The Praxitele project is responsible for the design of a new kind of transportation in an urban environment, which consists of a fleet of electric public cars. These public cars are capable of autonomous motion on given journeys between stations. The realization of such a project requires experimentations with the behaviour of autonomous vehicles in the urban environment. Because of the danger connected with these kinds of experiments in a real site, it was necessary to design a virtual urban environment in which simulations could be done.Animations or simulations in Virtual Urban Environments can be performed in various ways, but one common element of such systems is that they require a model of the environment. Reproducing the real traffic of a city, as completely as possible, implies the simulation of autonomous entities like living beings. Such entities are able to perceive their environment, to communicate with other creatures and to execute some actions either on themselves or on their environment. Interactions between an object and its environment are, most of the time, very simple: sensors and actuators are reduced to minimal capabilities which permit only to avoid obstacles in a 2D or 3D world. This is due to the fact that databases for virtual environments are often confined to the geometric level, when they must also contain physical, topological and semantic information. Accordingly, in this paper we propose a model which is designed to connect different levels of representation, by assembling geometric, topological and semantic data in the field of traffic simulation, and its implementation in VUEMS, a Modeling System of Urban Road Network. From real world data (when available), we construct a Model of the Virtual Urban Environment, integrating all the information needed to describe the realistic behavior of car drivers and pedestrians.