I had never seen one of these before today. They’re great. Way better than reaching for a single pole in a crowded car and wrapping your hand around some stranger’s fingers. And If you have the whole thing to yourself you can hook your arm through it.
Cool idea, but hooking your arm through it looks like a great way to break said arm if you stop fast.
Trains like this don’t decelerate that quickly when you pull the emergency break. If they did, you’d have injuries from standing, not being buckled, not having headrests, etc.