For clarity, “on infrastructure intended for small vehicles to do 20-40kph”. I mostly mean bike gutters on roads and dedicated bike paths as opposed to footpath/sidewalk with pedestrians.

I’d even allow kids as young as 14, they’re potentially great mobility enablers… But standards need to be met and they need to prove they’ll follow them. Licencing may be key, and potentially worth teaching through school.

I’d settle for a moped classification with cheap registration and basic licencing for kids that teaches them, “only use the throttle in bike lanes, and we’ll take the bike away if we see you do it anywhere else.”