The clickety-clack noise a train makes when traveling down the tracks can be a soothing sound. But hearing that same noise while driving on the interstate is annoying. For me, it’s partly because it gets me to thinking about how the road was paved and how the breaks in the pavement are slowly, but steadily having a negative effect on the fuel efficiency of the thousands of vehicles passing over it every day.

Pavement smoothness is a key factor in improving fuel efficiency, especially for heavy trucks. The smoother the pavement, the less energy (fuel) is needed to propel the truck down the road. Every crack and dip in the surface creates a small amount of resistance, requiring an equal increase in force to keep the truck traveling at the same speed.

Even the type of surface can make a difference. Asphalt is more flexible than concrete. So when it flexes as the truck is rolling, there’s more energy of that truck put into the pavement and less propelling it forward. This impacts fuel economy and results in more carbon emissions. Fuel economy can be improved by simply increasing density of the asphalt by as little as 1%.

Obviously, each individual incident of resistance is miniscule, but it adds up over the course of millions of miles. A study published in 2006 by the National Research Council Canada found that trucks traveling on rigid pavements consumed an average of 3.8 percent less fuel than those on flexible surfaces. As fuel prices steadily grow, it’s important to find ways to assist drivers in easy-to-manage ways.

This is another example of how, in the long haul, even slight changes in design can make a big difference.