In all situations, the most important part of finding the best solution is the part usually given the least thought--defining the problem to be solved.
The most fuel efficient car that can be built, is still a poor solution to the real problem, which is in transporting people and cargo quickly, efficiently and safely.
The single biggest factor affecting fuel efficiency in America is the dismantling of the railroad system in favor of automobiles and trucks.
Individually powered and guided, vehicles are, by nature, inefficient, dangerous and slow especially for long-distance travel. The infrastructure required is extremely expensive on a per ton of material transported.
This has happened because despite the name "Department of Transportation," the transportation system has never been treated as a system and has been semi-functional at the whim of various special interest groups.
It is now, outside of major urban areas, nearly impossible to use mass transportation to journey with any degree of convenience within the US.
Because transportation is a hodgepodge of methods of transport which have no designed interface to assist in moving between various forms.
While you CAN travel using mass transit, it is usually far from convenient either in placement of terminals or scheduling.
Most long distance travel occurs using aircraft--one of the least fuel-efficient means available, and due to inefficient and ineffective security requirements, time-wise it is not even faster than travel by automobile for flights less than 1 hour flight time..
Additionally, few airports are well-served with mass-transit access, and fewer still are accessible on foot or bicycle.
Thus, when traveling by air, travelers have to arrange transport through one of a number of means, of which only a very few may be available.
Automobile is the only choice available for vast number so people. Among the disadvantages of this are the fact that you must leave an expensive car stored with little security available for theft for the duration of your round trip.
Because few of these decisions which affect transportation are made based upon technically good solutions, but rather by the politics involved with special interests attempting to influence the design, placement and financing of all major transportation projects.
This leads to "freeways to nowhere" and routes which are under or over utilized, and over-priced, under-specified construction often using both inferior materials and workmanship--preparing the way for lucrative maintenance contracts.
The use of long-haul trucking is far less efficient than rail, and is subsidized because trucking companies do not pay for the damage that heavy trucks inflict upon highways--roads which might last decades w/o major maintenance if subjected only to automobiles, are badly damaged in less than 5 years.
This subsidization is a major factor in the demise of the rail system.
A large percentage of our rail system has been dismantled--although most of that mileage could be rebuild quite rapidly as the rail-beds are still extent. Required would be new ballast, ties, rails, bridges & road crossings. Thanks to modern rail equipment, this construction can be performed far faster than the original work.
After water travel, rail is the most efficient means of moving over moderate to long distances.
If we are to reduce energy use by increasing fuel efficiency, we need to stop treating individual means of transport as individuals and begin treating them as parts of an entire system.
