Mobility hubs bring together, connect and provide users with several modes of transport. Cities adopt them to help reach several objectives, like the reduction of pollution, congestion and car ownership. As part of the Interreg Mobi-Mix, we have taken a close look at mobility hubs (Interreg 2 Seas, 2020). Based on bibliographic research, discussions with experts and city stakeholders, we established a state of the art that will help to better understand the concept. Cities will benefit from recommendations for a better implementation of mobility hubs. A method of estimating the impact on CO2 emissions at each project step has been developed for two partner cities, Norfolk and Valenciennes. It is mainly based on usage surveys and results from other cities as well as multiplicative factors. The first results point a reduction in CO2 emissions that is greater than the targeted objectives.