Latin American cities are challenged by the effects of population growth and insufficient infrastructure. As a consequent, Informal Car Share (ICS) is increasingly filling the gap as a transportation choice for underserved populations. ICS is the use of private vehicles to provide transportation for a fare that is neither taxed nor regulated by any type of government. Although this practice contributes significantly to development and economic growth, it is often stigmatized as unreliable and inconsistent, and little is known about it. This research expands existing definitions of ICS, using cases from Quito, Ecuador, a mountain city located in the Andes region in South America. It does so by analyzing Quito's ICS perceived effectiveness and performance from its users and drivers, the disruptions this system faces in the communities in which it operates, and its resiliency to bounce back from those disruptions. Findings suggested that despite its informality, ICS works with fixed stops, schedules, routes and fares. This is similar to formal systems operated by the government. Users and drivers described ICS as reliable and consistent, and they all reported a positive experience with the service. Findings also suggested that Quito's ICS is disrupted by six natural and political disruptions that delay the ICS service for 10 to 40 minutes. However, ICS proved to be adaptable and able to circumvent disruptions to ensure passengers connectivity to the city. Lastly, findings suggested that ICS users and drivers developed eight adaptation strategies to circumvent disruptions. Those strategies have created a system that aligns with features of resilient urban systems from UN-Habitat. Expanding the current understanding of how ICS operates, as well as its resilience capacity, is the first step to understanding better the value these self-organized systems provide to cities. / Doctor of Philosophy / The population in Latin America's cities is increasing and cities have been unable to keep up with the infrastructure demands that growth has created. As a consequent, Informal Car Share (ICS) are self-organized systems that arose as a solution to fill the gap in the peripheral areas that government provided transportation have not addressed. ICS is the use of private vehicles to provide transportation for a fare that is neither taxed nor regulated by any type of government. Although this practice contributes significantly to development and economic growth, it is often stigmatized as unreliable, inconsistent, and little is known about it. This research explores existing definitions of ICS, using cases from Quito, Ecuador, a mountain city located in the Andes region in South America It does so by analyzing Quito's ICS perceived effectiveness and performance from its users and drivers, the disruptions this system faces in the communities it operates, and its ability to adapt to those disruptions. Findings suggested that despite its informality, users and drivers described ICS as reliable and consistent, and they all reported a positive experience with the service. Findings also suggested that Quito's ICS is disrupted by six natural and political disruptions that delay the ICS service for 10 to 40 minutes. However, ICS proved to be adaptable and able to overcome disruptions to ensure passenger connectivity to the city. Findings suggest that ICS developed eight adaptation strategies that align well with UN-Habitat (2018) characteristics of resilient urban systems. Expanding the understanding of how ICS operates is the first step to understanding the value ICS provide to cities and their urban resilience.