MIT models tyre-road interactions to reduce fuel consumption

ERJ staff report (DS)

Cambridge, Massachusetts - New research shows that a rigid road surface can help reduce fuel consumption due to rolling resistance.

A new study by civil engineers at MIT shows that using stiffer pavements on US roads could reduce vehicle fuel consumption by as much as 3 percent - a savings that could add up to 273 million barrels of crude oil per year, or $15.6 billion at today's oil prices. This would result in an accompanying annual decrease in CO₂ emissions of 46.5 million metric tons.

The study, released in a recent peer-reviewed report, is the first to use mathematical modelling rather than roadway experiments to look at the effect of pavement deflection on vehicle fuel consumption across the entire U.S. road network. A paper on this work has also been accepted for publication later this year in the Transportation Research Record.

By modelling the physical forces at work when a rubber tyre rolls over pavement, the study's authors, Professor Franz-Josef Ulm and PhD student Mehdi Akbarian, conclude that because of the way energy is dissipated, the maximum deflection of the load is behind the path of travel. This has the effect of making the tyres on the vehicle drive continuously up a slight slope, which increases fuel use.

Stiffer pavements - which can be achieved by improving the material properties or increasing the thickness of the asphalt layers, switching to a concrete layer or asphalt-concrete composite structures, or changing the thickness or composition of the sublayers of the road - would decrease deflection and improve fuel consumption.

“We're wasting fuel unnecessarily because pavement design has been based solely on minimising initial costs more than performance - how well the pavement holds up - when it should also take into account the environmental footprint of pavements based on variations in external conditions,” Akbarian says. “We can now include environmental impacts, pavement performance and - eventually - a cost model to optimise pavement design and obtain the lowest cost and lowest environmental impact with the best structural performance.”

The researchers say the initial cost outlay for better pavements would quickly pay for itself not just in fuel efficiency and decreased CO₂ emissions, but also in reduced maintenance costs.

This research was sponsored by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation with the goal of improving the environmental footprint of that industry.

“This work is not about asphalt versus concrete,” Ulm says. “The ultimate goal is to make our nation's infrastructure more sustainable. Our model will help make this possible by giving pavement engineers a tool for including sustainability as a design parameter, just like safety, cost and ride quality.”

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Press release from MIT