How should an immobilised ADR vehicle be warned to other road users, using the prescribed equipment?

1. Place the two self-standing warning signs from the ADR kit and don the warning vest
2. Hang an orange plate on a tree 1 km away and leave the vehicle unattended
3. Use only the vehicle horn in short bursts
4. Rely solely on hazard lights, because warning signs are optional if the load is packaged