Out of the box, the AI driving ability is too perfect, I very rarely see any kind of accident unless I cause it myself. So, I changed their ability to react and made it a little more human. Now, you can stand at an intersection and wait for a few seconds and distracted drivers, tailgaters, speeders, etc., will make their commutes more interesting. The sports cars drive too aggressive the trucks can't brake fast enough, the crappy cars go too fast, and the motorcycles are just funny. For real pile up fun, stand on an overpass and after a minute or two someone will make a mistake and all hell will break loose.