When it comes to alcohol, there are tests to determine whether a driver gets a DUI. If your blood alcohol level is .08 or above, you cannot be on the road.
However, when it comes to marijuana the rules aren’t so clear. There is no test to determine how stoned you are and marijuana affects everyone differently. That said, it is illegal to drive under the influence and it is illegal to consume pot if you are under 21.
If you are pulled over on suspicion of driving under the influence (swerving, delayed reaction, etc.) enforcement will perform various tests onsite to determine if you might be under the influence. They can also take you in for further drug testing.
(Photo: Frederick Dennstedt)