PhotoFuel-efficient cars are great, but they're not doing much for highway construction and maintenance. Since they burn less -- or, in the case of electric cars, no -- fuel, they're paying less in gas tax at the pump, which is putting a dent in states' highway funds.

Some states have been thinking about charging a surtax for plug-in vehicles, but in a paper to be published in the August issue of Energy Policy, researchers at Indiana University-Purdue University Indianapolis say that approach is misguided. 

At least eight states have imposed a vehicle registration fee, ranging from $50 to $200, for alternative-fuel vehicles: Colorado, Georgia, Idaho, Nebraska, North Carolina, Virginia, Washington and Wyoming.

Virginia also penalizes purchasers of new vehicles with an extremely high property tax rate that can cost $1,000 or more per year. This discourages consumers from buying newer, fuel-efficient cars, but counties have grown accustomed to the money and don't want to give it up.

Only 1.6%

Despite the discriminatory penalties, researchers say that plug-in cars are responsible for only 1.6 percent of the erosion in gas tax revenues.

Other factors identified by Jerome Dumortier and Seth Payton, assistant professors in the School of Public and Environmental Affairs, and Matthew Kent, a former graduate student, are the increasing fuel efficiency of vehicles in general and the failure to adjust the gas tax for inflation.

"The lesson for policymakers is that plug-in vehicles do not contribute significantly to the funding shortfall in the short- and medium run, and a supplemental tax on plug-in vehicles would generate only a small percentage of additional revenue," Dumortier said. "We show that the majority of the funding shortfall is due to the non-adjustment of fuel taxes and the increase in fuel efficiency. Thus a registration fee would not alleviate the funding shortfall."

Besides, penalizing owners of plug-in vehicles flies in the face of policies intended to promote their use due to concerns about energy independence, energy efficiency, and greenhouse gas emissions, Dumortier said, and doesn't take into account the extremely small number of electric cars on the road.

In the long run, the United States should shift its road infrastructure funding away from gasoline taxes to an alternative system that should be, as most research suggests, based on vehicle miles traveled, according to the paper. 

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