Nudging people to pay their parking fines on time. Evidence from a cluster-randomized field experiment

The timely payment of municipal parking fines signifies people's acceptance of parking regulations, reduces administrative enforcement costs, and prevents additional late-payment fees for individuals. However, public administrations face challenges in enforcing the timely payment of parking fines. A large group of people fail to pay their fines on time, which requires additional enforcement actions that can result in extra late-payment costs and payment-related stress. In this study we collaborate with the Belgian city of Mechelen and the Behavioral Insights Team of the Flemish regional government to test the compounded effects of three communicative nudges. i.e., simplification, explicit penalty, and social norm, on the timely payment of parking fines. In a cluster-randomized field experiment, parking offenders received either the original notification letter, a simplified notification letter, a simplified notification letter accompanied by an explicit reference to the potential penalties, or a simplified notification letter accompanied by an explicit penalty and a social norm message. The results indicate that people can be nudged to pay their fines on time, but only when multiple nudges are combined and used simultaneously.