From Bangalore to the Bay Area: Comparing transportation and activity accessibility as drivers of urban growth

What determines urban growth and how do these factors vary globally? An understanding of the factors that drive urban spatial form will be critical for urban—and ultimately environmental—sustainability. We hypothesize that easy access to economic or social activity is a primary driver of urban form. From this, a city's spatial form is largely determined by the time–cost of access to transportation and activities. We use a stochastic pixel-based model to test the hypothesis of accessibility-driven urban growth using two case studies: Silicon Valley, U.S., and Bangalore, India. This study is the first to develop a spatially explicit modeling approach to urban growth in a comparative framework spanning the developed and developing world. Our analysis shows that Silicon Valley's relatively inexpensive auto-based transport (in time and financial costs), dispersed employment locations, and high labor force participation rates have resulted in intermittent and expansive highway-oriented urban growth patterns. In contrast, Bangalore's expensive non-auto transport (in time and financial costs), low participation in the formal economy, and emphasis on informal economic activity has produced a tighter clustering of urban development near existing urban locations. Over time, generally decreasing transport costs in both locations have led to increased dispersion of urban development. Economic growth in India and the inflows of IT-related foreign investment in Bangalore may further create urban forms increasingly similar to those found in the Silicon Valley. The results have important implications for the development of policies that may lead to more sustainable forms of urban development.