This is not strictly on point but illustrates the importance of knowing the terrain where you operate a tractor or a mower, especially on a slope, especially where there are or might be holes or depressions on the downhill side or bumps, etc., on the uphill side. A man we knew was mowing around his pond with a zero-turn mower--the commercial kind that has two levers, one operating each hydraulic-drive system for each wheel, that you push or pull to cause the wheel on that side to go forward or reverse. Muskrats had undermined the edge of the pond. The ground gave way on the side of the mower near the water, the mower and this man went into the water, and his belt got caught on the handle of one of the levers. The result was the he could not get free of the mower, even though it had a ROPS, and he drowned. I have been mowing around our pond with a zero-turn mower, but I try to make absolutely sure I know where the muskrats have caused damage, and where in doubt I avoid the suspect area. And we just decided to plant weeping willows on the dam and stop mowing within six feet or so of the water there.