Making road surfaces stiffer could improve trucks’ fuel efficiency enough to reduce greenhouse-gas emissions from the transportation sector at little to no cost, a study by MIT engineers has found.

According to Randolph Kirchain, PhD ’99, principal research scientist in the Materials Research Laboratory, driving on a softer road is energy-intensive in the same way as walking on sand. He and his coauthors, MIT postdoc Hessam Azarijafari and research scientist Jeremy Gregory, SM ’00, PhD ’04, say there are several ways to make roadways stiffer: add a small amount of synthetic fibers or carbon nanotubes to asphalt, use a denser overall mix with more rock and less binder, or switch from asphalt to concrete, which is already common in many northern US states.

If 10% of road surfaces were improved each year, they calculated, a total of 440 megatons of emissions would be avoided over 50 years, which is about 0.5% of total transportation-related emissions for that period.