How well do sensors and vision systems handle winter conditions like snow and lack of lane markers?
The harder part is driving like a human and detecting that a path has been made in the middle of two lanes in heavy snow and not obeying the lines at all.
It's not a matter of "finding" lane markers. There are no lane markers visible after it snows.
We ourselves identify and confirm other urban waymarks via captcha which feeds the nav data -- bridges, signs, hills, hydrants, chimneys, lights. There is mass live verification from android auto in vehicles. There are many yearly layers of street view images and scans.
I don't think we'll see a system that can handle that in my lifetime.