As a significant contributor to city greenhouse gas emissions, transportation also holds significant potential for decarbonising Europe. However, data-driven sustainable mobility planning for cities is a challenge due to the difficulties in transport data collection. This is where Google’s Environmental Insights Explorer (EIE) can help. As shown in this case study by the cities of Braga, Stockholm, Tampere, Vitoria-Gasteiz and Warsaw, EIE can play a valuable role in the mobility plans of municipalities by providing granular data on modal share and transport emissions across a range of boundaries within the city, thereby supporting planning and impact monitoring of actions over time.