>>>It would be quite illegal to demand for such a test in Belgium.
>>
>>Although for people driving truck, bus or a crane such a test would be reasonable from my POV
>
>Don't they already have booze test? Add this, but make it stick - i.e. show current intoxication, not traces from months ago.

Fully with you on the month scale, but as THC sometimes leads to recurrent highs even with no additive intake, I'd argue to base it not on current tox level but on possibility of not clear thinking.