In Rio de Janeiro, immobility or the share of people with no journeys on any given day is very high (46%). Immobility has a marked geographical dimension in what is a segregated city. But income has only limited explanatory power. The population structure, with high proportions of people who are not in the labour force and who are unemployed, accounts for the high levels of immobility in the poor districts. Although population structure effects prevail, spatial factors such as the severance effect also account for differences between districts. Indeed, Rio de Janeiro features many different types of barriers that affect immobility in several districts and for several population groups. These barriers may be physical or symbolic and perceptive. This study proposes therefore to identify the scope of those barriers as they affect immobility. Our findings from the latest household travel survey available for the metropolitan area of Rio de Janeiro (2003) illustrate the effects of the two types of barrier, physical or symbolic and perceptive, on immobility that more specifically mark out certain categories of individuals such as housewives, the elderly, the unemployed or poor workers. Conversely, the wealthier active population seems to be little affected by the two types of barriers under study. Lastly, our results show that social fragmentation does not lead to greater immobility of favela populations in the heart of rich districts, but on the contrary to increased mobility, especially for the working age population in employment or looking for employment.