Traffic lights, like our smartphones, are being upgraded with newer and newer technology to help getting from A to B safer and faster. Most urban cities now have new sensors and cameras on their lights, but we might be asking ourselves, “How do they work?”, “What are they doing to help me get to where I want to go, faster?”, “Can I flash my high-beams to change a red light to green?”

To help answer these questions, we contacted Harvey Turner, Traffic Signal Systems Analyst with the City of Regina, to learn about the three types of sensors you can find in and around the city.

 

Video Camera Sensors

Video camera sensors are the most commonly used in the city and look like a small metal tube perched just above traffic signals. These cameras face on-coming traffic and watch for changes between its “learned” background image (what the intersection looks like when it’s empty) and the live image. If a car pulls up to a detection zone (generally just behind the stop line), the traffic control computer notes the change in images and responds by changing the signal cycle appropriately. This might mean adding an advanced green, giving a waiting car the green light, or skipping a cycle for an empty intersection.

The City of Regina is testing a new type of sensor that uses infra-red images to detect changes in temperature instead of a video image, but the idea is still the same.

 

Microwave Motion Detector

These sensors are small rectangular boxes often found just above or to the left of a lane. These sensors work just like the motion detectors of a home security sensor to pick up the movement of a vehicle in the lane. This helps the traffic control computer determine whether to add an advanced green to a cycle, and for how long to display it for. Advanced greens have a minimum and maximum time limit. Thus, if the microwave motion detector picks up several vehicles passing through an advanced green, it will extend the length of it up to a maximum length of time.

 

Emergency Vehicle Infra-red Receiver

This is the sensor some people think they can trick into giving them the green light. The Infra-red Receiver looks like a small black can with a small tube extending out of it and is mounted along the same bar as the traffic lights. This receiver detects Infra-red signals sent by a transmitter mounted in emergency vehicles which tell the traffic control computer to switch a light from red to green in order to provide a clear path for emergency vehicles. They cannot be controlled by simply flashing one’s high-beams in the hopes of getting a green light.

 

Thanks to Harvey Turner for the information and shedding some light (pun intended) on the subject!