Before we settle on a legal driving limit of marijuana intoxication, scientists are still working out how we could even gauge it:
The Swedish company SensAbues is offering something of a fix. A study published in the Journal of Breath Research last week found that its proprietary breath-testing device can detect recent use of a wide range of drugs, including prescription meds, cocaine, and marijuana. … [But the] device only detects the presence of marijuana, not whether a driver has consumed enough to be impaired. And even more problematic from a cop’s point of view: The filter samples have to be analyzed in a lab—which means no instant field results.