Extended Runtime at Signalized Intersection Using Backup Power after the Loss of Utility Power

Lessons learned after hurricanes revealed that although most traffic signal infrastructure withstood the impacts of the storms, signalized intersections were not operational due to lack of utility power. It is very dangerous without signal operations at major signalized intersections. Because of the problems associated with the use of generators to run intersections, such as purchase and replacement costs, storage issues, and costs of placement in the field after a storm, the subject needs further research for viable solutions. Current traffic cabinets employ a standard uninterrupted power supply (UPS) system, which is powered by lead acid batteries, an outdated technology that provides power for only up to eight hours of operation. Sponsored by the Florida Department of Transportation (FDOT), researchers coordinated with staff at FDOT Traffic Engineering Research Lab (TERL) in Tallahassee to evaluate backup power systems to support the extension of the runtime at a signalized intersection after the loss of utility power due to hurricanes.

A liquid propane generator was tested that successfully provided constant power without issues; the only limitation was the availability of fuel. A lithium battery system also was tested, which powered the test signalized intersection for 20 hours, more than enough to cover nighttime operations. A system that included a battery + solar backup was tested successfully and provided power for several days without issues. This system uses smaller battery capacity but requires sunny weather to charge the battery and power the intersection during daytime; this is not usually an issue after hurricanes, especially if adequate solar energy generation is provided to charge the battery during available daytime hours. The result of the testing provides valuable options for transportation agencies to consider implantation to extended runtime at signalized intersection using backup power after the loss of utility power due to hurricanes to improve the intersection safety.