Red Light Not Turning Green? You May Be Able To Help The Sensor Detect Your Car

Modern traffic light technology isn't just a simple sequence of red, yellow, and green. It's a complex detection system designed to manage traffic flow based on real-time demand. The very first "smart" traffic lights used pressure plates, but modern systems rely on infrared sensors, cameras, or inductive loops to detect a vehicle. When cars reach the line, the approach system sends a signal that triggers the green-light cycle.

While this technology is typically reliable, there may be rare circumstances where a traffic light is malfunctioning or your vehicle is too small for the sensors to detect it. This is the reason why motorcycles can get stuck at traffic lights, for example. However, it is more likely that your vehicle is not positioned correctly to allow the sensors to detect it.

The best way to help the sensor detect your car is to position the vehicle directly over the loop's most sensitive area. These are usually the embedded cut lines in the pavement, which you'll want to make sure not to roll past too much. If you are riding a motorcycle, stopping directly over the cut line can improve detection, and some riders have even reported trying to put the kickstand down to help the system work.

Knowing how traffic lights work and how they detect your car can help you understand how to position your vehicle for the best chance of being detected. Most modern systems use the aforementioned inductive loops buried beneath the pavement. These are designed to detect changes in their electromagnetic field caused by nearby vehicles. When a sufficient amount of metal is positioned above the loop, the system recognizes that a car is present.

Some traffic lights also use video-based AI cameras mounted on top of the intersection. These analyze traffic to detect approaching vehicles. Others use doppler radars to measure distance and speed, so they can dynamically respond to approaching vehicles. 

Infrared sensors can also be used. When you approach those, you won't be detected if you are behind any obstacles because IR is directional. The most advanced traffic lights use connected-vehicle (vehicle-to-infrastructure) systems which are able to "talk" to a vehicle, especially emergency services and public transportation. One day, these could also be used for autonomous cars as well.

Even though better positioning will most often help turn the light green, there are situations where the inductive loop is damaged or the camera isn't able to see you approaching. If this happens, there are a few things you can do depending on the type of traffic light. For one, make sure you wait plenty of time, as some lights have a back-up timer installed that makes the light change even if one of its more complex systems fail.

According to the National Association of City Transportation Officials, red lights in cities typically last between 60 to 90 seconds before turning green. However, the most infuriating red light in the U.S. used to last more than five minutes, so they can certainly make you wait. If the light won't turn green even after you've waited a few minutes, try waiting until another vehicle comes to see if that one triggers it. You can also observe whether other lights in the intersection are functioning properly.

If you are truly stuck, some jurisdictions do allow you to treat a malfunctioning traffic light as a stop sign, meaning you have to come to a complete stop and only continue if it's safe and your turn.  However, be sure to check what the law is for this situation in your region. Regardless, always pay close attention to all other drivers on the road. It's also a good idea to contact your local traffic authority so they can fix the problem.