Anyone with an active lifestyle will likely own a vehicle with roof racks prepped to carry bicycles, cargo boxes, and other outdoor toys. There have been numerous reports regarding the negative effects roof racks have on fuel economy, but a recently study from the Lawrence Berkeley National Laboratory claims roof racks were responsible for the consumption of around 100 million gallons of fuel in the U.S. last year.
The Berkeley Lab says its study was the first to extensively look at the national impact of automotive roof racks, which often hurt fuel economy due to additional aerodynamic drag. It estimates that roof racks can reduce fuel economy on vehicles by 0 to 25 percent depending on the racks' configuration and if they are loaded or not. Based on that estimate, the researchers claim roof racks were responsible for 0.8 percent of light-duty fuel consumption in the U.S. last year, or approximately 100 million gallons of gas.
To collect data, researchers surveyed users in online forums. Next, they utilized the crowdsourcing website Amazon Mechanical Turk to hire workers who were assigned to highways nationwide to conduct video surveys of vehicles equipped with roof racks.
The researchers found that roof rack usage is increasing and should continue to grow by an additional 200 percent by 2040. The study also discovered that vehicles with unloaded racks traveled four to eight times as many miles as those with loaded racks.
Researchers note that a number of behavioral, policy, and technology changes could lessen the impact roof racks have on fuel economy. Owners, for example, are encouraged to remove racks when not in use, while legislators should consider "energy labeling" requirements to better inform consumers. Finally, automakers could develop technology to make racks more user-friendly and aerodynamic.
Source: Lawrence Berkeley National Lab