It's not much, but roadway asphalt has a springiness to it. As cars roll over asphalt they create indentions about .0003 inches deep. As a result, cars are essentially going up a tiny, yet endless, hill.
"A study by MIT civil engineers found stiffening the nation's pavements could cut fuel use by 3%, the equivalent of 273 million barrels of crude oil, or $15 billion, per year. As a result, CO2 emissions (PDF) would fall by 46.5 million metric tons per year (more than Oregon emits from burning fossil fuels annually)," writes Coren.
The research by Mehdi Akbarian and Franz-Josef Ulm of MIT will appear later this month in the Transportation Research Record. The researchers insist that the cost of replacing roadway surfaces would pay for itself over time. A statement from MIT indicates "...state departments of transportation would save money while reducing their environmental footprint over time, because the roads won't deteriorate as quickly."
Thanks to Jessica Brent