Traffic volume of Roadway Blocks. The dataset contains traffic volume data, created as part of the District of Columbia, Department of Transportation (DDOT) Roads and Highways database. A database provided by the District of Columbia, Department of Transportation identified traffic volume. Count data is collected (both direction) at pre-selected locations on Highway Performance Monitoring System (HPMS) Sections on a three-year cycle. These counts are converted to Annual Average Daily Traffic (AADT).