting projects, and it is completely customizable by the user. The life-cycle cost of HPS, LED, plasma, and induction lighting designs can be compared side by side in the output table. There are significant trade-offs between larger initial investments for LED and lower maintenance/light consumption costs over the life of the project. Presently, LED lighting does not offer significant cost advantages over other technologies used in highway lighting in most of the four scenarios analysed. However, assuming re-lamping and re-ballasting cycles of 4 years for HPS, and a cost of $845 per LED luminaire (half of current cost reported by IDOT), HPS and LED produced the most economical lighting solutions with the exception of the conventional interchange project in which LED was 8.3% more expensive than HPS. Ongoing dirt depreciation research and trends in the lighting industry, such as adaptive lighting, should be monitored to take advantage of developments and to ensure that the most qualified products are specified and purchased. In addition to LCCA, other factors may also be considered in deciding which type of luminaires to use. (Author/publisher)
Abstract