Q: At an intersection with a red light camera, what is the period of time required by the camera to be considered a complete stop before making a right turn on a red light?
A: There’s a story behind this question, isn’t there? Did anyone else read that question and think to themselves, “Someone just got a ticket.” That’s way too specific of a question to be just a curiosity.
A red light camera is, at its core, sensors, cameras and a computer. The sensors, installed in the pavement, measure the movement of cars through the intersection. When the traffic signal is green the computer ignores the messages from the sensors. When the light is red, the computer listens to the messages from the sensors. If the sensor says, “hey computer, this car is still moving,” the computer tells the camera to take a couple pictures of the car. An officer then reviews the data to confirm a violation has occurred. The people who design these systems might tell you it’s more involved than that, but you didn’t ask an engineer.
I suppose the technical answer to your question is that the period of time required is whatever the designer or programmer sets it at. However, the real determining factor is the law. We know that a red traffic signal means stop. From what I’ve observed, not everyone agrees on the definition of stop, so let’s check the law. The Revised Code of Washington defines stop as “complete cessation of movement.” There’s no set amount of time you have to stop, but if you’re still rolling (even a tiny bit) you haven’t complied with the law. Based on that, a red light camera would need to be programed so that if you come to a complete stop, however brief (in the scenario of a right turn on red), it would recognize it as a stop.
Side note: If you’re making a right turn on a red light, stopping for a fraction of a second might comply with the stop requirement of the law, but is not enough time to make sure it’s safe to turn. Along with checking for cars, you also need to look for pedestrians coming the other direction. The most dominant pre-crash event of both pedestrian and cyclist collisions involve a vehicle turning or merging. Right turn on red fatalities are rare, but over half of them are pedestrians and cyclists.
Several polls, including one by the Insurance Institute for Highway Safety, have found that most drivers are in favor of red light cameras, but they are not universally loved. Some people claim that they violate the constitution (not true), they’re an invasion of privacy (not true – the law prohibits photographing the faces of vehicle occupants), and the yellow lights are shorter at intersections with cameras (also not true – the law prohibits shortening the yellow light after installing cameras). Really, the criticisms of red light cameras are mostly just us unwilling to admitting that we don’t like getting caught.
Even if you don’t love them, there’s plenty of evidence showing that they work. I could exhaust you with the many studies that find reductions in fatalities, injuries and violations when red light cameras are installed. Instead, I’ll just give you one: Red light cameras reduce fatal red light running crashes by 21 percent. We often talk about human behaviors and traffic crashes, but how we design our transportation infrastructure has a big impact on how we drive. Red light cameras are one of the available tools to build a safer driving (and walking and biking) environment.