“Since 1990, 11 states have passed so-called zero-tolerant per se drugged driving laws which make it illegal for one to drive with detectable levels of a controlled substance in his or her system. Five additional states have passed similar laws specifying non-zero limits for controlled substances or their metabolites. Using state-level data from the Fatality Analysis Reporting System (FARS) for the period 1990-2010, authors examined the relationship between the adoption of controlled substance per se thresholds and overall incidences of traffic fatalities. They found that the relationship is statistically indistinguishable from zero.”
