"How to Increase Vehicle Fuel Efficiency" is the Wrong Question

I saw this story on Viridus News about how a group has organized around the goal of doubling vehicle fuel mileage by the year 2050 (the group is called 50by50) and has some significant backers.

The only problem with this, as I see it, is that it too narrowly defines the problem. 50by50 has a goal to double fuel efficiency of *new* *cars*. That leaves out old non-cars. According to Wikipedia, there are roughly 251 million registered vehicles in the US. Of those, 135 million are classified as "cars" plus there are an additional 99 million "other 2 axle, 4 tire vehicles" which presumably are SUVs and pickup trucks (which are exempt from a lot of the "car" rules). Further, each year there are sold about 8 million new "cars" or about 3% of the total fleet. That means that a doubling of fuel efficiency will have a small but measurable impact on overall vehicle fuel consumption.

So the right question is, "how can we reduce vehicle fuel consumption?" Asked that way, there are many things we can do that will have a bigger impact in a time frame much shorter than 40 years. Here are some examples (off the top of my head):

(1) GPS navigation. Pass a regulation that every new vehicle sold in the US must have a GPS navigation system installed in it. Make it similar to the regulation requiring catalytic converters and air bags. Most car makers already have this as an option on their vehicles so the cost to implement this change would be minimal. Aslo create a $300 tax credit for purchase of retrofit GPS systems that would effectively make these "free" for consumers. The net result would be that a good portion of the 10-20% of all miles driven in the us (the "lost" miles) would be eliminated. Over night consumption of gasoline and diesel would drop considerably.

(2) Road construction. Amend the stimulus bill so that the $100-odd billion dollars earmarked for highway construction must take into account vehicle efficiency. Little attention is paid in designing roads and bridges to vehicle efficiency. These projects are prioritized and designed for cost, safety, longevity, etc. but not for vehicle efficiency. Road surfaces, placement, lights, traffic management, etc. all have an impact on the fuel consumed by automobiles so while we're spending all this money let's design efficiency in.

(3) Tires. Pass a law that puts an tax on tires based upon a certification test on efficiency. Obama took heat during the campaign last year for saying that proper inflation of tires is something everyone can do to fight the high cost of gasoline. In fact, if everyone properly inflated their tires it would save 2-3% of total vehicle fuel consumption, a huge number. Also, many tires are incredibly inefficient. Those wide, low profile flashy tires consume a lot of fuel. It's fine if you want them, we should just place a big tax on them.

As with most problems relating to sustainability, my advice is to define the problem in its broadest, most fundamental terms and then look for solutions that solve it. Increasing fuel efficiency of new cars is part of the solution, but in all likelihood a small part.