I lack the commenting impulse control to say this in a politically correct way so my apologies for the outrage that will follow, but to put it crudely there is someone in my extended family who became a retard after falling off their bicycle at roughly walking speed and with a helmet on. It's rare but you can easily die just from walking and slipping on a banana peel.
While you're right about slower generally being safer, you should still treat it like a life-altering tragedy could happen at any time and like you're going 200 kph.
I'm sorry for your relative, and of course you should always do things like driving (diving, cycling, sailing, climbing - or even cooking and cleaning) as if a tiny mistake could cost you everything: that's because it's actually true. These activities will never be risk-free; the best you can do is bring the risk down to a level comparable to that of alternatives (with "just don't do it" included in the set) and hope no unfortunate incidents occur to you.
It's still worth noting the relative probability: death or life-changing injury is basically what happens in every single accident when you're going 200km/h on a highway surrounded by (what could as well be) steel walls moving at the same speed; in my use case, when not exceeding 40-50 km/h and using roads where other users basically stand still most of the time, you need a pretty specific conditions and a lot of bad luck to even have an accident, much less die or become permanently disabled as a result of one. Still, not a zero probability, but the difference between 100% and 0.01% is kind of noticeable.
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