Residential and experienced social segregation: the roles of different transport modes, metro extensions, and longitudinal changes in Hong Kong

Social segregation is a challenge intensified by rapid urbanisation. Using mobility data, researchers have widened the scope of analysis from static residential segregation patterns to experienced segregation in activity space. Despite such progress, we have yet to decipher how social segregation evolves with the urban development process. The different roles of transport modes, major transport infrastructure expansion, and longitudinal changes over decades are rarely captured. This study utilises three Hong Kong Travel Characteristics Surveys data from 1992 to 2011 to analyse the city's social mixing changes. Detailed mobility and socio-demographic data of 101,385 (2011), 92,520 (2002) and 77,271 (1992) individuals were included. We found that the unequal experience of social segregation among different social demographic groups has persisted across the two decades. Nevertheless, public transit has a significant effect in increasing social mixing, thereby moderating the experienced social segregation. The roles of buses and the metro system are particularly noteworthy. Nonetheless, we found a selection bias of new metro stations in areas of high social mixing already. Over time, the metro expansion plays a paradoxical role. On one hand, the metro stations' immediate catchment areas have seen a decreased low-income population. On the other hand, the increased number of metro trips allows people to have a more diverse experience.