In 2016, the transportation sector became the single largest emitter of carbon dioxide in the US, emitting almost 2 billion metric tons of carbon dioxide per year. American cities and their metropolitan areas contributed about 63% of total transport emissions and have been responsible for 80% of the increase in transport emissions in the last decade. Less dense urban areas tended to have higher per-capita CO2 emissions. However, growth in transport related CO2 emissions has occurred in almost every US city, even those that are relatively dense and have lower car dependence per capita. This thesis investigates the impact of jobs and population on the transportation emissions in the six county Chicago region. The Chicago area has been an outlier among its peer cities in terms of transport based emissions since 1990. Cities with similar densities either lowered their transport emissions or exhibited no change between 1990 and 2010, while Chicago’s population density declined and its transport emissions increased. This study attempts to gain insights into the reasons for the higher transportation emissions.

This analysis uses the DARTE, Census and Census’ LEHD databases to analyze population, job and transport based emissions in the Chicago region from 2005-17. Data analysis indicates that simultaneous job centralization as well as decentralization is occurring in the region along sustained loss of population in Cook County and a trend toward suburbanization. Two additive models were created to conduct regressions. One used jobs, and population as independent or explanatory variables, and transport-related emissions (TREs) as the dependent or response variable. In the second model, job density and population density were the independent variables and per capita TREs were the dependent variable. Regressions were also conducted for inflow and outflow data of commuting workers and distance traveled to work against transport related emissions data.

Jobs were found to have statistically significant positive correlations with transport related emissions for the overall region while population had negative correlations. Within Cook County, this relationship was only evident after 2010 while for the five other counties there was only a statistically significant positive correlation between jobs and transport based emissions. Inflow and outflow of workers had a positive correlation with transport based emissions especially in the outer suburban counties of Will, Kane and McHenry counties and is a good proxy for transport related emissions in the five outer suburban counties. Policy recommendations include expanding transit service, especially adding inter-suburban connections, encouraging employment and residential transit oriented development, and implementing congestion pricing in Chicago’s central business district (CBD).