Amsterdam Centrum has been suffering from the spatial competition between overcrowded pedestrian visitors and busy vehicular flows. Application of automated vehicles is a historic opportunity to reclaim the streets for people and change the predicament of the downtown. The thesis focuses on the relationship between walkability and traffic efficiency in Amsterdam Centrum, aiming to maximize the viability and vitality of the city center in the automated era. The whole project, from research to design, is an urban experiment on walkable and efficient-functional city centers. Scenario building is the core approach that has linked research with design. Also, it is a bridge to connect the existing reality with future reality. First, the theoretical study of walkability and traffic efficiency provides the objects for analytical research of Amsterdam. It also helps to select the driving forces for scenario building. Second, theories about viability and vitality provide the evaluation materials for scenario assessment. And the urban design is the continuation of selected scenarios. The key idea of the final design is the movable programme, which means urban functions/human activities can travel in the city like automated vehicles. In the final, the project presents a dynamic urban system and flexible streetscape. It reshapes the relationship between walkability and traffic efficiency by redefining the meaning of city centers and public street with emphasizing on time dimension