“Prior evidence suggests the potential for population-wide effects of the annual cannabis celebration on April 20th (‘4/20’), but evidence to date is limited. Across all years we found little evidence to distinguish excess drivers involved in fatal crashes on 4/20 from routine daily variations. There is little evidence to suggest population-wide effects of the annual cannabis holiday on the number of drivers involved in fatal traffic crashes.” https://www.ncbi.nlm.nih.gov/pubmed/30696698