Why are motorcycle riders and moped operators classified as 'Vulnerable Road Users' (Usuarios Vulnerables de la Vía)?

1. Because their engines produce higher emissions
2. Because they lack a protective chassis/cabin, seatbelts, and crumple zones, meaning their bodies directly absorb impact kinetic energy during collisions
3. Because their vehicles are not required to carry license plates
4. Because they have right-of-way over all other vehicles at all times