in the summer of 2005 i came across the twike. it is more than a bike, with some of the power and protection from the elements that you get in a car. youtube has videos of twikes doing things like driving onto a ferry.
its one steerable wheel in the front two powered wheels in the back. from what i've read the tadpole or two steerable wheels in the front, one powered wheel behind, is a better layout. the current electric cars are trying to be gas-cars with electric motors. the twike keeps the most efficient and reliable, although low-power, source of energy in the loop - the human body.
i love the pull-down enclosure and mine is going to have general purpose computers on touchscreen displays. what would it take for a DIY twike? a recumbent bicycle with an enclosure, electric motor in the drive train, and batteries. im sure thats been done and its almost too small. invisible on the roads where the twike is very-small-car sized. a two seat model is fantastic.
a friend in seattle welded together a tandem bike from two bike frames. i wonder how much harder it is to make a twike-like frame.