AbstractOpen Traffic is an open source software project that provides a transport modeling software environment. While most transport model packages offer ready-to-use modules for end-users, Open Traffic provides open access to a modelling environment for the (further) development of methods and algorithms and enables the sharing, distribution and further development of the implied knowledge. The Open Traffic platform is designed as a modular system which enables users to utilize existing modules and extend the system with new ones. The system supports the development of multi modal and multi scale models by providing a collection of objects that enable the creation of a transport infrastructure and its environment at multiple levels of detail. The definition of the geographical objects aligns to the principles of CityGML, an open standard for geo data that is internationally accepted by the Open Geospatial Consortium. Additional utilities such as a graphical editor and visualizer, in addition with facilities to import data from external sources like Open Streetmap and Esri shape files, enable users to quickly create and demonstrate their use-cases. In this article we present the high level architecture of Open Traffic, its current status, and a first application with the implementation of the micro simulation model MOTUS. Also, the possibilities and requirements to adhere Open Traffic to agent based modelling approaches are explored.