Memo: Sustainable Transportation 3.1

Part of a series of “reading memos” that offer a brief summary of interesting academic content along with my personal reflections. This one covers Chapter 2 and 3 of The End of Automobile Dependence by Newman & Kenworthy.


There exists a widely held belief that increasing wealth in a country (measured in GDP per capita) inevitably leads to increasing usage of automobiles for mobility. The authors challenge this notion by investigating a broad slate of statistics in both developed and developing countries. In cities across the United States, Canada, Australia, Europe, and Asia, they present data on private/public transportation infrastructure, public transportation service & use, comparative modal speeds, modal split, transportation energy use and externalities.

The authors find that American cities remain the most dependent on automobiles while European cities have optimized more for biking/walking and Asian cities feature the lowest levels of automobile dependence. Generally, they argue that all the factors taken together are sufficient in painting a picture of declining automobile dependence across the world due to positive developments in urban density, reduced car infrastructure, and stabilizing/declining growth in automobile usage. They argue that “automobile independence” could be declared in a city where 75% or less of total travel is by car, since the character of that city would have changed enough at that point where car-free options would be available for most activities.

With these findings consistent in fast-growing cities such as São Paulo, Prague, and Taipei, the authors demonstrate the viability of Decoupling Theory (the possibility of increasing livability and reducing poverty while reducing environmental impacts). While these developing cities may appear to be choking in traffic congestion on the surface, the authors explain this as “auto saturation” and point to the fact that 70% or more of trips are actually made with public transit as a sign that these cities are not succumbing to automobile dependency.


I was rather impressed with the breadth and comprehensiveness in the set of metrics about transportation patterns that the authors collected. The data reinforced some of the stereotypes I held about cities in these regions (e.g., that Asian cities are rail-centric while American cities are auto-centric), but there were some surprising points about the historical auto dependency of Australian cities and the slowing growth of automobile usage worldwide. Many of the data points were mixed between regions, suggesting that there may be some ingrained cultures around transit/car use that contribute to inertia or momentum in certain directions.

Because of the myriad of mixed signals, I’m not sure I buy the authors’ final argument that we can say automobile dependence is on the decline everywhere – it still feels like too broad a generalization to make. I’m also influenced by recent data showing a surge in car sales in the United States (especially in larger SUVs), though I’m not sure if this is a short-term pandemic-induced spike or sign of a longer-term shift in consumer interest. Among the fast-growing cities discussed that were successful at staving off automobile dependency (São Paulo, Prague, and Taipei), I noticed that heavy investment in high-quality public transit systems was a common factor – likely an essential ingredient for any city hoping to realize the full promise of Decoupling Theory.

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