What is the safest way to reverse a bus?

1. Reverse from the mirrors alone when a reversing camera gives a clear view of the area immediately behind the bus
2. Use hazard warning lights as a substitute for checking blind areas around the rear corners
3. Follow a guide's signals without separate all-round observation because the guide controls the manoeuvre
4. Avoid reversing where possible; otherwise move slowly, observe all around and use help if available