PhD Candidate: Emtiaz Hossain Hritan 
Dissertation Title: “Three Essays in Applied Microeconomics”
Abstract: This dissertation consists of three chapters connected by a common theme: examining how environmental and transportation externalities influence public safety and human behavior. Using applied microeconomic techniques, each chapter investigates a distinct yet related outcome—cognitive health, traffic fatalities, and crime. In the first chapter, I investigate the impact of an infrastructure failure on statewide comprehensive exam test scores. The 2007 collapse of the I-35W Mississippi River Bridge in Minneapolis, Minnesota, led to a substantial disruption of the learning environment for students in affected communities. The collapse resulted in numerous fatalities and injuries; notably, a school bus carrying 63 students was on the bridge during the collapse, and traffic patterns were disrupted for a year. Using a two-way fixed effects and synthetic difference-in-differences approach, I find that the bridge collapse leads to lower standardized test scores for affected schools relative to similar unaffected schools. Furthermore, I provide evidence that improvements in air quality due to reduced traffic do not outweigh the trauma-induced psychological stress impacts of the disaster. In the second chapter, I examine the trade-off between safety and noise mitigation by using a quasi-experimental research design to estimate the impact of quiet zone establishment on railway accidents and property values. Railway quiet zones substitute train horns for alternative safety measures at railway crossings to mitigate noise pollution. I find that quiet zones are associated with a 1.27 times higher annual accident rate at railway crossings, which significantly increase fatalities and injuries, while property values near railway crossings increase by 11.07% following quiet zone establishment. A welfare analysis suggests that the housing price capitalization of reduced noise pollution exceeds the safety costs. The third chapter examines the impact of the introduction of ridesharing services like Uber and Lyft on crime rates across U.S. cities, leveraging a natural experiment created by their staggered rollout. Using a Two-way Fixed Effects (TWFE) model, I find that the introduction of ridesharing services leads to a 4.7% reduction in violent crimes, a 5.5% decrease in property crimes, and a 10.4% drop in burglary rates. I also investigate the heterogeneity of these effects across different demographic groups and conclude that the primary mechanism driving the crime reduction is the improvement in employment opportunities provided by ridesharing services.

Committee:
Dylan Brewer (Advisor), Assistant Professor, School of Economics, Georgia Institute of Technology
Casey J. Wichman (Co-Advisor), Associate Professor, School of Economics, Georgia Institute of Technology
Robert Gonzalez, Associate Professor, School of Economics, Georgia Institute of Technology
Daniel Dench, Assistant Professor, School of Economics, Georgia Institute of Technology
Tony Harding, Assistant Professor, School of Public Policy, Georgia Institute of Technology

Date: May 22, 2025 
Time: 10.00 am - 12 pm EST
Location: Old Civil Engineering Building Room 204