Two lane road or Interstate? The trip route service at the AAA Club web site would have us take an unknown two lane road from the West Kentucky Parkway to the Park and I guess that would be ok if time was not a factor. In farming country, it's too easy to get behind slow moving traffic on a two lane road. From our home in the western part of Kentucky, we took Interstate 24, Western Kentucky Parkway, William Natcher Parkway, Interstate 65, and State Route 70. The two lane portion was short and in good shape. Speed limits inside the Park get down to 25 MPH. Hard to maintain such a slow speed.
The Green River Ferry runs over the river and leads to Maple Springs and the backcountry area of the park. The ferry trip is maybe a minute long and runs continuously during daylight hours unless its shut down by adverse weather conditions. Its not the most exciting thing in the world, but an interesting sight in a national park. And, the destination of this road, Maple Springs, is a network of trails that allow you to explore the largely unexplored backcountry of this park. There are some shorter hiking options here as well, which make this worthwhile for even a short visit.