> The infrastructure should be in place to detect cars approaching from the side street. Once they have the ability to detect cars, it's simple to assume everyone would be requesting a green light.
Historically, traffic control systems detected cars with sensors embedded in the road. The cars had to come to the light to be detected.
It's the most reliable method, but it requires the car to nearly come to a stop first to get to the right spot.
It's easy to imagine more complicated computer vision or radar systems detecting cars. These are orders of magnitude more complex, though. When cities install traffic infrastructure they want to leave it alone and service it as infrequently as possible. It also needs to last for decades before replacement. Modern systems that are cheap, robust, and can detect traffic from a distance throughout different conditions like rain, snow, dark, and fog reliably are a recent invention. It's going to be decades before these are widely retrofitted to long-standing infrastructure.
Historically, traffic control systems detected cars with sensors embedded in the road. The cars had to come to the light to be detected.
It's the most reliable method, but it requires the car to nearly come to a stop first to get to the right spot.
It's easy to imagine more complicated computer vision or radar systems detecting cars. These are orders of magnitude more complex, though. When cities install traffic infrastructure they want to leave it alone and service it as infrequently as possible. It also needs to last for decades before replacement. Modern systems that are cheap, robust, and can detect traffic from a distance throughout different conditions like rain, snow, dark, and fog reliably are a recent invention. It's going to be decades before these are widely retrofitted to long-standing infrastructure.