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.
The existence of the handrail is proof of the potential for heavy inertia
Its existence is also kind of proof that emergency stops are slow enough that people can remain standing and squeezing a poll with 5 fingers will suffice for safety.