Urban policy through system modeling: an integrative view of costs and benefits on Commuter Bicycling

This is an review for the “The Societal Costs and Benefits of Commuter Bicycling: Simulating the Effects of Specific Policies Using System Dynamics Modeling” article [1], which was wroten by Alexandra Macmillan, Jennier Connor, Karen Witten, Robin Kearns, David Rees and Allstair Woodward.

Review of the article

This writing is an very interesting article as for how science, through an systems view, can be embraced in an integrative manner to tackle urban policy decision making problems.

In synthesis, the goal and the stated result is to study the economical costs and benefits, in an integrated view, of policies which targets the increase the commuting usage of bicycles on Auckland, New Zealand. This is done through three main tools: the mapping of the causal factors behind bicycle usage through participatory system dynamics modelling, an through review of the available historical data and best guesses for the factors on several sources, and the monetization of the variables associated with each factor through cost estimation and health related losses.

With all of that, simulations for various future policy scenarios are done while fitting the historical data for training and cross-validation. The result is the distribution of how the causal factors are distributed in the near-term future, which in turn can be converted in an financial net-benefit when coupled with the infrastructure costs and monetization of factors.

The comparison between the different policy scenarios provides insights then for what interventions are more effective. Specifically, cycle infrastructure patterns which proceed to transform all roads using best practices perform better than a regional cycle network, for sake of concreteness.

Finally, the article ends with several notes as for how the system model could be improved and adapted for usage in other cities. This is the first active transport article, according to the authors, which uses SDM as an basis for integrating health, social and enviromental outcomes of urban policies, and the methodology as well as the given supplementary materials can be used for replicating and validating this approach to other cities on the world.

An step by step summary for the methodology

  1. Participatory sytem dynamics modelling (SDM)
  2. Use of primary and secondary data for developing a set of qualitative set of feedback loops.
  3. Semistructured intervies by cognitive mapping.
  4. Comparison of the feedback loops from the interviews versus the identified relationshiops on a literature review
  5. Workshops for further refining the preliminary feedback loops
  6. Diagramming through Vensim PLE
  7. Variables and relationships populated with epidemiological evidence, administrative data, and expert opinions
  8. Simulation through STELLA
  9. Simulated scenarios included business as usual and policy scenarios.
  10. Monetization through net benefits vs infrastructure costs
  11. Costs inclued transport estimates, fatal injuries and air pollution factors.
  12. Validation of the model through stakeholder participation and sensitivity testing.


[1] - Macmillan, A., Connor, J., Witten, K., Kearns, R., Rees, D., & Woodward, A. (2014). The societal costs and benefits of commuter bicycling: simulating the effects of specific policies using system dynamics modeling. Environmental health perspectives, 122(4), 335–344. doi:10.1289/ehp.1307250. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3984216/

[2] - https://www.sciencedirect.com/science/article/pii/S2214140516304662