More realistic driving preferences

One thing that slightly breaks immersion is that trucks will always follow the shortest path available, even if it wouldn't happen as often in real life (for example, driving all the way on the edge of a sheer drop even when there's room available to drive a 'safer' line).
If other factors than just 'shortest' are introduced, this could also be used to give drivers a little bit of personality and make the world feel more organic. (For example, one driver might hate driving on sand, another might like driving through trees, other might prefer a flatter route... etc.)