Psychological interventions for environmental impact: A field experiment on reducing engine idling

A large-scale field experiment (N = 8948) tested psychological interventions to reduce engine idling at short-wait stops. Persuasive messages based on social influence, informational influence, and identity-based influence/community engagement were displayed at a busy intersection. This study extends previous research by (1) considering shorter waiting times (i.e., red light stops) and (2) investigating the effect of messaging over longer time periods, including post-intervention. Compared to pre-intervention baseline, all messages significantly reduced idling rates in the first phase of the experiment, by 6–16 %. The effect was retained two weeks after signs were removed. In the second phase of the experiment, the most effective message (informational influence) was displayed again over four weeks, revealing a sustained effect on engine idling reduction that persisted one week after the sign was removed. This field experiment supports the efficacy of theory-driven messaging interventions to trigger sustained pro-environmental behavioral changes. Future studies may investigate the generalizability of the present findings to other settings. We highlight implications for psychology-based pro-environmental interventions.