<p>Children’s and adolescents’ independent mobility without being accompanied by others, such as parents or grandparents, and their use of active modes of transportation, such as walking and cycling, have both declined in recent decades. Awareness campaigns promoting such mobility exist in Switzerland. Yet, reducing affordability barriers to public transport (PT) by means of vouchers to improve independent mobility and reduce car use has not been introduced and evaluated as an intervention. This paper describes a large-scale experiment in the city of Lucerne, embedded within a Real-world Laboratory (RwL). RwLs are a participatory methodology in transformative sustainability research. The provision of PT vouchers was initiated as part of a participatory process anchored in the Children’s Parliament. The Parliament assumed that the introduction of vouchers creates an incentive to use PT. Overall, multivariate statistics indicate higher PT trips in the voucher years. Specifically, count models show significant increases in PT use for school and visiting trips. However, as no corresponding reductions in car, walking, or cycling trips were observed, the findings primarily point to induced demand rather than modal shifts towards PT. From a policy perspective, we conclude that PT vouchers have the potential to contribute to more independent and sustainable mobility opportunities for children and adolescents as part of their mobility socialization.</p>