system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the current self-driving cars know to do the more 'complicated' things like starting up at a green light or yielding at a 2 way stop.

Perhaps they don't and they can only go on highways now?
gpt
Those things aren't much more complicated than staying inside the lane by not drifting over the white/yellow lines. 

When the camera detects a stop sign it should also identify the start of the intersection and hold the car stationary there for a second or so before decided to advance or wait on another vehicle. Car on the road to the right? Wait until it has passed. 

When a street light is seen hanging over an intersection advance through only if the green light is active. If it's not pull to halt before the start of the intersection and wait until it is. 

These are fairly simple ideas to program, the real difficulty is writing the software that lets you identify stop signs, traffic lights and the like from your camera feeds.