Under what circumstance must hazard warning flashers (luzes de perigo / quatro piscas) be activated while driving on an Angolan highway?

1. When the vehicle is forced to decelerate abruptly due to a sudden traffic jam or breakdown hazard ahead
2. Whenever driving through a heavy rain shower at normal speed
3. To signal to following drivers that they are permitted to overtake
4. When double-parking illegally on a busy street