• Few works tested normative messages to nudge people toward sustainable mobility. • Descriptive and injunctive norms with info on a green alternative were employed. • Statistical tests analyzed the effect of norm messages on travel behavior change. • Injunctive messages show positive impact on the intentions to use public transport. • Varying effectiveness is found depending on trip and socioeconomic characteristics. Urban communities' travel behavior is one of the key factors in implementing behavioral interventions to promote sustainable mobility. This study investigates whether receiving a normative message alongside feedback information (on time and cost savings, reduced emissions, and burned calories) can contribute to persuading individuals toward sustainable mobility. For this purpose, we conducted a randomized controlled trial experiment in 2021 in the metropolitan area of Cagliari. We intercepted a sample of students and workers who usually commute by car and proposed them a personalized sustainable alternative (walking, cycling, or public transport). Then, we contacted participants again asking about their intention to use the proposed alternative, after presenting them with one of five randomly assigned normative messages: descriptive, injunctive, descriptive+injunctive, injunctive+descriptive, and no message (control group). For our analysis, 577 responses to the last survey were considered. Results show that a large share of the sample (36.9%) intended to change travel behavior. Furthermore, we found that the injunctive normative message is significantly more effective for public transport. Instead, no significant differences were detected when an active mobility alternative was proposed. Finally, our analysis revealed different normative measures' effectiveness depending on the trip characteristics of the suggested alternative and the individuals' socio-demographic characteristics. [ABSTRACT FROM AUTHOR]