We used to have those walk behind tractors all over the country. Then those Japanese mini tractors started flooding the country and were just a better option for the operator for not much more money.
The biggest con of them is that those can't have a title and license plate, so those were worthless for most people that need to drive on the road.
The walk behind tractors, could and can go on the road with just insurance using a trailer with lights and beacon. These are custom built trailers with a diferencial and a 4 or 5 speed gearbox and seat on the tongue. The tractor powered this gearbox using the PTO. These little things would move a fully loaded trailer with logs up a steep hill like a mountain goat.
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Back in the day, my dad used to have one with a 18hp Lombardini diesel engine. Those engines were started by wrapping a rope on a pulley and pulling the rope. You either committed to pull that rope or it would rip your arm off. Well, one time my dad didn't quite committed to it, and the thing kicked back and started working backward. Loads of smoke everywhere but it still ran.