PeMS 6 is the latest of six task orders devoted to research, development, and maintenance of the PeMS system. PeMS collects, processes, stores, and makes available online data from eight Caltrans districts (D3, 4, 5, 6, 7, 8, 11, 12). The data are obtained from 22,067 loops1, grouped into 8,649 vehicle detector stations (VDS). These loops cover 3,154 out of 30,572 directional-miles of interstate and state highways in California. PeMS began as a research project. As the research system evolved, Caltrans determined that the information it provided was very valuable, and additional resources...