Light-emitting diode (LED) traffic signal and uninterruptible power supply (UPS) usage: a nationwide survey

A national survey was conducted to gather information regarding the use of light-emitting diode (LED) traffic lights and uninterruptible power supply (UPS) systems in traffic signal controller cabinets. A survey was mailed out to the individual districts within Illinois DOT, all 49 other state DOTs, and to 79 of the largest cities in the US to find out the degree of utilization and satisfaction about LED traffic signals and UPS systems. At the State DOT level, there was a significant usage of LED lights in traffic signals. The most commonly used brands were Gelcore and Dialight. These accounted for approximately 95% of all LEDs in use at the state level. These results are also echoed in that both Dialight and Gelcore scored over 3.5 (out of 4.0) on the opinion-based degree of satisfaction ratings. At the city level, Dialight and Gelcore were also the most popular brands, and accounted for 91% of all LEDs in use. Dialight scored a near perfect rating of 3.923 and Gelcore also did very well with a satisfaction rating of 3.333. Finally, at the IDOT district level, Dialight was the most commonly used LED (accounting for about 95% of all LEDs in use), and also scored the highest satisfaction rating, at 3.833. The UPS Usage indicates that at the State DOT level, there was some usage of UPS systems, but it had not achieved widespread acceptance. From the 7 states that indicated using UPS systems, 7 different brands of UPS systems were identified. At the city level, there was even less acceptance of UPS systems at the time of this survey, with only 4 cities reported using 6 different brands. All 6 of these brands were in use by only a single city, so no average ratings were available.