When can honking your horn result in a fine?

Following drivers being fined in Lisbon for honking in support of protesters, the Automobile Club of Portugal (ACP) clarified that the Highway Code restricts horn use to cases of imminent danger or, outside urban areas, to warn of an overtaking manoeuvre or poor visibility. Using the horn to protest or express discontent is not a valid reason and carries fines ranging from 60 to 300 euros, depending on the circumstances. Additionally, article 23 stipulates that light signals should be used instead of sound signals at night within urban areas.