Only processed data is available through the LDS at this time. It can be found in a number of places. Information under congestion is currently incomplete but improvements are scheduled in the next quarter. Caltrans is adding sensors to Bay Area roadways Additionally, sometimes these sensors fail and come back on-line. Yes, active sensors always report data.
Occupancy is determined by the lane used.
The rate at which vehicles pass over the sensors dictates the volume of traffic in that particular lane. The operators have different thresholds that they can select for that aggregation. The operators can also manually enter congestion that comes from the non-automated sources. At this time there are over 8,000 segments. However, this list is subject to change as new segments are defined.