|Critics wanted better roads and more education before the lane switch [EPA]
Samoa has made the switch to left-hand driving with hundreds of people lining the streets in the capital, Apia, to witness the change from driving on the right.
With car horns and sirens blaring, church bells ringing and roads crowded with vehicles, Tuilaepa Sailele Malielegaoi, the prime minister, broadcast the formal instructions for drivers to switch sides on the highways at 6am local time on Tuesday (17:00GMT Monday).
Police manned scores of checkpoints and warned drivers to slow down.
There were also no signs of immediate traffic problems despite critics' prediction of traffic chaos earlier.
The Samoan government declared a two-day national holiday to reduce traffic volume and a three-day ban on alcohol sales to avoid road accidents.
The switch aims to encourage some 170,000 expatriate Samoans in Australia and New Zealand to ship used cars with right-hand steering wheels back home to relatives.
This will make it cheaper for people in the nation of 180,000 to buy new and used cars built for driving on the left side.
The move was met by fierce opposition with critics asking for a postponement saying that people were not prepared for the change and road improvements have not been made.
Lefau Waikaimoana So'onalolole, the president of the People Against Switching Sides (Pass) movement, said "the efforts to prepare for the road switch are nowhere near completed", adding that necessary roadworks had not been finished.
"Not only that, but I believe there is much work to be done in educating everybody about the switch."
Experts had predicted the changeover would lead to more accidents on roughly surfaced roads, which are often fringed by high vegetation.
In church on Sunday, thousands in the largely devout Christian nation prayed for a changeover "free of injury and, heaven forbid, death", an editorial in the Samoa Observer newspaper said.
Bus companies had threatened to go on strike because the government refused to pay the cost of changing the exit doors to the opposite side of their vehicles.
However, most resistance has dropped off since a court late last month overthrew a legal challenge to the switch and the country has largely supported the bid to ensure a smooth changeover.
The speed limit was reduced from 56 kph to 40 kph, while speed bumps were installed in many busy areas.
Samoa, which has around 20,000 vehicles on its roads, is the first country to make the switch in nearly 40 years.
Iceland and Sweden did it in the 1960s, and Nigeria, Ghana and Yemen did it in the 1970s.
Source: Al Jazeera and agencies