Alternatively with the civilians, you can do
this setbehaviour "careless" and they won't care if they see OPFOR, but a side-effect of this is they aren't scared by gunfire, either :/
If you don't want anyone in the front seats, they are automatically used first by the AI AFAIK. You can drop a gamelogic or two (depending on the amount of front passenger seats) down and write
this moveincargo truck1 n their init fields. Then you will get in the back when you do the ordinary get in action