Hey Peter,
In the version that you have, any of the four players can drive the truck and everybody else will get on in the back . From the back of the truck the other players and can shoot and turn around. The new cars all hold a different amount of people including players and NPCs. The game is still in QA, Just finished a new list of bugs and I'm waiting for the next response from them,
I'll let you know when its ready,
Rafi