Loaded dice: A game theory analysis of drunk driving laws in Brazil.

OBJECTIVE: The aim of the study was to evaluate whether the current legislation would encourage drunk drivers to refrain from taking a breathalyzer and thus avoid jail time.

METHOD: Brazilian traffic laws currently have 3 possible punishments for drivers suspected of driving under the influence: A fine and suspension of license for 12 months if the breathalyzer result is under 0.3 mg/L (by law; a result up to 0.33 mg/L would receive the same punishment due to a later regulatory document) but positive; the same punishment for refusal to take a breathalyzer test; and up to 3 years of jail time and license cancellation if over 0.3 mg/L. Analysis was done using decision tree analysis as well as game theory to evaluate the rational choice for drunk drivers according to possible financial loss.

RESULTS: The authors have found that the rational choice for a drunk driver is not taking the breathalyzer test to avoid heavier penalties. This, in turn, contributes to the inefficacy of the law.

CONCLUSION: The authors have also calculated that the fine for refusing should be around 2.5 times higher so that the economic equilibrium would shift toward encouraging drivers to take the test. This should also be accompanied by other incentives to promote safe behavior while driving.