The city will evaluate the pilot in the fall, and may try the devices in other locations.
The workers replaced aluminum poles with new, safer fiberglass poles that do not conduct electricity.
There are about 3,000 traffic signals in Philadelphia, and some are more susceptible to cold than others.
The Traffic Signal Improvement Project will be conducted in the northeast quadrant of center city, which runs from Callowhill Street south to Market, and from Broad Street east to Second.
Access to the Schuylkill River Trail has been blocked at Race Street, leaving residents to fear keeping the gate closed is unsafe.
“We actually are using wireless technology to determine the speed of the car,” says city chief traffic and street lighting engineer Richard Montanez. “And then, based on that, we trigger the red light.”