The article presents an approach to the development of a case-based decision support system for assessing the safety of a section of a city's transport system. To store the database of precedents, it is proposed to use an OWL ontology. The use of the ontological approach allows a more accurate interpretation of the subject area, and over time will expand and supplement information about the precedent. The precedent structure is defined. The ontology architecture is given: classes, properties and instances. An example of filling the ontology with precedents is given, using the example of the city of Volgograd. Measure of proximity to compare precedents is proposed. The procedure for adding new precedents to the knowledge base is considered. With the help of the developed decision support system, it is possible to assess the safety of both individual road sections and the entire transport infrastructure of the city.

Keywords: ontology, reasoning by precedents, transport, transport security