The blood alcohol content (BAC) in most US states to be considered drunk is typically 0.08, although some states still use 0.1, while 0.05 is when impairment begins for most of these states. All 50 US states are very clear with their drunk-driving laws, but a new trend is about to get underway. Colorado, Washington, Oregon, and Alaska have recently passed fully legalized marijuana. In addition, 24 states have both medical marijuana and decriminalization laws. Another five have just decriminalization possession laws.

Point being is that the legalization of marijuana is becoming more widespread in the US. With that in mind, the question now is how will states determine how much weed an individual can smoke and still be considered a safe and sober driver? The problem is that "there's a significant variation in the minimum acceptable levels of marijuana or its traces in a driver's system," according to the president and CEO of the AAA Foundation for Traffic Safety. There's really no uniformity, unlike with alcohol. Interestingly, one-in-six Americans report that where they live, people think it's just fine to drive just one hour after lighting up.

US government research, however, shows that weed can impair driving abilities for up to three hours. Aside from alcohol, the lines between smoking weed and the effects of other prescription and over-the-counter drugs is quite blurry. Prescription and non-prescription drugs can also hinder one's driving. So how to measure weed? That's the burning question.