So the testing has to be convenient for the state, or people lose their rights? The test exists, it's part of the legislation in the state of WA. What is wrong with a field sobriety test, that has been used for alcohol for generations? Doesn't that measure impairment? If not, a blood test of active THC in the blood can be done. The research HAS been done, it's just that our government didn't like the conclusions. A search of "1993 NHTSA Marijuana" will bring it right up. It doesn't cause driving impairment. Canada and the UK's studies concur. We should make caffeine illegal to drive under the influence of, too, right? Why not? Because there is no proof of impairment? EXACTLY. It's the same with marijuana. Show us the proof of impairment.