Simulating Random Agent Movements along Roads on Map

I need to simulate agent movements on map as follows: Agent starts a known location and moves along a road. At each road intersection, the agent uniformly chooses one possible road and moves along that. The path chosen is to be traced with a poly-line. I know how to choose a path uniformly and mark it with poly-lines once I have the data. But I am looking for how I can retrieve data like road intersection points and the roads leading from there on.