Traffic Signals

Traffic Signals


The City has 35 traffic signals and 36 warning flashers.

  • Three signals owned by the State of Idaho are maintained by the City under a maintenance agreement between the City and State.
  • Six signals in the downtown area have preset timing intervals and do not change with the traffic volume.
  • Remaining signals are traffic actuated from 6' x 6' wire loops embedded in the pavement and are known as traffic detection loops. These loops detect vehicles as they approach the traffic signal and send information to a control cabinet located on a corner near the intersection. The traffic control cabinet then assigns most of the available green time to the heaviest traffic movements. Traffic signals on 21st Street, Thain Grade, and Thain Road are in a coordinated system; the goal of which is to safely move the greatest number of vehicles through the system with the fewest number of stops.

Waiting Time

In the traffic control box, priority is programmed for the main arterial, or the street with the majority of traffic. This means that vehicles traveling on side streets entering a street like 21st have to wait longer for a signal to change.

Emergency Vehicles

Some signalized intersections also have emergency vehicle preemption, meaning the emergency vehicle will have a preprogrammed green light priority. The purpose is to allow the emergency vehicle to pass through the intersection as quickly and as safely as possible.

Light-Emitting Diode


Cities across Idaho are installing energy-saving LED (light-emitting diode) traffic signal lights. LED traffic signals are long-lasting, energy-efficient lights that can be easily installed in the existing signal head structure. 

While producing highly visible light, LEDs consume 80 to 90 percent less energy than incandescent signals. LED traffic and pedestrian signals generally use 9 - 25 watts, compared to the 75 - 150 watts used by an incandescent signal. Because traffic signals operate 24 hours a day, 365 days a year, the opportunity for savings is huge. 

In addition to saving energy, LED signals also can reduce re-lamping cycles of maintenance. This is because LEDs generally last five to seven years, compared to just one year for an incandescent light signal. The City has installed 367 LED energy saving red lamps in traffic signals. The green and "Don't Walk" indications will be replaced as funding allows. To date, 49 amber, 283 green, and 218 "Don't Walk" have been replaced