and jonathan segal and jonathan with carnegie university. allison, one question that has been asked many times now there is another substance that you have to worry about people using and driving, part of the challenge being that there is no test that is reliable as a breathalyzer for alcohol when it comes to thc in the system and trying to determine how long someone remains impaired after smoking. >> we do have a learning curve when it comes to thc on driving. there are political studies that suggest guidelines for standards. that's what we looked at when we established a per se standard for active thc. when i say active thc, there is the active thc that causes impairment, and the enactive metabolized that will show up in workplace tests for example. our workplace does not apply to the inactive standard but only to the active standard. >> now in the case of alcohol, it's been said, well, my whole life i guess, that it effects different people in different ways, different weights, different body types, different personal chemistry, is that t