After I boarded the train, I was walking down the aisle toward the back of the train, looking for a seat. And after crossing into a new car, there was a downslope.
I fell. And I appear to have a mild ankle sprain.
Some of the other folks helped me up and I sat down. I can walk, although it isn't a great deal of fun. And fortunately, I still had a pass for the shuttle bus which had rides left on it, so I didn't have to try to walk across the Loop in the rain.
Overall, this is not a good way to start the day. I expect it will get better.