I was just driving through a construcion zone, heading east at about 9:00AM so the sun angle was still pretty low. The lanes had been rerouted several times, and the old markings were ground off but this still left lighter stripes in the concrete where the paint had been. In that lighting it was very difficult to distinguish the currently-painted lanes and the old, now ground-off lane markings. As I made my way through, I found myself wondering how a self-driving car would cope.