↑Motor Power ∝ ↑Frequency of going at high speeds ∝ ↑% of time when a severe accident is possible.

I understand the argument that any given rider doesn't have to use the power. It's the same argument as "guns don't kill people, people kill people". While technically true, it ignores all of the evidence that shows that having the thing accessible increases its use in aggregate. I'm okay with people choosing to put themselves at risk, but a user of a more powerful eBike increases the danger for those around them as well. That kinetic energy works both ways when you hit someone else, and it's way easier to get up to that energy on a powerful eBike.

I hope we can agree that unlimited eBike power without a license is the incorrect policy. If my bike has as much power as a motorcycle (and electric motorcycles do exist), then I should need to be appropriately licensed. At some insane power, it should probably not be street legal. If you imagine a "smooth morph" between the most powerful electric motorcycle and the least powerful eBike on the market, there is some line where we need to transition categories. I'm willing to argue over where the various categorical lines around vehicle regulation and driver licensing should be, but I hope we can agree that they need to exist.

That said, I'm not sure that the ~25km/h limit in NY is the right limit, I might choose something more like 30-35km/h (~18.5-22 mph). But that's without any data and I'm not an expert, so 🤷

Its an odd way to convey that they meant the kinetic energy once you impact something. But power is Energy over Time, so they are talking about energy at that speed and its irrelevant if it is manmade watts or ebike watts

I should have clarified. I didn't mean motor power. These are power levels needed for any average bike to maintain this speed on level ground. You and your friend would definitely be hurt the same if you both went 45kph and fell the same way.

Speed is kinetic energy, and that’s the real worry when crashing: if that energy goes nowhere else, it goes into the fleshy human being.

100% and you can estimate how much kinetic energy is stored by looking at how much energy is needed to maintain that speed. Can use bike sim to get the numbers. And as you said - that's the energy that the meatbag would have to dissipate. The real interesting part which isn't obvious to everyone is that the energy grows exponentially with speed due to air drag. So falling at 40 hurts much more than 2x than falling at 20.