In this paper, we use secondary data on route level monthly average weekday ridership in the entire Chicago Transit Authority bus system for the Chicago metropolitan area from January 2002 through December 2010, combined with data on gas prices, weather conditions, unemployment rates, population, CTA service factors, and other socioeconomic characteristics of the CTA bus service area, to evaluate the system-wide ridership effects of the CTA Bus Tracker, a real-time bus location technology. The combined longitudinal data source enables us to implement a quasi-experimental design with statistical controls to examine changes in average weekday ridership before and after the Bus Tracker system was implemented on each route.