What lights are placed above traffic lights in Pennsylvania?

(WHTM/NEXSTAR) – On many traffic lights throughout the United States, there is a small light placed between or to the side of the traffic lights. Sometimes they are seen blinking as emergency vehicles pass.

So what is it ?

These are called priority or preemption signals. The lights are part of a system that allows the operator of a vehicle to bypass the normal operation of a traffic light.

Emergency Vehicle Preemption (EVP) systems in Maricopa County, Arizona, were first installed in the early 1980s in hopes of reducing response times. Fire trucks and other emergency vehicles are equipped with transmitters that communicate with traffic signal receiving devices.

When a transmitter is activated, the device will immediately flash traffic lights in the vehicle’s path and give priority in the direction the vehicle is traveling.

These preventive indicators allow emergency vehicles to access the scene more quickly and clear a path for the vehicle. It can also improve safety by assigning a red light to all other lights in the intersection, so that no traffic obstructs an emergency vehicle.

Many preemptive indicators are equipped with confirmation lights. This is the white light that people see when activated. The light can be flashing or steady, both having different meanings.

In Pennsylvania, for example, if the light is steady, that means the signal has been preempted and will give a green light for a signal in that direction. However, if the light is flashing, it means that the signal has been preempted to give the green light in a different direction.

Some of these systems use a line-of-sight system, which allows a narrow, forward-directed signal toward traffic lights in front of the vehicle to gain priority. Others use GPS and some use a radio signal to gain the same right of way.

South Georgia Medical Center, which announced in June 2023 that it would equip all of its ambulances with GPS-ready EVP devices to help responders stop cross traffic when rushing to an emergency.

“This innovative technology makes ambulance responses safer for everyone,” Michael Colman, chief of emergency medical services at South Georgia Medical Center, said in a statement.

The hospital group found that the devices reduced response time by an average of 11 seconds per traffic light.