Where are the primary commercial vehicle blind spots (puntos ciegos / zonas no visibles) located around a heavy truck or interurban bus?

1. Only directly above the roof
2. Four large zones: directly in front of the cab (under the windshield line), directly behind the trailer (for up to 60 meters), and along both sides, with the right-side blind spot being substantially larger than the left
3. Heavy commercial vehicles have zero blind spots due to large mirrors
4. Only beneath the fuel tanks