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MIT Study: Traffic Jams Magnify How Roads Affect Fuel Consumption

Matt Ball on August 14, 2015 - in Analysis, Corporate, Roads

It seems all too obvious that getting stuck in a traffic jam will increase your car’s fuel consumption. After all, the engine is running but you are going nowhere.

Less obvious is how traffic jams affect other factors in fuel efficiency, such as the condition of the road itself.

Researchers at the Massachusetts Institute of Technology’s Concrete Sustainability Hub addressed this issue in a recent study. Their findings suggest that traffic jams magnify the impact of pavement deflection, but drastically reduce the effect of roughness on fuel efficiency and resulting greenhouse gas emissions.

The effect of pavement on vehicle fuel consumption is well documented.

Research by MIT and others found that deflection of the pavement under traffic increases rolling resistance and decreases fuel efficiency.  Such deflection can be significant. Rigid pavements can reduce fuel consumption by as much as 3 percent over flexible pavements.

Another factor is pavement roughness, which also reduces miles per gallon.

Equally well established are the opportunities for reducing the environmental impacts of highway travel. The U.S. transportation sector burns over 174 billion gallons of fuel each year, accounting for 27% of total greenhouse gas emissions.

But how does traffic congestion fit into pavement-vehicle interactions and strategies to reduce fuel consumption?

Quantifying its impact will result in a more realistic look at the impact of roads.

According to the Hub’s research brief, traffic corresponds to either free flow conditions, where all the vehicles travel at the speed limit, or congested flow, in which traffic jams appear.

Researchers incorporated traffic simulations into their model for calculating the effects of roughness and deflection. Findings point to significant impacts on both factors.

In the congested traffic, the deflection-induced fuel consumption is up to 3.5 times higher than in free-flowing traffic.

Yet roughness-induced impacts were ten times lower when traffic is congested.

The conclusion: Implementing more realistic traffic distributions into a complete roadway network provides decision-makers with better information about the impacts of pavement conditions on vehicle fuel consumption, especially in regions that experience high congestion.

In the wake of new fuel reduction standards proposed by the administration, MIT research points to the need for a more comprehensive strategy that addresses not only the fuel efficiency of cars and trucks, but also the roads on which they travel.

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