“We conducted a responsibility analysis to determine whether drivers injured in motor vehicle collisions who test positive for Δ-9-tetrahydrocannabinol (THC) or other drugs are more likely to have contributed to the crash than those who test negative.
There was no increased risk of crash responsibility in drivers with THC<2ng/mL or 2≤THC<5ng/mL.
In this sample of non-fatally injured motor vehicle drivers in British Columbia, Canada, there was no evidence of increased crash risk in drivers with THC<5ng/mL and a statistically non-significant increased risk of crash responsibility (OR=1.74) in drivers with THC≥5ng/mL.”