Originally Posted by
ItsJustMe
I think what you're describing is a stoplight with sensors. Almost all stoplights are like that these days. They could be programmed to switch to flashing red when someone was at the side road, and that's equivalent to a 4 way stop, where people take turns.
Except that the sensors are at the intersection, so you have to stop before the light can go to green. Unless you live in a city like Eugene, OR, where very few of the sensors are tuned to detect bikes, even the left turn lane sensors. The city staff have taken the position that if they tune them for bikes they will sometimes detect a motor vehicle in an adjacent lane, which could cause oncoming traffic to wait for a left turn arrow that no one is there for. Far better to have cyclists wait for a car going their way in order to get a legal way out of the intersection.