MIT study finds stiffer road surfaces would cut fuel consumption

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An MIT study has found that soft road surfaces increase fuel consumption, making cars less ful efficient. Image from Wikimedia Commons.

A great number of things factor into fuel consumption, including the state of the engine, tire inflation, driving style and also, according to an MIT study, surface pavement. A recent paper from MIT found that stiffer surfaces could lead to a significant boost in fuel economy for motorists.

More incentive to pay for road repairs

The nation’s highway system is known to be in bad shape. Every year, state governments wrestle with needing more money to fund repairs. The federal government does as well.

However, as with any public utility, the public doesn’t always want to pony up even if a repair is drastically needed. Another reason people might want to pony up for highway repair and improvement projects, according to Wired magazine is that it will save at the pump. A study from the Massachusetts Institute of Technology found as much.

Efficiency is a product of output versus input

The “efficiency” of a machine is a proportion of mechanical output versus the input of energy into the machine. More resistance between output and input reduces efficiency. With cars, the more “work” an engine has to do to move the vehicle a given distance, the less fuel efficient it is.

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Part of that resistance, according to a study Dr. Franz-Josef Ulm of MIT’s civil engineering department and Mehdi Akbarian, a Ph.D student at the college, is from the rigidity of road surfaces. Using Department of Transportation figures detailing the conditions of 5,643 sections of highway nationwide, they were able to model the relative resistance encountered by passenger cars and trucks on these sections of pavement.

They found many roads are relatively “soft,” which, like sand, means greater resistance to the tire’s grip, called “rolling resistance.” More rolling resistance means more energy is expended to travel a given distance, increasing fuel consumption.

A stiff penalty

The authors, according to Science Daily, estimate the nation’s vehicles are collectively using an extra 7,000 to 9,000 gallons per mile, per lane on roads with high traffic every year. They estimate an 80 percent reduction on those roads is possible by stiffening road surfaces.

All told, Akbarian and Ulm estimate an overall fuel consumption improvement of 3 percent nationwide is possible, adding up to a savings of 273 million barrels of oil and $15.6 billion at current prices. The overall reduction in carbon dioxide emissions would be up to 46.5 metric tons of the gas expelled into the atmosphere.

The authors advocate more layers of asphalt and concrete to thicken road surfaces and thereby reduce “deflection,” or the gradual compression of road surfaces by a constant stream of vehicles driving over it. They maintain roads would last longer, saving money over the long run. However, the cost of doing so would be considerable. The nation’s highways, according to the Detroit Free Press, were underfunded by at least $137 billion per year as of 2009, when a federal task force examined the need for repairs. By 2035, state and federal highways will need almost $2 trillion of work if repairs go unfunded.



Science Daily

Detroit News

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