Environmental Impacts of Shared Mobility: Potential, Factors, and Assessments

Sammanfattning: Environmental impacts from passenger transportation continue to increase globally due to a rise in kilometers traveled and a shift to emission-intensive transportation modes (from public transportation and active modes such as walking and cycling to motorcycle and car ridership). The electrification of the passenger fleet, coupled with low-carbon energy sources, is expected to decrease some of the environmental impacts associated with passenger transportation, including local air pollution, greenhouse gas emissions and fuel depletion. However, different environmental impacts might increase due to this shift, including rare metal depletion and increased pressure on the already-overloaded electrical grid in some parts of the world. Moreover, this shift does not address the increase in transportation activity and the shift to more emission-intensive transportation modes. Shared mobility is a demand-side mechanism that has the potential to change travel behavior and vehicle ownership rates among users. This dissertation aims to understand the potential of shared mobility to decrease the environmental impacts of passenger transportation and to understand the factors that might affect this potential. Here I focus on car sharing, with additional attention to ridesharing, bikesharing, and scooter and moped sharing. In this research I design and apply assessments using life-cycle analysis and multiregional input and output analysis to evaluate the environmental potential of shared mobility. My findings add to our knowledge and understanding of the potential of shared mobility. This study also adds to environmental assessments methods by applying multiregional input and output analysis in a novel way.Changes in both travel behavior and expenditures influenced the impacts of car sharing. Greenhouse gas (GHG) emissions from passenger transportation may either decrease or increase after people engage in car sharing. People who give up private vehicle ownership and shift to active, public and shared transportation decrease their emissions, while people who increase their solo driving increase them. Changes in travel behavior affect the way people spend their income: for example, decreasing spending on fuel, insurance and maintenance while increasing consumption of other products and services. These changes in spending are related to rebound effects that have the potential to decrease reductions in GHG due to car sharing by 71-80%. The potential of car sharing to decrease the environmental impacts of passenger transportation is also affected by how it was designed and implemented. Differences in ownership models—i.e., whether shared cars are owned by a company or individuals—are found to have a limited influence on GHG emissions. The specific context of a car sharing system will determine the best form of implementation and its transformational potential. Contextual factors include variables such as the robustness of public transportation networks, cyclist and pedestrian safety, and the availability of charging infrastructure. Car sharing can be 14 a tool to drive a shift away from car ownership; however, countries that have a higher share of public and active transportation users are more likely to witness a shift away from car ownership with the incorporation of car sharing than countries that have high rates of car ownership and use. This study suggests that shared mobility does not, by default, lead to a decrease in the environmental impacts from passenger transportation. It instead suggests that shared mobility needs to be designed, implemented and used in a certain way in order to achieve this goal. Shared mobility might be implemented in several contexts as one of several tools to reduce environmental impacts from passenger transportation, and in this work I find that a combination of several tools has the greatest potential to achieve such a reduction.