Ghost Mode is a feature on TruckersMP that prevents accidents when spawning in to areas that are not NCZ (Which we've had in the past before the existence of Ghost Mode. Upon someone spawning in on the middle of the road, if you were unlucky enough you would be caught in the middle of their truck, or you would slam into the back of their trailer). It will be enabled for 10 seconds, more than enough time for other players to be notified of your presence, and more than enough time for you to start your truck and move out of the way.
If you spawn inside of another truck in a parking lot that doesn't have NCZ enabled, you should quickly pull away to avoid a collision.
You are visible to other players when you have Ghost Mode enabled, you can see other players when you have it enabled, and both of you will be protected against collisions if either of you have it enabled. It works vice versa.