For this report data is collected from almost 2,300 miles of the California's most heavilytraveled urban freeways. There are two methodologies for collecting HICOMP data. The most frequently used method resorts to probe vehicles to sample traffic conditions on 'typical' days. The other method is to collect traffic measurements directly from fixed traffic detectors. In 2001, Caltrans Districts 3, 4, 5, 6, 10, and 12 only used probe vehicles, District 7 only used loop detectors, and Districts 8 and 11 used a combination ofboth methods.
