Abstract
Power interruptions brownouts and blackouts can cause traffic signals to flash or to go dark. Traffic signals with light-emitting diode (LED) lamps consume less power and can operate on uninterruptible power supplies (UPSs) or battery backups. UPSs function as a separate source to maintain a continuous supply of electric power to connected equipment whenever utility power is not available. This article contains details of the laboratorytests of UPSs, applications of UPSs in Illinois, and the benefits that have been realized.