Researchers throughout the United States as well as many other countries are looking for ways to reduce humanity's environmental impact. Normally the studies look at new sources of energy or reclamation programs, but some take a different approach. Researchers at MIT created the first mathematical model of roadways and found a phenomenon that, while difficult to empirically measure, could be costing 273 million barrels of oil each year.
If you watch the rails a train moves on you will notice the steel bends beneath the weight of train cars. This deflection, though less, occurs under the wheels of our cars too and makes driving similar to walking in sand. With each heel-to-toe step, the sand gives way beneath our feet, causing us to have to step up slightly, like we were climbing uphill. Going uphill takes more energy, which means more fuel when talking about cars.
Fortunately, there is a reasonably easy solution to this; make stiffer roads. This can be accomplished a few ways, from changing the composition of the road top to just making it or the road's sublayers thicker. As roads have to be repaved roughly every twenty years, this could be done when the time comes. Of course such changes to the design would then mean the road has a higher initial cost, but as the researchers point out, firmer roads will require less maintenance, so the changes can save money in the long run. Of course the savings in fuel and emissions can also make the changes worth the investment.