The advent of driverless vehicles, including automobiles and buses, may considerably affect the competitiveness and ridership of public transportation services in negative as well as positive ways. Since driverless vehicles may be widely used in the fairly near future, public transit operators and transportation planners should prepare to deal with their anticipated effects. In this thesis the author (1) formulate modular optimization models for both human-driven and automated bus services with fixed routes as well as flexible routes, (2) develop preliminary quantitative assessments of those effects, showing that without drivers, competitiveness of public transportation compared to private transportation decreases; (3) conduct sensitivity analyses to explore how changes in input parameters affect the results; and (4) identify insights in which transit operators, transportation planners and other transportation system stakeholders may use in effectively adapting to the introduction of driverless vehicles.