A collection of distributed databases forms an important architectural component of the ATON project for networked incidence management of highway traffic. The database sub-architecture supports the architectural integration of many thematic areas of the ATON, and provides many high level abstractions that semantically correspond to traffic incidents. These databases are queried for the detection of local or distributed traffic incidents by many distributed control and analysis algorithms. The abstract database sub-architecture leads to many concrete databases of different types having different functions. The semantic event/activity database is one of them. The distributed multi-sensory sub-architecture detects atomic semantic events that occur in the environment. The event/activity database stores them and their temporal structures. An activity is a temporal composition of atomic events. A specialized query language is used to flexibly define and detect activities of interest. The query language embodies high-level semantic pattern matching abstractions. Preliminary results of using the event/activity database are also presented in this paper.