There is only one route. Get off ferry, then proceed to the general store on Tankerton Road. Then you have a choice - clockwise or anticlockwise around the island. There are spur roads to explore, but please don’t mix them up with people’s driveways (can be difficult). The general store has maps (or did when I was last there), but you really don’t need them. Once upon a time, there were six settlements on the island, including the prison farm, and they were connected with a sort of ring road. So the roads mostly pass through these. Most of those settlements had names like Esperance or Perseverance and these survive as locations. Some roads were closed when the park was set up, so come to a stop at the fence. Others continue through the park. The distances are not great, and it’s hard to get lost as the bay is almost always visible except where the melaleuca scrub or mangroves are thick. Have fun. Don’t run over any koalas.