They seem to catch on after the first couple of moves. That said, I have ran a few over, especially when I used the Salatin style tractors and couldn't see the birds. I really like the hoop house type.
This pic is from last year. When I replaced the tarp this year, I used a smaller one that doesn't go all the way to the ground. I like it much better, as it allows the wind to blow through it which keeps the birds cooler.
bigredfeather how many sq ft do you allow for each turkey in your hoop tractor?