You know those little spinning reflective pinwheel things by construction sites that act as a traffic-powered beacon? What if we took the same idea and attached one to every street light at the center of the interstate with a little generator inside. Every light is then powered by the wind from the cars driving past. They can store energy, too, and use it very slowly, leaving the lights fairly dim when there is hardly any traffic, and allowing them to get increasingly brighter as more cars approach. During the day, the generated power can be redirected to the city’s main grid.