The objective of this research is to build lifetime curves for red, yellow, and green LED circular traffic signals through 20,000-hr. Light Emitting Diode ( LED) circular traffic signal lifetime management system. Further investigations on the effect of ambient illumination and other designs of self-luminous traffic signs are in progress. Based on the four LED traffic signs evaluated in this study, we suggest LED lightbox as the prior choice. Only LED lightbox has significantly better visual comfort than external LED lighting in the brighter environment. LED lightbox has significantly better preference score than LED backlight under darker ambient lighting. Among the three self-luminous signs, regional LED backlight is most susceptible to the ambient illumination.

The results show that self-luminous traffic signs provide superior legibility, visual comfort and user preference than the non-self-luminous one. The ambient illuminance is 2.8 and 6.0 lux in two rounds. The illuminance of external LED lighting is 400 lux on the traffic sign. The luminance of three self-luminous signs is 216 cd/m2.

The signage dimension is one-sixth of the real freeway traffic signs, and the observation distance is 25 m.

The four signs are hanged side-by-side and evaluated by observers through questionnaires. To investigate the legibility and visual comfort of LED traffic signs, an ergonomic experiment is performed on four custom-designed LED traffic signs, including three self-luminous ones as LED lightbox, LED backlight and regional LED backlight, and one non-self-luminous sign with external LED lighting. Visual ergonomic evaluations on four different designs of LED traffic signsĬhen, Yi-Chun Huang, Ting-Yuan Lee, Tsung-Xian Sun, Ching-Cherng The survey results confirm an overall positive impression on LED performances in traffic lights. The results of the measured levels of illumination show that deposition of dirt considerably affects its values. Examination of the LED Source in Traffic Lights and the Effect of Airborne Dirt on its Performanceĭirectory of Open Access Journals (Sweden)įull Text Available The performed evaluation consisted of two phases: measurement of the illumination levels of (new LED system and carrying out the public opinion poll on the subjective visual performance of LED in traffic lights.

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