Two key open source traffic sims. are mentioned: SUMO (traffic sim) and NS2 (network sim). Trans links these 2 simulators together: http://trans.epfl.ch/.
These 2 PDFs will be worth reading: http://www.mobile.ifi.lmu.de/common/Literatur/MNMPub/Publikationen/skso05/PDF-Version/skso05.pdf and http://kom.aau.dk/~evm/dist/Vehicle_Traffic_Microsimulator.pdf
There, needless to say, are commercial versions of sims e.g. http://www.aimsun.com/site/content/section/4/72/. However, if dongles are ever mentioned in a pricing structure, it’s doubtful it’s a good ting … I have a feeling that places like this http://www.trafficware.com/simtraffic7.html won’t be ecstatic about me adapting models also.
An awful lot of the time though, I keep coming back to this link: http://www.traffic-simulation.de/. An email will probably need to be sent. It also has details about the traffic models used, which will be of use.