The technology for this exists now. Everywhere there are bridges, the weight of the vehicles passing over the roadway could be converted to electricity. This is how truck scales are powered. New York City's RFK Bridge would be a good site because it is above Randall's Island, a city owned site where battery storage and transmission lines could be sited, and it is very near a Con Ed power plant, with a link to the grid already in place. All cars have to slow as they pass over the tolls.