Drive around town, and you’ll see hundreds of empty roof racks sitting unused atop daily driven vehicles. They may not be the most extreme aerodynamic impediment, but neither are these things boosting the average driver’s ability to outsmart the pump, and now there’s proof.

A new study has shown that around 100 million gallons of gasoline were wasted last year alone due to roof racks, and a lot of it has to do with the unused ones. While certain attachments are more prone to damaging a vehicle’s fuel economy than others, the extreme of an added 25% drag efficient is fortunately not always the case. But according to researchers Yuche Chen of the National Renewable Energy Laboratory and Alan Meier of Berkeley, “the use of roof racks is expected to climb 200% by 2040.”

This may sound OK, but the findings also show that the roof racks of the future are also expected to “use six times the amount energy fuel cell vehicles are expected to save, and 40% of fuel savings from EVs.”

According to a report by Autoblog, the authors also say that “these results suggest that some fuel-saving policies should focus on reducing the number of vehicles driving with empty racks.” Since automakers and aftermarket manufacturers probably don’t have engineering more aerodynamic racks on their priority list, Chen and Meier suggest that mandatory energy labeling might be the most sound decision.

Making racks more easily removable when they are not needed is another consideration worth weighing, and while shelving unused ones may sound implausible, researchers say that in combination with sleeker designs, it could “save 1.2 billion gallons of gasoline between now and 2040.”

Breaking it down to the bare bones, the EPA says that all this equals out to the elimination of 11.8 million tons of CO2 emissions, or the same amount of crud spewed by 86,717 cars over 26 years. But this is still a finite fraction compared to the bigger pollution picture, and since no one seems to be tripping over themselves to amend it, it’s hard to imagine that there aren’t angles that haven’t been looked at.

“I’ve always been intrigued by energy consumption that was somehow overlooked or ignored,” Meier says. “In this case the fuel consumption of vehicles with after-market accessories isn’t captured in the test procedure.”

Meier and Chen discovered that unloaded cross roof racks driven on the highway were the most commonly overlooked factor, and often made the biggest difference. This surprising discovery was primarily due to the fact that the number of miles racked up with empty roofs was four to eight times higher than that of loaded racks.

So even if policies, technologies, and social behaviors change, how long will this shift take? In short, no one really knows, because for as fantastic as the thought of lowering greenhouse gases and eliminating unnecessary fuel waste is, there are far more pressing automotive matters at play right now.

We say that since most people never use them anyway, dealers should just make roof racks an exclusive option and let the buyer decide — leaving automakers with the task of designing something more lightweight and aerodynamic. This would also save buyers a few hundred bucks at signing, and in turn they wouldn’t have to outsmart the dealer in order to remove a damn roof rack.