Here's the view of the Autobahn. In the top photograph, light from outside is transmitted through the windscreen. It hits the dashboard and is reflected upwards. The reflected light hits the windscreen. There is a partial reflection in my direction. The bottom photograph with a polarising filter shows no reflection, so that light reflected back from the windscreen must be polarised. The angle of reflection must have been above the Brewster angle. I think this is 57 degrees for glass. I thought it looked 45 degrees just sat in the car but perhaps I didn't look closely enough. For the record, I was in the passenger seat! I was a UK registered car...
