18.104.22.168–Process Traffic Probe Data (Pspec*)This process shall be responsible for processing traffic probe data. This process shall calculate vehicle speed per network link based upon the probe data input. The probe data could be obtained from a process that measures the presence of vehicles at locations along the network (e.g. using a vehicle tag), or directly from traffic sensors onboard vehicles that measure vehicle speed and other parameters. The probe data could also be obtained from a fleet of vehicles that are using an automated vehicle location function to track the location of the vehicles (e.g. a transit fleet). Finally, the probe data could be obtained from an analysis of toll transaction records. Based upon probe data inputs received, this process shall calculate the travel time for the links for which probe data has been provided. In the case of direct measurement of vehicle location (e.g. the tag and reader approach) this shall be achieved by noting the successive times at which the tag data is received and calculating the travel time from the difference. The process shall maintain a data store that contains the average travel time for each link in the freeways, surface streets, and rural roadways that is calculated from one of the above forms of probe data. Calculation of the actual average values shall employ some type of aggregation processing (e.g., smoothing or similar technique) and be stored for differing time categories (e.g., times of day, day of week, holidays) in periodic increments. The current delay time for a link shall be the difference between current travel time value and the aggregate processed (e.g., average) value for that time category.
This Pspec is associated with the Traffic Management Subsystem*.
This Pspec is associated with the following Equipment Packages*: