All cars produce excess power while operating. How about putting a tesla type coil on the roof and have a receptor cable over freeways? In this way the cars excess power could be directly transferred to adjacent communities. I honestly think the return would be phenomenal.
Update: On further thought, with the popularity of electric vehicles how about a system that could zap a quick power charge as they drove past. In this way modern gas guzzlers could contribute something back to the more environmentally friendly cars.