What are vehicles under official escort (vozila pod pratnjom) displaying flashing red and blue lights, and what priority do they possess?

1. They are specially escorted government/security convoys holding supreme priority over all other road traffic, including standard blue-light emergency vehicles
2. They are ordinary funeral processions that must obey all standard stop signs
3. They have priority only when travelling on motorways on weekends
4. Other vehicles may freely overtake them if space allows