The White House recently announced the development of fuel economy standards for heavy-duty trucks that will take us well into the next decade. However, it is time to look not only at the efficiency of cars and trucks on the road, but to the road itself for fuel economy and emission reductions.
The Massachusetts Institute of Technology (MIT) is bringing rigorous data to the debate on the role that pavement-vehicle interaction (PVI) plays in the environmental and economic costs of the nation’s roadways.
Research by the MIT Concrete Sustainability Hub (CSHub) shows that PVI — related primarily to road stiffness and roughness — has a measurable effect on vehicle fuel consumption. That effect is significant over time and thus essential to the analysis of the lifetime environmental impacts of road projects using life cycle assessment (LCA) tools.
The United States’ transportation network is responsible for about one-third of national energy consumption and greenhouse gas emissions. As the network ages, the impact of PVI on greenhouse gas emissions worsens. Meanwhile, infrastructure funding remains significantly below what is required to improve conditions and performance. With the Highway Trust Fund forecast to go bankrupt next year, these findings bolster the case for increased infrastructure spending as Congress prepares to debate a new long-term transportation bill.
To ensure the sustainability of our roadways, policymakers and construction professionals must carefully analyze pavement designs’ cost and environmental impact throughout their entire lifespan by using life-cycle tools during the planning stages of road projects. For LCA to be effective, it must be based on the most accurate models possible, including those that analyze the effects of PVI.
The PVI debate stems largely from the variability in previous experimental investigations of fuel consumption on different pavement types. The CSHub’s models help illuminate the key drivers of PVI and allow pavement engineers to incorporate them into their design decisions. They have been used to predict that stiffer pavements could reduce fuel consumption up to 3 percent for the U.S. pavement network — a savings that could add up to 273 million barrels of crude oil per year. This would result in an accompanying annual decrease in CO2 emissions of 46.5 million metric tons.
CSHub researchers also evaluate the impact of pavement roughness on fuel consumption. A sample case study showed a significant impact on fuel consumption due to roughness — an increase of 30,000 gallons of fuel per mile over a 14-year test period. Other academic institutions as well as some state departments of transportation are conducting experiments that will help to validate and refine MIT’s PVI-related research. MIT is collaborating in several of these efforts.