From the development of civilization, structure of large settlements have changed in accordance with the needs of the population and the level of scientific and technological development. Due to the COVID-19 pandemic, more smart services have been developed in countries around the world, including Serbia. Based on research and past experiences, the problem of implementing smart traffic and mobility has been identified as a priority with the aim of sustainability. Mutual interactions between different actors will be presented with the aim of understanding cities as structures that must be viewed in the future as smart urban ecosystems that change over time. The research methodology will include case studies and research of opinions of experts in the field of urban planning, mobility and sustainability, and an interview will also be conducted among residents. We propose modern solutions for designing cities as urban ecosystems that can overcome the increasingly negative impacts.