Interesting results, but the policy recommendations seem like killing an ant with a sledgehammer.
In the first study of its kind, Lawrence Berkeley National Laboratory (Berkeley Lab) researcher Alan Meier, working with Yuche Chen of the National Renewable Energy Laboratory, have estimated the fuel consumption penalty of this popular and fast-growing vehicle add-on. They found that in 2015, roof racks nationwide were responsible for 0.8 percent of light-duty vehicle fuel consumption, or 100 million gallons of gasoline.
Their study was published recently in the journal Energy Policy in a paper titled "Fuel consumption impacts of auto roof racks." In addition to projecting the fuel consumption penalty into 2040, at which time usage of roof racks is estimated to increase by about 200 percent in the United States, they also calculated how effective various policy and technology measures would be at mitigating the penalty.
"A national perspective is still needed to justify policy actions," the authors write. "For comparison, the additional fuel consumption caused by roof racks is about six times larger than anticipated fuel savings from fuel cell vehicles and 40 percent of anticipated fuel savings from battery electric vehicles in 2040."
"These results suggest that some fuel-saving policies should focus on reducing the number of vehicles driving with empty racks," the researchers write.
So next they analyzed the impact of possible policy, technology, and behavior changes. For example, manufacturers have found that it is possible to make roof racks with greatly improved aerodynamics. A policy to require energy labeling of roof racks could spur greater changes, the researchers note.
Even greater energy savings would come from removing roof racks when not in use. Meier notes that they could be designed so as to be easier to remove. The researchers estimated that a government policy to minimize unloaded roof racks (admittedly extreme) in combination with more energy-efficient designs would result in cumulative savings of the equivalent of 1.2 billion gallons of gasoline over the next 26 years.
Or we could just increase the gas tax and let the market take over.
Read more at: http://phys.org/news/2016-04-roof-racks-fuel-economy.html#jCp