Urban environments, with an ever-increasing population and ever-increasing traffic intensity, today represent a challenge for research and implementation of systems that would improve all aspects of life in such environments. These systems, based on smart technologies, are increasingly present in urban environments. The application of modern information technologies is the basis of these systems, and the application of cloud-based systems, which are key to the integration of systems and data, is particularly important. This paper presents a model of a cloud-based system for air quality monitoring in an urban traffic environment, with the main focus on software services deployed in the cloud. In addition to software services in the cloud, organized in service-oriented architecture (SOA), other relevant parts of the system with which these services communicate are also shown: the sensing layer, local area maps online service, online meteorological service, and a variety of web and mobile user applications. The main feature of the model, which contributes to its application in various environments, is that it is platform-independent, scalable and flexible for possible adaptations depending on proposed requirements.