PLAN 80: Article
Honing The Accuracy Of Urban Planning

New Open-Source Software Helps Predict Impacts of Policy Decisions

Researchers in SA+P's City Form Research Group have created a new set of tools that offers architects and urban planners a better understanding of how the spatial patterns of cities affect the way people live and move around their urban environments. The first of its kind to be made available for free, the Urban Network Analysis (UNA) toolbox comes as an open-source plugin for the ArcGIS mapping software.

With 50% of the world's population now living in cities, and another two billion people expected to move to urban areas in the next twenty years, the pressures of rapid urbanization often mean that careful urban planning is difficult, and may be completely overlooked in ad-hoc situations like informal settlements, where 30% of urban populations currently live. In part because of that, 70% of today's urban growth occurs without the benefit of formal planning processes; if that situation doesn't change, the inefficiencies of contemporary cities may become the norm in the future. The UN estimates that China will need to build new cities for 350 million people in the next 20 years. Over the same period, 250 million new urban dwellers are expected in India and 380 million in Africa.

Making use of mathematical network analysis methods, often used to study social networks like Facebook, the UNA toolbox examines urban issues like accessibility, spatial patterns and urban growth to offer policymakers a detailed look at how their decisions would shape nearly every aspect of urban development, including such considerations as where traffic is likely to be highest and on which streets local commerce is most likely to flourish.

Specifically, the software lets planners study urban areas by analyzing aspects of location. For example, it's possible to measure a location's 'reach' (how many locations, jobs or residences are accessible when traveling by the available street network) or 'betweenness' (a measure that can be used to gauge the amount of traffic an area receives). Such an approach could be used, for example, to estimate the impact of a new transit station on a given neighborhood or to help decide what would be the best use for a building.

The tools incorporate three important features that make network analysis particularly suited for this work:

  • they account for geometry and distances in representing the urban environment as graphs, distinguishing shorter links from longer links as part of their computations
  • unlike previous software tools that operate with only nodes and edges, the UNA tools include a third element -- buildings -- which are used as the spatial units of analysis for all measures: two neighboring buildings on the same street can therefore obtain different accessibility results
  • the UNA tools allow buildings to be weighted according to their particular characteristics -- more voluminous, more populated, or otherwise more important buildings can be specified to have a proportionately stronger effect on the analysis outcomes
  • By giving planners more rigorous insight into how a city's configuration affects its quality as a host to human activities, the toolbox can help make future urban planning and design more accurately reflect reality. The tools can also give city designers and planners a better handle on how to improve existing cities based on empirical evidence.

    The development of the UNA toolbox was led by Andres Svetsuk (SMArchS'06; PhD'10, Urban Design and Planning), a lecturer in the Department of Urban Studies and Planning. It can be downloaded here.