Tradable credit schemes to decarbonize commuting trips: Insights from a field trial in a university setting

Source abstract

Tradable Credit Schemes (TCS) are a promising policy instrument for reducing transportation externalities. Their political feasibility may be higher than that of taxes, since policymakers can steer distributional outcomes through the initial allocation of credits, which may in turn increase acceptability. However, TCS require complex decision-making by participants, making empirical evidence on user behavior essential. We conducted a multi-week randomized controlled trial with over 600 participants in a university setting to evaluate the effects of a TCS on commuting emissions. Specifically, we implemented the MobilityCoin system, which prices CO2 emissions. While 18% of the treatment group reported changes in their commuting behavior, compared to 10% in the control group, econometric analysis shows only weak evidence of emission reductions in the full sample. Significant effects are found for specific subgroups, such as public transport users. We find no evidence that participants respond to variation in the price level. Our distance-based allocation leads to progressive outcomes: low-income participants benefit financially on average and do not appear to bear a disproportionate behavioral burden. In terms of acceptability, a majority of treated participants evaluate the system favorably, with more than one-third supporting its implementation at the university. Overall, our results highlight the potential of TCS as a policy instrument: they can induce behavioral change in specific populations while achieving progressive distributional outcomes and relatively high public acceptance.