Road transport accounts for the majority of CO2 emissions within the transport sector in the European Union, yet most research has focused on optimizing routes and reducing emissions in urban logistics, with little attention given to long-distance passenger travel. This study examines CO2 emissions from interurban bus routes and explores ways to improve sustainability without reducing service efficiency. Using the Granada-Cartagena route in Spain as a case study, the analysis highlights the direct impact of stop frequency on emissions. Findings suggest that excessive stops not only increase fuel consumption but also prolong travel time, reducing the overall efficiency of the service. A digital system based on passenger demand could adjust stops in real time, ensuring buses stop only where needed while maintaining accessibility. Therefore, interurban buses should be included in sustainable mobility plans to help reduce emissions.