Thanks Chris, saves me a job! That's a great photo you posted - a small ferry doing exactly what I envisaged mine doing. I thought I was straying into the realms of whimsy but it proves that there really is
a prototype for everything
Ian, my thinking was led by having to restrict the width of the ferry to 7 inches or so in order for it to turn through a semi-circle on a reasonable width baseboard. I wanted two tracks on deck and the width meant that the wheelhouse got in the way of the port-side track, hence it's single ended. I figured that although with car ferries you want roll-on-roll-off so the vehicles don't need to reverse off, with railway wagons this isn't important as they are themselves inherently double-ended. Fortunately the photo Chris posted bears this out.