What is the impact on intra-national trade and regional economic outcomes when the quality and lane-capacity of an existing paved road network is expanded significantly? We investigate this question for the case of Turkey, which undertook a large-scale public investment in roads during the...

The Inca Empire was the last of a long series of highly developed cultures in pre-colonial South America. It stretched across parts of the current territories of Argentina, Bolivia, Chile, Colombia, Ecuador and the whole of Peru. The Inca Road was its 30,000-kilometer-long transportation system....

We use anonymized and aggregated data from Facebook to explore the spatial structure of social networks in the New York metro area. We highlight the importance of transportation infrastructure in shaping urban social networks by showingthat travel time and travel costs are substantially stronger...

We develop a general equilibrium geographic framework to characterize the welfare effect of transportation infrastructure investments. We tackle three distinct but conflating challenges: First, we offer an analytical characterization of the routing problem and, in particular, how infrastructure...

I study the impact of transportation on health in the rural US, 1820-1847. Measuring health by average stature, I find that greater transportation linkage, as measured by market access, in a cohort's county-year of birth had an adverse impact on its health. A one-standard deviation increase in...

Previous work on transportation investments has focused on average impacts in high- and middle-income countries. We estimate average and heterogeneous effects in a poor continent, Africa, using roads and cities data spanning 50 years in 39 countries. Using changes in market access due to distant...

How large are the benefits of transportation infrastructure projects, and what explains these benefits? To shed new light on these questions, this paper uses archival data from colonial India to investigate the impact of India's vast railroad network. Guided by four predictions from a general...

The importance of increments to an existing highway system depends upon their contributions to the accessibility provided by the existing network. Nearly 40 years ago, Mohring [1965] suggested this logic for planning optimal highway investment programs. He argued it could be implemented by...

During the 1850s, land in U.S. farms surged by more than 100 million acres while almost 50 million acres of land were transformed from their raw, natural state into productive farmland. The time and expense of transforming this land into a productive resource represented a significant fraction...

In this paper, we examine the effect of changes in population density--urban sprawl--between 1970 and 2000 on BMI and obesity of residents in metropolitan areas in the US. We address the possible endogeneity of population density by using a two-step instrumental variables approach. We exploit...