The Geographic Information Systems (GIS) programs offered a multitude of useful analysis tools for a variety of purposes in the transit industry. One of the significant contributions that GIS offers is the ability to manage and spatially display transit data and then overlay these layers to perform analyses. This paper focuses on how GIS can be used in mass transit planning to understand and analyze basic ridership characteristics. Mass transit is gaining a lot importance in recent years because of the growing concern over the impact of automobiles on our environment and specifically on the quality of life in the urban areas. This paper attempted to use GIS to investigate the ridership characteristics of the transit system in Greater London and the D.C. Metropolitan region.<p> In this paper, ridership characteristics essentially refer to the mode of transportation of the working population and their socio-economic characteristics. The ridership characteristics help us understand generalized travel patterns and the preferred mode of transportation; whether the people prefer public transportation to private transportation. My analysis supported the concept that there is often a nexus between the choice in the mode of transportation, and the socioeconomic conditions of the working population. / Master of Urban and Regional Planning