Field evaluation of selected light sources for roadway lighting

The development of new lighting sources, such as light emitting diode （LED）, induction, and plasma, presented more possible cost effective ways for roadway lighting. A study was therefore conducted for the Indiana Department of Transportation （INDOT} to evaluate the performance and effectiveness of some selected new lighting devices in roadway lighting. This paper describes the field evaluation process and presents the evaluation results. A number of LEDs, plasma and induction luminaires from various manufacturers were selected to replace the existing high pressure sodium （HPS） lamps in conventional and high mast lightings, llluminance values were measured over a period of 12 months on the existing and new light sources. Light performance metrics, including illuminance level and uniformity ratios, were calculated to make quantitative comparisons of the HPS and new types of light devices. Based on the evaluation in terms of lighting performance and life cycle costs, it was concluded that LED luminaires should be utilized in roadway lighting in place of HPS luminaires. The results of this study will be useful to state highway and city street agencies in making decisions on their lighting policies and developing technical specifications for use of the new lighting technologies in roadway and street lightings. The study provides a basis for manufacturers to improve their luminaire design and integration to better fit the needs of roadway and street lightings.

An electrophosphorescent organic light emitting concentrator

We demonstrate threefold directional light concentration from an organic light-emitting diode luminaire for use in spot lighting and other applications where high intensity illumination is required.The concentrating luminaire comprises four triangular,large-area green electrophosphorescent organic light emitting diodes(PHOLEDs)deposited on plastic substrates and assembled into a pyramidal structure with an open base that serves as the light exit aperture.The PHOLED surfaces are highly reflective to direct the emission from the devices to the aperture independent of the original emission position within the pyramid.The far-field intensity profile of the concentrator has a‘batwing’distribution that meets the requirements for general lighting for uniform illumination of planar surfaces.

Cost effectiveness of new roadway lighting systems

Appropriate and adequate lighting at select locations on roadways is essential for roadway safety. As the lighting technologies advance, many Wpes of new lighting devices have been developed for roadway lightings. The most promising new lighting technologies for roadway lighting include light emitting diode, induction, plasma, and metal halide lighting systems. A study was conducted to compare the new systems with the conventional high pressure sodium systems that are currently used on the Indiana roadway systems. In this study, the engineering issues, were analyzed such as illuminance, color rendering, power usage, cost effectiveness, and approval procedures for new roadway lighting systems. This paper, however, presents only the study findings related to cost effectiveness of the evaluated roadway lighting systems. Illustrated in this paper are the main features of the roadway lighting systems under evaluations, installations of the new lighting systems, measurements of power consumptions, and life cycle cost analyses of the lighting systems. Through this study, experience and knowledge have been obtained on the installations, power measurements, and cost effectiveness of the new types of the roadway lighting devices. The actual power values of various luminaires were obtained by measuring the electric current with a multi-meter. It was found that the differences between the rated and measured power values could be significant. The results of the life cycle cost analysis indicate that the lower life cycle costs of some of the alternative lighting devices are attributed to their relatively lower electricity usages and longer lamp/emitter replacement cycles.