When we didn't know any better (silly Westerners), my daughters and I stopped for a steering wheel sized turtle, put her in the back end, took her to the nature center, where they said turn right back around and put her back. She's laying eggs in the sand by the edge of the road. Put her back in the back of the car and there were a bunch of what looked like ping-pong balls, she laid whilst riding around. They told us she was big enough to bite off a finger, but we knew turtles and had no trouble with her. We buried the eggs she left in the car, but nothing came of them.

I would have tried to contain it, first, then called a nature center.