This was my point when I said you can find articles to support any position.

I don't know how they could even go about setting limits based on amounts of certain drugs in someone's system. It's not just the presence, and it's not the amount either; it's the effect it has on the person's judgment, reflexes, cognitive functions, etc. Abusers/recreational users (those using for the "high" or psychotropic effect) are the real problem - not legitimate pain patients with established tolerance. Impairment can also stem from emotional stress, fatigue (lack of sleep), pain.

It would make more sense to devise a portable field simulator to test driving ability, but that might open the political hotspot of re-testing elderly drivers, and that may be getting a little

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