Smart cities are full of sensors and collect large amounts of data. One reason for doing so is to get real-time information about traffic flows. A next step is to steer the traffic in a way that contributes to the realisation of values such as safety and sustainability. Think of steering cars around schools to improve the safety of children, or of keeping certain areas car-free to improve air quality. Is it legitimate for cities to nudge their citizens to make moral choices when participating in traffic? Would a system that limits a person’s options for the sake of improving quality of life in the city come at the cost of restricting that person’s autonomy? In a transdisciplinary research project, we (i.e., members of the ESDiT programme and the Responsible Sensing Lab) explored how a navigation app that suggests routes based on shared values, would affect users’ experiences of autonomy. We did so by letting people try out speculative prototypes of such an app on a mobile phone and ask them questions about how they experienced different features of the app. During several interviews and a focus group, we gained insights about the conditions under which people find such an app acceptable and about the features that increase or decrease their feeling of autonomy.