If you live anywhere near a dirt road or a Subaru dealership, you've likely seen your fair share of roof racks on the road. Whether laden or unladen, racks are great for hauling more crap than your vehicle normally could carry. But they're not perfect. In fact, they're actually burning through gasoline at a ludicrous rate.

Researchers from Berkeley Lab and the National Renewable Energy Lab teamed up for a first-of-its-kind study that looks at the environmental impact of roof rack use in the US. The group relied on a wealth of data, including forums, highway video surveys and crowdsourcing.

According to the study, published in the journal Energy Policy, roof racks were responsible for 0.8 percent of annual light-duty vehicle fuel consumption in 2015. While that might not sound like much, it amounts to about 100 million gallons of gas, just to move roof racks down the road. It's only going to get worse, as well, as the study estimates roof rack use will increase by 200 percent by 2040.

"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," the group wrote in a press release.

The reasoning is simple -- aerodynamics. Roof racks create drag, which requires the car to exert more effort to cut through the air, wasting fuel in the process. The study notes that roof racks can reduce fuel economy by up to 25 percent.

The easiest solution to this problem is to remove the roof rack when it's not being used. Yes, that can be a pain with some racks, and you might lose some street cred in the REI parking lot, but unless you feel like shelling out more and more money at the gas pump, it's probably for the best.