LANSING, Mich. — Researchers at the University of Michigan surveyed nearly 800 medical marijuana users.
The researchers asked about their driving habits for the past six months and more than half reported driving within two hours of taking the drug.
More than half also said they drove while they were a little high and over 20-percent reported they were "Very high" when they were behind the wheel.
The study suggests the state needs clearer guidelines of marijuana doses and how it effects different body types and sizes are needed as legalization sweeps through the nation.
About 270 thousand people in Michigan are legally able to use medical marijuana.
Only California has more. Researchers say the potential for high drivers and any dangers they may pose on the roads is greater.