UC San Diego

This dissertation studies how transportation costs and frictions shape economic activity within and across cities. Across three essays, it examines how commuting costs, transit networks, and trade frictions affect where people live and work, how firms and households connect to markets, and how public policy changes welfare.The first chapter develops a quantitative urban model in which private and public transit jointly determine commuting costs within a city. We investigate how private providers’ decisions shape commuting costs considering complementarities with the public network, and the welfare gains and spatial consequences of policies that directly shift prices such as fare regulation and subsidies. The mechanisms underscore that the endogenous response of the private sector and network-wide cost interactions are central to understand the effects of transit interventions.The second chapter, coauthored with Leticia Juárez and Román Zárate, studies optimal transit networks in developing countries. Combining a spatial model with network and commuting data, it shows how budget-constrained governments should allocate transit infrastructure across public mass transit and privately operated services. The analysis highlights the additional welfare gains from accounting for private network design rather than expanding only public mass transit.The third chapter, coauthored with Alfonso Cebreros and Daniel Ramos-Menchelli, examines domestic trade frictions created by crime. Using confidential data from Mexican transport firms, agricultural markets, and administrative crime records, it measures how crime exposure along shipping routes raises trade costs and affects prices, market access, and welfare. The chapter shows that crime can make locations economically distant even when they are geographically close.Together, the chapters show that transportation costs are not exogenous outcomes purely determined by technological or infrastructure constraints. They are shaped by infrastructure, congestion, network design, and institutional conditions, and they play a central role in determining the spatial organization of economic activity.