(TNS) -- WASHINGTON –– The small drones flooding the commercial market are unlikely to cause severe head injuries if they fall out of the sky and strike people, a new study has concluded.

The results are similar to findings earlier this year by researchers associated with the Federal Aviation Administration and offer more justification for opening the door to unmanned operations over crowds.

Researchers at Virginia Tech in Blacksburg, Va., the site of an FAA-sanctioned drone testing facility, concluded that the risks of a catastrophic head injury were less than 5 percent in an impact with a 2.6-pound (1.2-kilogram) unmanned vehicle, according to results published in the Annals of Biomedical Engineering. Larger drones create higher risks of injury, which may limit their uses until other safety standards can be devised, the study found.

“Risk of injury was observed to increase with increasing UAS mass, and the larger models tested are not safe for operations over people in their current form,” the researchers, led by biomechanical professor Steven Rowson, said in the journal article, referring to drones as unmanned aircraft systems.

The risks of a head injury are also greater if a drone falls on a person than if it runs into them while flying, they concluded. Because the FAA defines small drones with the lowest level of oversight as weighing as much as 55 pounds (25 kilograms), the agency may want to reclassify its guidelines to restrict the heavier ones from flying over people, the authors said.

The study focused solely on head trauma and didn’t assess the potential for rotor blades cutting the skin or other injuries.

The FAA had planned to release by the end of 2016 a preliminary outline for allowing at least some drone flights over people. Such rules are needed by multiple industries from network television news shows to drone delivery pioneers, such as Amazon.com Inc. and Alphabet Inc., the parent company of Google.

The U.S. government temporarily put the effort on hold after law enforcement agencies objected, saying there needs to be better ways of tracking unmanned vehicles before they’re unleashed over people.

The Virginia Tech study looked at three models made by China-based SZ DJI Technology Co. The smallest was the Phantom 3, which was flown straight into a crash-test dummy’s head and also dropped on the dummy to simulate falling from the sky.

While the risks from the Phantom 3 were minimal, the potential for injury increased dramatically as drones weighed more. A DJI S1000+ model, an eight-rotor copter weighing 24 pounds (11 kilograms) had an injury risk of about 70 percent in some tests.

The FAA in April released similar results of studies it had financed. “So many people are watching these studies,” Earl Lawrence, director of FAA’s Office of Unmanned Aircraft Systems Integration, said in an interview earlier this year. “FAA needs it to support our rulemaking activities, but so does every other civil aviation authority and interest groups throughout the world."

The agency last year adopted regulations allowing routine small-drone flights for commercial purposes, but restricted them to within sight of the operator, no higher than 400 feet above ground and not directly over people.

©2017 Bloomberg News Distributed by Tribune Content Agency, LLC.

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