I could be mis quoting some things, but there are different THC metabolites.

The THC-COOH stays in your bloodstream only for a short time after smoking. 4 hours after consumption i think is a time frame I saw somewhere.

The THCa is what they find during drug testing that remains in your system for a very long time.

Read through some of these studies to get a grasp on Marijuana and Driving.
Marijuana And Actual Driving Performance
SoCoMMJ Reviewed by SoCoMMJ on . No more stoned driving -- Colorado is passing THC limits for DUI Colo. may set limits for driving after marijuana use - The Denver Post This is pretty fucked up... I believe the blood level is 5ng/ml. I need to do a bit more research, but I think if you're a fairly heavy smoker (i.e. a few times a day), then your levels are pretty much always going to be at this level or higher. So basically you won't be able to drive ever without risk of getting a DUI. Way to go Colorado!!! What is motivating this law? Is there really a problem with stoned Rating: 5