A new study suggests more than half of medical marijuana patients are getting behind the wheel while they're high.

The University of Michigan Addiction Center surveyed nearly 800 medical marijuana patients. 51 percent reported driving a "little high" within the past six months, while 21 percent drove "very high."

"We know that using marijuana can affect things like your coordination, or your reaction time and those are critical functions for driving," said Dr. Erin Bonar with the Addiction Center.

Medical marijuana is legal in 30 states, including Oklahoma. Researchers are developing marijuana breathalyzers and other roadside drug tests.