Introduction Several plans have been announced recently to reduce emissions, with a focus on climate change. Current methods for creating attractive and sustainable transport take a broader perspective, including transport-related emissions and noise, but lack general guidance on public transport across national and regional borders. To fill this gap, the authors developed a strategic planning model for sustainable mobility.Methods Research activities were mainly carried out within the South Baltic Sea Region project Interconnect, whose purpose was to curb car-reliance by increasing public transport across national and regional borders. The study drew on experiences from earlier and related studies, literature reviews, stakeholder collaboration workshops, a survey, and expert interviews.Results and Discussions This resulted in a process model that embeds the Framework for Strategic Sustainable Development, including its Sustainability Principles, and a procedure for planning towards sustainability that, when applied, can lead to a plan for sustainable public transport across national and regional borders.