Traffic signal control cabinets usually employ a standard uninterrupted power supply system, which is powered by lead acid batteries, a technology that provides power for only up to eight hours of operation. Recent hurricanes in Florida revealed that although most traffic signal infrastructure can withstand the violent impacts of these storms, signalized intersections were ultimately rendered inoperable due to lack of utility power. This project investigated the applicability of backup power systems to provide extended backup power to traffic signals in the event of power loss during hurricanes. 

Three different electrical power backup systems were installed and tested at a test intersection located at the FDOT Traffic Engineering Research Lab (TERL) in Tallahassee, FL.

1. A liquid propane generator, usually not impacted by weather conditions was tested and successfully provided constant power without issues; the only limitation being the availability of fuel.
2. A lithium battery system that does not need refuel and requires less maintenance was also tested, which powered the test signalized intersection for 20 hours, which was sufficient to cover nighttime operations.
3. A system that included a battery and solar backup was tested successfully and provided power for several days without issues. 

SYSTEM COSTS

1. The propane generator used in this project had the power capacity of 8 kW and output voltage of 120 VAC. The initial purchase cost was $5,333 and considering the installation and fuel costs, daily cost of operating the propane generator was estimated as $8,669 based on 22 gallons of liquid propane generator use. The cost did not include fuel tank protection such as poles, concrete barrier, or other protective measures. The project showed that 45 gallons of propane fuel supported the tested traffic signal system for 51 hours under full operating conditions.
2. The battery used for testing was lithium-ion with 10.4 kWh battery capacity. The cost of battery was reported as $1,040 per kWh. When the installation and other required equipment costs were considered, the cost of battery powered generator was reported as $16,000.
3. The solar panel used in the project was 223 square feet with 3.2 kW power. The cost of the solar panel was $3.37 per Watt. The cost of the battery and solar powered generator was reported as $17,000 from the selected vendor.