Traffic simulator

Without going into too much detail my task is to develop a simulation of the operation of a set of traffic lights at a crossroads or a T-junction. Vehicles arrive at random and wait until they are at the front of the queue and the light is green, when they pass across the junction. There are a few specifics which need to be taken into consideration. However im not sure where i should start.. could someone help me design the system, or give me hint to some of the classes ill need to include (im pretty clueless).

Any input would be appreciated,
Ash.

Try to start with threads. Just read a documentation, and I think it is the best solution for this. Looping is too bad in such instances, because we don't know how long it should run.