I36 & I25 in Denver has a new switchable transponder for the HOV/toll lane. I put one on the windshield of my S. I just got my first statement and their system did not see the transponder and billed me via license plate (even though I was HOV). I called and they said that Tesla windshields have some sort of coating that prevents them from seeing the signal from the transponder, so I have to call and get a refund each month until they 'figure it out'. At first they blamed it on it being an electric car, then they finally agreed that had nothing to do with it and it was a windshield issue. I can't imagine what is so special about Tesla windshield that other high-end cars don't do.