Multihreading a single task is not as easy, make task pathing for one vehicle to work in multiple threads is pain. How ever, complex simulation program like this another thing. There are few easyily separated tasks, who could share one data cube. each task could go his own way than send results to the cube. Separated proceses dont need to wait each other or know the status of another task. For example – taks pathing of your vehicles, pathing of people, task simulation grow of cityes, task user interface, and so on so forth. These are pretty independent. Could be programed like separate modules and run in separate threads.