Public transportation is a critical component of urban communities and plays an important role in facilitating mobility which is integral to economic development and the quality of life of urban residents. In recent years, urban transportation has evolved rapidly with the emergence of transportation network companies (TNCs) and e-commerce that drastically transformed urban living. The availability of TNCs has given consumers more transportation options. However, the implications of TNCs on public transit ridership are unknown. In addition, the rising online shopping trend has drastically reduced the businesses of brick-and-mortar retailers, but does the shift in consumer shopping behavior reduce the demand for public transit? The objective of this dissertation is to address the following three research questions: (1) How is U.S. public transit ridership impacted by the rise of TNCs? (2) How have transit subcontracting (or purchased transportation) and TNC partnership affected transit productivity in recent years? (3) Has increased online shopping reduced the demand for public transit service? The key findings of my study are: (1) transit effectiveness of both bus and rail transits declined over the study period; (2) TNC availability increased rail transit ridership in 2015; (3) transit effectiveness was highly significant for public transit, and when examining its effect year-by-year, rail transit effectiveness trumped TNC availability; (4) TNCs are neither a complement nor a substitute of bus transit; (5) for bus transit agencies, outsourcing or purchased transportation is associated with negative efficiency and productivity changes; (6) although purchased transportation has a positive effect on technological change for bus transit, the effect is not significant; (7) TNC partnerships also have a negative effect on efficiency and productivity changes in bus transit; (8) there is a positive significant relationship between shopping mall visits and public transit use; (9) however, the effect of mall visits on transit use is small relative to the effects of car ownership; (10) taken together, the marginal effect of car ownership is 9 times larger than the effect of mall visits on transit use.