That seems like one of the easiest problems, much easier than actually navigating a well-organized road system like in the USA. If the car can follow a lane the

That seems like one of the easiest problems, much easier than actually navigating a well-organized road system like in the USA. If the car can follow a lane then it can certainly know when it detects no discernible lane. If the car can avoid obstacles like a pedestrian or a car crossing its lane, then it can certainly know when there is a chaotic mess of obstacles crossing its lane.