An AVM system provides information to a central dispatcher regarding the location and status of vehicles in a fleet. The technologies used for location estimation include radio trilateration techniques, fixed signpost sensors at intersections, and dead-reckoning systems. Each type of technology is characterized by particular location error characteristics, which in turn influence the impact of AVM on operating systems. Probabilistics models for certain location error characteristics are presented for each of the three technologies. A second class of model (characterizing the behavior of dispatchers of emergency service vehicles) is also used to estimate the operational impact of AVM upon dispatching. The advantages of the system include improvements in narrow efficiency measures and its potential as a research tool for conducting deployment experiments in urban service systems. Relevant studies, diagrams, mathematical formulas, and 10 references are included.