Within the framework of studies on accessibility, this article proposes to address the conditions offered by public transportation —understood as a structure of opportunities that provides access to urban goods and services—, taking the Greater Buenos Aires as spatial universe. Based on a Google tool that collects data from the public transport network in its multiple modes, an indicator is constructed (travel time to the city center) which allows working on a metropolitan scale and, at the same time, provide an account of the microspatial differentials configured within it, in a cross talk with urban expansion processes and the patterns of socio-economic spatial distribution. Thus, it is observed that the unequal way in which public transp...