Pavement features are a crucial factor when it comes to fuel consumption of vehicles. New research suggests that by introducing minor changes in the design of roads, the fuel consumption of trucks can be highly reduced, a fact that would benefit both the economy and mitigate carbon dioxide emissions.
Regarding future traffic loads, prediction models suggest that car routes will be slightly reduced, however, the total mileage of delivery trucks will be increased, a fact that shows an urgent need to focus on establishing the ideal road conditions for big vehicles.
Scientists from the Massachusetts Institute of Technology (MIT) collected and analyzed pavement data from U.S. roads that included surface properties, road lengths and utilization and climate conditions. After examining the data, they concluded that a key factor that significantly affects the fuel efficiency of vehicles is the stiffness of the road. Actually, they found out that the stiffer the road, the more fuel is saved.
The reason behind this pattern is that nonrigid surfaces tend to deform under heavy loads induced by truck thus creating a small concavity. This small barrier may not seem important but it needs extra energy for the truck to overcome it, thus, increasing fuel consumption. It is like trying to run either on a rigid surface or on sand. In the second case, running is more difficult thus, it requires more energy. "When we as individuals walk on pavements, they seem like perfectly rigid things. The are not responding to us. But for trucks, that is not the case. There is enough of a deflection in that surface that some amount of energy is expended to overcome the little divot that you create as you drive along,” Randolph Kirchain, co-author of the study and a Principal Research Scientist in the Materials Research Laboratory of MIT, stated.
Considering the technical difficulties that need to be addressed in order to make pavements stiffer, scientists state that this is not a critical issue. There are many techniques to increase the stiffness of pavement including:
- Adding synthetic fibers or carbon nanotubes in the asphalt mixture making it much stiffer at a low cost.
- Changing the aggregate size distribution of the mixture making it denser.
There is also another approach to address this issue but it would require a radical change. This suggests the utilization of concrete instead of asphalt in road pavements. Concrete is more expensive but it is also stiffer and more durable. Therefore, it would be equally or more beneficial than asphalt considering the whole lifespan of a roadway project. Moreover, concrete does not deform under high temperatures whereas asphalt experiences deflections under these conditions and needs to be constantly repaired.