1. This method wouldn't work in heavy traffic. 2. That "nearly constant 10mph breeze" is improving fuel efficiency for the cars behind you through reduced wind resistance. 3. A similar idea for generating power from traffic is through the use of speed bumps as power generators. But that doesn't work either. Here's an interesting article from wired: http://www.wired.com/science/discoveries/news/2001/06/44518