When Nudges Aren't Enough: Incentives and Habit Formation in Public Transport Usage

In three large-scale field experiments with over 32,500 individuals, we investigate whether public transport uptake can be influenced by behavioral interventions and by economic incentives. Despite their effectiveness in other domains, we find a tightly estimated zero for social norms and implementation intentions on ridership. Increasing the economic incentive significantly increases uptake and long-term usage. This increase is sustained for months after removing the incentive. The effect is mainly driven by initial low users, which is evidence for habit formation and highlights the heterogeneous effects of the policy. While there is scope for long-term behavior change, nudging might not be the right approach.