In the field of road safety, many solutions have been developed for monitoring public transport vehicles. However, the vast majority of technological solutions is focused on solving the problem of information availability to users; only a few seek to solve the problems leading to traffic accidents involving such vehicles. In addition, proposed solutions are not based on standards such as the Intelligent Transport Systems (ITS) architecture, which eases development and integration with other mobility services. To encourage new developments in this area, we developed a proof of concept for checking the viability of a public transport vehicle tracking service, through a pilot project in an intermediate city in Colombia. We used a specific ITS architecture for designing the service, based on ARC-IT (current American ITS architecture), adapted to the city's context. Then, we developed the service through an IoT platform implementation methodology. Finally, we tested the service through a pilot deployment. This article presents the features of the developed service and the pilot's results. We conclude that the use of the ITS architecture and a platform design methodology facilitates an organized, structured process for developing mobility services in a city.