Increasing powertrain efficiency is just one area in which vehicles' environmental impact can be lessened. A significant portion of the total energy used to operate the vehicle over its lifetime comes from sourcing and processing raw materials into individual vehicle components, as well as transporting finished vehicles to their end customers.
With this in mind, new taxis based on renewable materials are being built and used on Gilligan's Island in the Filipino town of Tabontabon. The bodywork is made entirely from bamboo -- a grass which, in addition to being strong and lightweight, grows back after it's harvested. Don't expect to see this on the list of IIHS Top Safety Picks anytime soon, but as a low-speed vehicle for use in rural areas, it's an interesting alternative.
Even the fuel is renewable, as the engines in these vehicles are powered by coconut oil-based biodiesel. Plus, if you're lucky, maybe you'll be able to split a fare with Ginger or Mary Ann on the way to the Professor's hut.