Why don't they exist? Instead we have technology that relies on sensors and timers. Traffic engineers program these giant metal boxes based on data from a small timeframe of observation and data collection from cable sensors.

Then you have the occasional survey from the city asking about traffic signals. And then you have the reason for traffic signals not being in sync is intentional to prevent shoplifters from getting away.

Traffic signals today are archaic and stupid. You may as well put four way stop signs everywhere because how we use traffic signals today isn't smart.

Imagine a traffic signal prioritizing the flow of traffic. And when it sees a clog it makes adjustments to maximize the flow. No more going through a loop where it's probable that no car is moving.

Lights are changed only for the sake of flow. And flow isn't stopping one car for 24.

If a car needs to cross an intersection of a priority road why not give them a blinking red light signifying you can go only if it's safe? Why should the traffic signal go red on a priority road when flow isn't a concern and it's not high traffic?

At times the flow of a four way stop sign interchange is better than one with a traffic signal.

I could see Tesla's Vision helping solve this.