While social segregation is often assessed in terms of one socio-geographic space, usually place of residence, more recent approaches also incorporate activity-based and, in particular, mobility-based data. This study extends the use of mobility data to measure social segregation between multiple groups by developing a method to connect socio-economic data from the place of residence to mobility data. The method gets applied on the public transport smart card data of Stockholm County, Sweden, using the ordinal information theory index. Applying the index on the destination mix of 2017-2020 smart card data sets for week 5, shows significant differences between income groups' segregation along the radial public transport corridor. The findings also enable to assess the evolution of segregation. In Stockholm, the overall slight decrease in income segregation can be linked to declining segregation in the city center and its public transport hubs. Increasing zonal segregation is related to suburban and rural zones with commuter train stations. This method helps to quantify and thus better understand segregation based on the dynamics of social life. It also allows an evaluation of public transport, which should facilitate potential interaction between social groups.

While social segregation is often assessed using static data concerning residential areas, the extent to which people with diverse background travel to the same destinations may offer an additional perspective on the extent of urban segregation. This study further contributes to the measurement of activity-based social segregation between multiple groups using public transport smart card data. In particular, social segregation is quantified using the ordinal information theory index to measure the income group mix at public transport journey destination zones. The method is applied to the public transport smart card data of Stockholm County, Sweden. Applying the index on 2017–2020 data sets for a selected week, shows significant differences between income groups’ segregation along the radial public transport corridors following the opening of a major rail project in the summer of 2017. The overall slight decrease in segregation over the years can be linked to declining segregation in the city center as a travel destination and its public transport hubs. Increasing zonal segregation is observed in suburban and rural zones with commuter train stations. This method helps to quantify social segregation, enriching the analysis of urban segregation and can aid in evaluating policies based on the dynamics of social life.@en