Internet of Things (IoT)-based public transportation systems face distinct challenges within the broader realm of IoT. Developers of such systems encounter a notably intricate development environment compared to general IoT systems, which are inherently characterized by elevated levels of complexity and heterogeneity. As successfully applied in other domains, domain-specific modeling languages (DSMLs) can also be employed to facilitate the development of IoT-based public transportation systems and address the challenges mentioned. Hence, in this study, a novel model-driven engineering (MDE) methodology is presented, comprising the steps of using a DSML, called DSML4PT, for the development of a wide-range of IoT-based public transportation applications. Moreover, the usability evaluation of DSML4PT within this MDE methodology during the real applications of IoT-based public transportation systems is also provided, which is missing in similar studies. For this purpose, we investigated the usability of DSML4PT within a systematic evaluation approach in which the features of DSML4PT are assessed both quantitatively and qualitatively in eight different real public transportation applications with the participation of experienced developers. Comparative analysis revealed that approximately 80% of IoT-based public transportation systems could be automatically generated through modeling exclusively employing DSML4PT. In contrast to the conventional software development methodologies, the novel DSML4PT approach also decreased the time required for the development of public transportation applications by almost 50%. In addition, according to a questionnaire-based assessment, the general evaluation rating of the language was measured as 4.44 over 5-point Likert scale. Feedback from the developers corroborated the practicality of this language and its widespread adoption across diverse perspectives.