Police have been given expanded powers to search people for weapons on every public bus, train and tram in the Adelaide metropolitan area ahead of New Year Eve's celebrations.

South Australia's Attorney-General Kyam Maher said all Adelaide Metro public transport services, stations, interchanges and Park 'n' Ride sites were now deemed Declared Public Transport Services or Declared Public Transport Hubs.

The announcement follows laws that were passed earlier this year which allow SA Police to search people for weapons in Declared Public Precincts and order a person posing a risk to public safety to leave the area for 24 hours.

"What this allows is once an area's declared a Declared Public Precinct, police has significantly more powers, in particular the ability to use handheld metal detector wands without having to have reasonable cause particularly to look for weapons like knives," Mr Maher said.

"This is about doing everything we can to make South Australia as safe as possible."

The expanded search powers apply to all public trams. (ABC News: Dean Faulkner)

Earlier this year, 11 shopping centres were declared public precincts while the Adelaide Oval and the Adelaide Railway Station were added to the list before the third Ashes Test earlier this month.

SA Police Assistant Commissioner Narelle Kameniar said since the powers came into effect, officers had conducted more than 4,000 searches and found 18 weapons.

"They've mostly been knives but there's also been knuckledusters and other items that have been seized," she said.

Police said a man allegedly carried a filleting knife on the first day the powers came into effect at the Adelaide Railway Station.

Assistant Commissioner Narelle Kameniar says all Adelaide public transport services are now Declared Public Precincts. (ABC News)

Assistant Commissioner Kameniar welcomed the expanded powers at public transport locations but said a review would be conducted after a 12-month period.

"People should be able to go about their lives and feel safe,"