If even a Prius isn't energy-efficient enough for you, maybe this'll be more to your liking. The Twike runs on rechargeable NiCd (NiMH) batteries and will carry two passengers along at speeds up to 80 kilometers per hour (55mph), with a range of 80km per charge. You can actually even extend that an extra 30% with its "hybrid pedal power adaptation", a technology first pioneered by Prof. Flintstone. When it runs out of juice you simply plug it into a regular household socket for about two hours. No word yet on when you'll be able to get your hands on one, or how much it'll cost, but four Twike's are currently on a cross-continent trek (we're guessing Europe) to show off the energy-saving technology.