Start by getting in the habit of using hour PARKING BRAKE when you are PARKING.
It's not an "emergency brake". It's for PARKING, and if people would stop using that incorrect and STUPID term, "emergency brake", there would be a lot more people using their PARKING BRAKE and a lot fewer vehicles rolling away.
Not at all disagreeing with the good practice of using chocks when loading equipment, but it's always a good idea to start with Step 1.
I hope it’s understood by all….that the transmission “Park” lock 1- Only locks the rear wheels with a light-duty mechanism which is only intended for level terrain, and ….2- the “parking brake” only locks the Rear wheels from turning (and on most older vehicles with drums, only in the forward direction).
I hope it’s understood by all …that in the first video, the weight of the tractor depressed the rear of the trailer thereby lifting the tongue of the trailer…thereby lifting weight off the rear axle of the truck…thereby removing any effects of both Park and Park-brake from the truck, and that is why the combination rolled down-hill. The use of Chocks between the two axles on the trailer would have solved the problem….BUT, the guy Could Have simply continued forward upon the trailer and the tractor would have depressed the tongue back downward and stopped the entire action.
Pulling the breakaway prior to loading the tractor might have been beneficial in this instance….but that would also expose the electric-trailer-brakes to burn-out if too much time elapses. (The electro-magnet on the trailer-brakes’ armature cannot be relied upon except for a few minutes as it can overheat without the cooling effect of movement, and it can quickly drain a battery if not being concurrently re-charged. If the truck were not idling, it is unknown how long the man might have taken to retrieve the tractor for loading.) Chocks are the answer.
”Experience teaches us what we needed to know before the experience.”