I think wiqvist’s point was: Though you can create your own “free roam†with cars on the dock prepared to load, and a ferry prepared to accept them, how do you tell them to load?
The answer is simply to trigger the loading when the ferry moors at the dock. The problem is that with logic required to control the cars on the dock, and logic for detecting when the ferry is moored, you are dangerously close to creating an actual mission; that is real scary.
If you want to try making a mission or free roam with cars, you can find instructions in the Mission Editor Notes in the Carz section. It is not difficult to do if you are familiar with the basic operations in the editor. If you have not used the editor, I suggest that you do the exercises in the tutorial section beginning with Getting Started… and continuing through Rescuing a swimmer. That will teach you all the basic moves; how to steer and blow the whistle.
The carz move from point to point. They will go up ramps if you place points carefully at the place where the slope changes. Carz, like other object such as bollards, are initially placed at sea level and must be raised to the surface by adjusting the Y value in their Properties the same way you placed bollards in the exercises.
If you have any questions, post them in this topic or send me a PM. You can also send an email to the address in my Profile. That has the advantage that I may attach example missions to my reply.
I think Carz was the latest section Martin added to the Notes; If your copy does not have Carz, download the latest copy.