Surveillance sensors represent the various means used to extract data on traffic flows in the network. Sensors in MITSIM are represented by their technical capabilities rather than by simulating their operations in detail. For example, a measurement error is assumed instead of being derived by the physics that govern the operations of a sensor. When a vehicle passes a detector the occupancy and speed are interpolated based on its previous and current positions over the update phase (e.g. 0.1 second), assuming constant acceleration.
Sensors of the same type at the same longitudinal position in a segment are grouped into a sensor station. Each sensor station is characterized by sensor type, sensor task (i.e. the types of data collected by the sensor), length of detection zone, longitudinal position, and the detectors it consists of (only a subset of the lanes may be equipped). In addition, each sensor is assigned a working probability, which specifies the probability that the sensor is operational. The measurement errors for various types of sensors and data items are determined by parameters of the surveillance system module in TMS.
Simulation of other surveillance methods, such as external agency reports, is also possible in MITSIM. For example, when passing an incident, vehicles equipped with a cellular phone will report the incident to the traffic management simulator with a pre-specified probability.