Planning for isolation? The role of urban form and function in shaping mobility in Brasília

Abstract

Brasília offers a rare test of how urban form shapes experienced segregation. Built almost at once around modernist neighbourhood units, then expanded through planned satellites and informal peripheries, it lets us ask whether urban form turns mobility into mixing or into a more efficient engine of separation. We combine data on human mobility with urban morphometrics, amenities, road networks, along with enclosures and tessellations that capture segregation at the scales where access is structured: districts, neighbourhoods, blocks, and street-and-building cells. We find that segregation intensifies as resolution sharpens, from 0.282 at the district scale to 0.545 at the block scale, indicating that Brasília looks most integrated at coarse units and most segregated where everyday encounters are actually organised. Mobility softens home segregation for most users, but not symmetrically: poorer groups travel farther, while affluent groups remain the most selectively exposed. civic cores and mid-rise, mixed-use areas are the least segregated morphotypes, yet they occupy only a sliver of the metropolis. Elsewhere, rich lakefront suburbs and dense poor settlements reach similarly high segregation through opposite spatial logics. Amenities predict lower segregation, while barriers and enclosed residential interiors predict higher segregation. Built form explains more of this pattern than visit volume alone in the segregation models: integration is less a property of residential design than of shared destinations and porous connections. Planned capitals can build order without building isolation if they distribute mixing space rather than sequestering it.

Figures (15)

• Figure 1: The structure, form and history of Brasília. Images taken as part of the Corona program in 1972 showing Brasília 17 years after it broke ground: even before the Plano Piloto was finished, construction had already begun on the Guará suburb and the Ceilândia community for those relocated from informal settlements nearer to the centre. Águas Claras, which was not developed until 1992, is vacant in the image. We also show figure-ground images of different zones as they exist today, with a variety of forms spanning towers-in-the-park superquadras, the dense grids of Guará and Ceilândia and the sparse suburbs of Lago Sul and Lago Norte.
• Figure 2: Experienced segregation in Brasília.A Place segregation by tessellation in selected areas. Lago Sul and Lago Norte are segregated almost throughout, while the superquadras and Guará often combine segregated residential cells with more mixed commercial corridors. B Radius of gyration by income quintile. Poorer groups travel farther each day than richer ones, consistent with compelled mobility. C Individual experienced segregation $S_i$ by income quintile. Despite travelling less, the richest quintile remains the most segregated in experience.
• Figure 3: Morphotypes and experienced segregation.A The results of our morphometric classification, which distinguishes between commercial zones in red and various residential communities, including the superquadras within the Plano Piloto in pink, Lago Sul and Lago Norte in yellow, Ceilândia in purple and green. B The matrix of interactions between different morphotypes, showing that mobility concentrates within morphotypes---when trips cross morphotypes, residential areas feature as sources and commercial corridors as sinks. C Place segregation $S_\alpha$ across morphotypes, showing that civic cores---which are present in both the Plano Piloto and Águas Claras---have the lowest place segregation; suburbs typically have higher place segregation.
• Figure 4: Who interacts with whom and where.A Mixing matrices for select morphotypes show the probability that a user from income group $i$ shares a cell and time window with a user from group $j$. The diagonals mark assortativity: across all morphotypes, within-class encounter is more likely than between-class encounter, but the composition of that assortativity varies sharply across urban forms. B Individual experienced segregation $S_i$, grouped by home morphotype. Mobility usually reduces segregation relative to the home cell, but the extent of that reduction varies by residential setting. C Spatial correlograms for place segregation $S_\alpha$ and resident experienced segregation $S_i$. Nearby places resemble one another more strongly than nearby residents do. D Visitor income distributions for contiguous civic-core clusters. Similar centralities attract different publics depending on their position in the metropolitan system.
• Figure 5: Modelling the role of form, function and demography.A Residuals from our model of place segregation $S_{\alpha}$ in selected areas. Positive residuals mark cells that are more segregated than predicted by their local built form and demographic context, while negative residuals mark cells that are more mixed than expected. The lakefront suburbs remain more segregated than the model predicts, whereas several corridor-like and mixed-use areas are less segregated than expected. B Standardised coefficients from the model, with positive coefficients indicating features associated with more segregation, vice versa for negative coefficients. Amenities are associated with lower segregation, while coverage ratio and greener contextual settings are associated with higher segregation, indicating that both dense fabrics and sparse vegetated enclaves can produce separation through different spatial logics. C Comparing the share of all mixed interactions, when a person of one quintile shares the same tessellation at the same time as someone from a different quintile, to place segregation $S_\alpha$, by morphotype: civic cores comprise a plurality of these mixed interactions, but other typologies account for more visits, represented by marker size.