This project is in collaboration with a start-up company: Thrivey. The product produced by Thrivey is an automatic tracking application (mobility tracker), also named Thrivey, that can track the movement of the user when they carry their smartphone with them. Furthermore, the future vision of Thrivey is to expand its user group and promote more sustainable mobility activities.Global warming and climate-changing are topics that raise many concerns at all levels in society. Many aspects result in the extreme condition we are facing now. Among them, mobility contributes to significant pollution on the air quality due to the emission of carbon dioxide and other substances, such as SO2. During the COVID-19 pandemic, people’s mobility activities have been reduced significantly. However, how people will travel after the pandemic ends is still unknown. Therefore, it creates an opportunity for this project to investigate how to support people toward more sustainable mobility decisions during and after the pandemic.The main objective of this project is to use self-tracking travel data to support people toward more sustainable mobility decisions.A series of literature research and qualitative user research was carried out. Through the research, the design goal and the final design direction were refined. The design also went through iterations, inspired by insights gathered from user-involved sessions. The final design presented four features that support users toward sustainable mobility decisions. These four features are: personalized advice & indicating restrictions (see chapter 5.3.1), community (see chapter 5.3.2), challenges (see chapter 5.3.3), and informed infographics (see chapter 5.3.4). Through the final design evaluation, the four features were evaluated. The community (with group challenges) feature was found out to be the most motivating feature that can keep the users engaged with the mobility tracking application and hold on to their sustainable mobility goals. Moreover, personalized advice was found out to be the most supportive feature that enables and guides users to travel more sustainably. Additionally, the “indicating restrictions” feature provides a feeling of being understood by the mobility tracker.Furthermore, the informed infographic provides users with insights about their travel behaviour they usually do not aware of. By showing how much restriction the users were facing and what keeps them from travelling more sustainably, users were given a new perspective into their travel behaviour. As a result, this supports, motivates and inspires them to make sustainable mobility decisions.