Sure, let me sneeze and cough on your lap bar, on the train before you get in.
That's a bit extreme, scottiemon, but yes--Germs can exist on any and every surface--including roller coaster trains. Assuming 2-across seating and 10-minute dispatches plus ride time, that's still about 10 people per hour to potentially get infected. And that's at one ride. You touch the train and then your face (you're going to do it, I guarantee it), congratulations! You just got Coronavirus! And those 10 people will infect more and more and more people.