A global assessment of street-network sprawl

Institute for Transport Studies research seminar with speaker Adam Millard-Ball, Associate Professor, University of California-Santa Cruz

Disconnected urban street networks, which I call “street-network sprawl,” are strongly associated with increased vehicle travel, energy use and CO2 emissions. Moreover, since street layouts are essentially permanent, today’s choices on the connectivity of streets will restrict future resilience and lock in car dependence for a century or more. Using data on all 46 million km of mapped streets worldwide and a satellite-derived time series of urbanization, I present the first systematic and globally commensurable measures of street-network sprawl. Latin America, Japan, South Korea, much of Europe and North Africa stand out for their low levels of street-network sprawl, while the highest levels are found in south-east Asia, the United States and the British Isles. Streets in new developments in 90% of the most populous countries have become less connected since 1975, and the same period saw a near doubling in the frequency of a street-network type typical of gated communities. I also identify persistence in street-network sprawl, indicative of path-dependent processes. Specifically, cities and countries with low connectivity in recent years also had relatively low pre-existing connectivity. The lack of comparative, cross-national analysis has been identified as a major research gap in the literature on urban sprawl, and this assessment provide the foundation for future work to understand urban processes, predict future pathways of transportation energy consumption and emissions, and identify effective policy responses.

Bio: My research bridges urban planning and environmental economics, and addresses some of the key challenges in transportation, energy and climate change policy. My current work examines global patterns of urban sprawl and car ownership, the effectiveness of local climate planning efforts, and the design of carbon trading programs. I also have broad interests in transportation planning and policy, particularly parking management programs to reduce vehicle travel and emissions.
Before coming to UC Santa Cruz, I was an assistant professor in the Department of Geography and McGill School of Environment, McGill University. I hold a PhD in Environment and Resources from Stanford University, and was formerly a Principal with transportation planning firm Nelson\Nygaard Consulting Associates.

Institute for Transport Studies Research Seminar Series: Our seminar series is for anyone interested in the latest transport research. Presented by members of the Institute and guest speakers, the programme is designed to stimulate cross-disciplinary conversations across a range of transport and mobility research areas. The short seminars will be followed by a discussion. The remainder of the session will be a chance to meet up and network. No booking required.