Every time I see a RR rail cattle guard, I'm reminded of the fool who tried to walk a horse over one of these at one of the civil war re-enactments at Olustee, Florida in the early 80s. I still have no idea what he was thinking and when I came up on it, the horse's leg had gone down between the rails and the rider had the horse lying on it's side (the angle of which escapes my recollection today) and a couple of people were lying partially over the horse to keep him/her form getting up and snapping that leg.
I'm sure they got that horse out of there somehow as breaking it's leg would have made for news that would have gone through the event like lightning. But I always wondered how they did it.
-Lee
Flickr photo set of my On30 layout