Should Self-Driving Cars Be Allowed to Break the Law? Public Acceptance and Tolerance of Discretionary Actions Performed by Self-Driving Cars in Response to Situations Varying by Degree of Acuteness

Many countries are on the verge of introducing highly autonomous self-driving cars (SDCs) into current traffic networks dominated by human-driven vehicles. The complex and dynamic nature of road traffic situations require SDCs to exhibit human-like, discretionary behaviours that may fall outside the scope of formal rules of the road (e.g., straddling solid lines to let an emergency-services vehicle pass). It is important to understand public attitudes towards these behaviours especially when they may lead to negative outcomes. The current paper presents three experiments in which participants’ judgments of blame and trust were probed after being presented with traffic scenarios where SDCs or human drivers decide to perform (Experiment 1 & 2) or not perform (Experiment 3) legal or illegal discretionary actions (DAs) to avoid a danger or optimize traffic flow, with various consequences. The results reveal that SDCs were blamed more and trusted less than human drivers for performing the same illegal DAs. But with legal DAs, this difference was contingent on the acuteness of traffic situations, hinting toward a shift of judgmental focus from the justifiability of an action to the quality of their execution. Additionally, witnessing SDCs performing (or not performing) DAs could potentially improve or worsen their general acceptance depending on the resultant outcome. Our findings paint a promising picture of allowing adaptive behaviours of SDCs; yet highlight the need to establish formal protocols for designing, regulating and appraising DAs of SDCs as well as the necessity of improving the transparency of their decision-making processes to users.