Since I dropped a link in the latest Gizmag post, I'm expecting an influx of international visitors.... welcome to my blog! I didn't want to put a bunch of links in my comment, so instead I'm going to weave them all together in this summary post.
When we consider what makes a vehicle energy efficient, two things are more important than anything else: weight and aerodynamics--the lower the weight and wind resistance, the lower the energy required to move. Consider the ratio of cargo weight to carrier weight (in kg): for me and the average sedan, that's about 72.6/1360.8 or 0.053; for me and my electric bicycle, 72.6/18.1 or 4.0; me and a racing bicycle, 72.6/6.8 or 10.7. It is clear that the bicycle represents one of the lightest forms of transportation, and it is thus also one of the most efficient. I am convinced that bicycles can save the world--the outline of my argument in support of this is found in my post titled A Radical Proposal (for any literature fans, yes this is a play on A Modest Proposal).
But the bicycle alone may not be enough, maybe in a sincerely fitness oriented culture, but that kind of mentality takes a long time to develop... technology develops much faster. For instance, the road I live on has a hill with a grade around 10%. In days past I was fit enough to ride my bicycle up worse, but in the time I've lived here I don't recall ever being able to make it up without feeling like I was about to keel over dead. Quite recently I added an electric motor to my bicycle, and despite more than doubling the weight I can haul up that hill in nearly my tallest gear, without even standing up--I've done this almost every day since I got the kit. Also, my legs look better than they have since shortly after I finished my trans-America tour; just because there's a motor doesn't mean I'm not doing any work! I'm going to do a very rigorous overview of electric bicycles at some point in the future, but until then this will have to suffice.
As I mentioned, weight is only part of the battle; the more significant part is wind resistance. The only way to significantly change the aerodynamics of a bicycle is to add a fairing, which generally necessitates the use of a recumbent tricycle. This vehicle is called a velomobile, which is discussed in my post Rise of the Velomobile.
The last part of the puzzle that I mentioned in my Gizmag comment is autonomous navigation and solar roadways. Autonomy is more a necessity for the very heavy and fast every day car, but the benefits of such a system would still be reaped by this ultralight human/electric hybrid. The concept of autonomous transportation and a few different perspectives on energy are covered in depth in the post Intelligent Transportation Systems. The danger caused directly by cars is covered in several posts, notably How Dangerous is the Road?, which also links to information about the very promising solar panel roadway. Solar roadways and roadway to vehicle power transmission are important because they enable significant weight reduction by reducing battery capacity requirements, which leads to further weight reduction by allowing for the use of a smaller motor.
There is still much to be covered (for instance, the average US citizen spends 17% of their income on car related expenses), but not enough time to cover it right now.
Thanks for visiting, please enjoy