Communist Vietnam has banned police from wearing black sunglasses, chatting, smoking and putting their hands in their pockets while they are on duty in public places, a media report said.
Under a new order from the Ministry of Public Security, officers must also "keep appropriate manners and be in the right position when on duty," said the English-language website of state-controlled Tuoi Tre newspaper.
"This means traffic cops must not hide behind trees to ambush" and issue fines.
The report, published on Saturday, also said on-duty police were now banned from reading books, making or answering non-work related phone calls, drinking alcohol or eating at restaurants that illegally encroach onto pavements.
Vietnam's traffic police are seen by citizens as notoriously corrupt.
Last year US-based Human Rights Watch urged Vietnam to investigate "widespread police brutality", saying it had documented 19 incidents of reported brutality by law enforcers over the previous year, resulting in 15 deaths.