A before and after comparison of vehicle occupancy distributions for the Atlanta, GA I-85 HOV to High Occupancy Toll (HOT) lane conversion scheduled for summer 2011, will assess the changes in vehicle and passenger throughput associated with lane conversion. The field deployment plans and data collection methodologies developed for the HOT evaluation were the result of a comprehensive literature review, an examination of previous data collection methods, an evaluation of the physical characteristics of the I-85 corridor, and the testing of a variety of equipment/manpower strategies. The case study in this thesis evaluates the established vehicle occupancy methodology for consistency across multiple observers during parallel data collection efforts. The differences noted in exact matches and consistency across the use of the "uncertain" values developed for field implementation is specifically assessed. Results from this study are the first step in assessing the validity of the data collection methods used on the HOT corridor and will yield recommendations for improving the methodology for future occupancy studies. A separate assessment of the accuracy of the methodology is also being conducted by the research team and will be published under a separate cover.