Every year, 60% of the world's oil is used for transportation. It's pretty self-evident that any consumption reduction program has to address private automobiles in particular. There have been many ideas put forth, such as hydrogen or compressed air powered cars, I think this misses the point, which is efficiency. Cars as a system of transport are very inefficient in just about every regard. The problem with the alternative locomotion crowd, who tries to find other ways of making their car/truck go, is that they are trying to keep a dinosaur system alive.
Let's start with the road itself. Roads and highways are extremely expensive. A similar sized railroad costs about 1/10 the price of a paved road to build and maintain. Secondly, compare the rolling resistance/load capacity of a typical railroad to asphalt. As a tractor-trailer is loaded to capacity, it's rolling resistance increases dramatically. A couple horses can almost pull a railcar with 50,000lbs on a level grade. To sum up, the rubber tire/asphalt road is an efficiency nightmare.
Now that we've discredited the road, lets look at the vehicle. Even with an alternative engine, the average car is moving almost a ton of hardware along with its typical single occupant. Throw in traffic, which is lots of stop and go and all you've done with your alternative engine is create a different food for your beast to devour.
How did this inefficient transportation come about:
http://www.lovearth.net/gmdeliberatelydestroyed.htm
The steel wheel on steel rail was created originally so as to save wear and tear on horses. Then came the steam engine. Again, rolling resistance/load capacity were key. The electric trolley was a natural evolution of the horse drawn omnibus. The amount of energy required to move a trolley full of patrons is probably comparable to the energy expended by your car as you drive it an equivalent distance. There are disadvantages to rail, such as steep hills, but these can be cut through.
As we head toward Peak Oil, it would behoove us to throw out the fantasy of maintaining the rubber tire/asphalt roadway system. We already have an alternative that works which we allowed big business to take away from us years ago.