How many traffic fatalities can be attributed to cannabis each year in the US?

Kamer and Warshafsky (IJDP, 2026, 148, Article 105110) have estimated that the recent use of cannabis by US drivers contributes about 5000 deaths per year to the road toll. Part 1 of this Commentary describes the mathematics of the estimation equations. Two clear errors in Kamer and Warshafsky's estimations are identified in Part 2. When corrected, the predicted annual number of cannabis-attributed traffic fatalities falls from about 5000 to about 3550. In Part 3, the focus is broadened to cover some of the factors that should be considered when selecting the most valid values for the variables in the estimation equations. In particular, the co-use of alcohol must be taken into account when measuring the prevalence of cannabis in traffic fatalities. When more appropriate values are used for the variables, the estimated number of cannabis-attributed fatalities falls to below 2000. And it is within the bounds of plausibility that the number could be close to zero.