When I’m riding in our covered arena by myself I always leave the gate open. It’s some distance from the ring to the barn, and a rider in the ring can’t be clearly seen. I figure if I somehow hit the sand and get hurt, my horse will go back to the barn and tell someone. I know of a couple instances where unconscious riders were tended to quickly because their horses returned to the barn alone.
Of course, the only time I made a sand angel while riding my mare (we’ve been together for more than a decade), she just stood there aghast as I struggled back to my feet. I suspect she’d be more likely to take the opportunity to graze if left to her own devices rather than to sound a warning.
When there is a crowd in the ring, or with young horses, or with green riders, it’s usually safer with the gate closed. With well-trained horses, I see no problem leaving the gate back, especially if the area outside the gate is open and clear, although many people just shut it automatically. My mare clearly senses when I’m ready to head back to the barn and otherwise pays attention to her job, treating the area by the open gate no differently than along the kick rail.
Thus, I sometimes wonder why the rules for championship shows still insist on closing the gap at A, which is a huge drain on valuable volunteer time. As many tests as I’ve judged (more than 30,000), I don’t recall an older horse–First Level or above–making an unauthorized departure at A. It has sometimes happened, of course, with Training Level and Intro horses, and with green riders. Those are the ones who can really benefit from the gate being closed at A, but by the time a horse gets to a championship, even at Training Level, they pretty much understand that the little white fence is to be honored, even when it might have a gap.
I think the likelihood of a horse sliding out at A was worse when we used to have a lot of chain arenas, because the horses just didn’t respect them. The rings with solid rails make more sense to the horse, even if they’re low to the ground.
I did have an instance years ago of my Second Level horse sliding out the gate at A in a chain arena, but I was over-using my inside leg to prepare for a canter depart. My horse rightfully thought I wanted a leg-yield and obliged. I jumped right back over the chain and kept on going, since there was no whistle blast from the direction of C. The test sheet I got back mentioned something about a problem at A and a score of 5 for the depart–I won the class though. After I stopped laughing, I realized the judge probably couldn’t distinguish my horse’s white legs from the thin white chain from more than 200 feet away. Lesson learned: Don’t leg yield near A.