Dale, the reason we dont know how long it takes to reach a safe level for mj is for decades the federal govt prohibited unbiased research on pot, they claimed it was a class I drug and therefore bad even though it doesnt fit the guidlines like physical addiction or overdose deaths. There is a sign at the mj dispensary that suggest not driving for 6 hours after using, but as a practical matter there are many drivers who use and there dont seem to be any more wrecks than before it was legal unless you add in alcohol. And there is also a federal law of max highway speed of 75 mph, do you think all drivers observe it?
I dont live in Alabama, but it about half the real world cities and states are not arresting people for having a joint.