Cops can use a breathalyzer to test if you're drunk... but what if you're high? With marijuana legal in two US states now, Trace shows us the test law enforcement plans to use to see if you've been driving stoned.

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The Confusing Science of Stoned Driving
http://motherboard.vice.com/blog/the-confusing-science-of-stoned-driving
"The trick, when it comes to marijuana and driving, involves determining what exactly "dangerously impaired" means."

Cannabis / Marijuana
http://www.nhtsa.gov/People/injury/research/job185drugs/cannabis.htm
"Marijuana is a green or gray mixture of dried shredded flowers and leaves of the hemp plant Cannabis sativa. Hashish consists of resinous secretions of the cannabis plant."

Smoke and Mirrors: Driving While High on Marijuana Doubles One's Chances of a Serious Car Crash
http://blogs.scientificamerican.com/observations/2012/02/09/smoke-and-mirrors-driving-while-on-marijuana-doubles-ones-chances-of-a-serious-car-crash/
"Booze is behind an estimated 2.1 million car accidents each year in the U.S.-which cause almost 11,000 traffic fatalities annually."

DWI Versus DW-High
http://www.slate.com/articles/health_and_science/explainer/2011/11/does_marijuana_make_you_a_more_dangerous_driver_than_alcohol_.html
"Is it more dangerous to drive drunk or stoned?"

Determining if you're driving stoned: What police will look for
http://www.katu.com/news/local/Determining-if-youre-driving-stoned-What-police-will-look-for-washington-marijuana-law-181936761.html
"When possession of small amounts of marijuana becomes legal in Washington in three days, there will be a DUI limit of five nanograms of THC that you can have in your blood."