The street network of a city is a dynamic entity in continuous change. Sometimes change can be seen as 'permanent', sometimes as 'temporary.' New streets or changes to existing streets can be seen as permanent. Signal malfunctions, potholes, accidents change the capacity of the network can be seen as a temporary change. The dynamic nature of the network requires a tool to model and analyse it; while allowing constants updates. This work proposes a Petri net tool that allows the user to flexibly model, modify and analyze in a progressive fashion a street network. An example of its use is included. The work is restricted to the definition of the network.