A new study finds the number of drivers fatally injured in automobile accidents who tested positive for one or more substances is rising, according to U.S. News & World Report.

The study, by the Governors Highway Safety Association, found that 44 percent of fatally injured drivers with known test results tested positive for drugs in 2016, up from 28 percent a decade earlier.

More than half of the drivers had marijuana, opioids or a combination of the two in their system, the study found. Thirty-eight percent tested positive for marijuana, 16 percent tested positive for opioids and 4 percent tested positive for both. Among the drivers tested for alcohol, 37.9 percent tested positive in 2016, down from 41 percent in 2006.