One thing I wonder about though, is the wheel. Why are there no animals with wheels? It may seem like a stupid question to the layman, but to an engineer, it's a most puzzling matter.
Why do creatures (actually, creature may not be the most appropriate question here, because a creature has to be created... never my mind) have legs? A wheel is a much easier means of transportation, no?
My argument is based upon the fact that a wheel is so much simpler then a limb with a multitude of pieces. Oh's well, similar to the ornithopter, only few men bother putting the effort into making a machine that walks instead of rolls. For the rest of us laymen, we shall stick to wheels.
Auto mobiles, though not a very common form of transportation, are a great asset to any individual that owns one. The only people that own them are the highly rich that can afford to purchase such a vehicle, or the highly intelligent that know how to build them. They commonly appear to look like Duesenburgs and Morgan Motor cars.
The Auto mobiles that are owned by the wealthy commonly have internal combustion engines. Due to the scarcity of fossil fuels, they are more commonly powered by biodiesel.
The cars made by the crazy genius's are hardly ever powered by an internal combustion engine. Because of the lack of funds, they are forced to find other, more economic means of power. Sterling and steam engines are the most common used by these folks. They heat the sterling engines with sunlight or friction (as the vehicle actually gets moving). Once in a while you'll see an automobile powered by solar energy.
Now, there are taxi vehicles through out the large cities that are powered by wireless electricity that's transmitted throughout.
One of the most common forms of transportation for both people and cargo.