Simulation-based planning by emergency management agencies for region-scale evacuation scenarios requires fast execution of large vehicular traffic models. The planning problem is behaviors of population as well as the far-reaching dependencies inherent in heavily stressed network conditions spanning wide spatial scales. Parallel execution is, thus, required to sustain the required detail, size and speed. However, few parallel simulators exist for such applications, partly due to the challenges underlying their development. While most existing simulators are limited in size to a few hundred thousand road segment intersections, region-scale scenarios can involve millions of intersections. Moreover, many simulators are based on time-stepped models, which can be computationally inefficient for the purposes of modeling evacuation traffic. We are addressing the speed and scalability problems using a two-fold approach.