In October 2011, Atlanta, Georgia, opened its first high-occupancy toll (HOT) lanes, which were converted from high-occupancy vehicle (IIOV) lanes. In partnership with the Georgia Department of Transportation, the Georgia Institute of Technology established a research team to assess changes in vehicle throughput, vehicle occupancy, and passenger throughput associated with the 1-85 HOV-to-HOT lane conversion. For the assessment of these measures, commuter bus ridership, which carries a significant portion of ridership, could not be collected through the applied efforts to collect field data. Moreover, the effects of ridership and vehicle throughput on vanpools, which also use the managed lanes, are unknown. The purpose of this research was to estimate the change in vehicle and person throughput of alternative modes before and after the HOV-to-HOT lane conversion. The results indicate that person throughput remained relatively stable for commuter buses, even with an increase in vehicle throughput. The vehicle throughput of vanpools was not substantial and increased slightly after the conversion. The commuter bus results were unexpected, as ridership was expected to increase because of the related (ravel time saving and reliability. Behavioral research is needed to understand the underlying effects of ridership to separate the underlying effects from external factors such as gas prices, travel times, employment, and others.