40mph is probably a bit extreme, but “20mph, tops” is also pretty low

E bike laws, terminology, and manufacturers can be kind of a wild patchwork of nonsensical bullshit but a lot of states recognize, with some degree of regulation or restrictions, what have commonly come to be called class 3 e bikes, that can go up to 28mph, and in my shopping around I’ve seen plenty that advertise that speed or even higher.

There’s a lot of imported e bikes that play fast and loose with the regulations and their quality control, and I’m sure there’s a dedicated bunch of people tinkering with their bikes to make them go faster and remove built-in restrictions, so there’s probably a lot of people zooming around at 30+MPH