Car horns and sirens sounded, church bells rang out and roads were crowded with vehicles and smiling drivers Monday as Samoa marked its official switch to left-side driving.

Hundreds lined streets in the capital, Apia, to witness the switch from the right to the left on the country's highways as police manned scores of checkpoints, warning drivers to slow down.

The government is using the move to bring Samoa in line with Australia and New Zealand to encourage some of the 170,000 expatriate Samoans there to ship used cars „ with steering wheels on the right side „ home to relatives.

Despite opponents' predictions of chaos, there were no immediate signs of driving difficulties. Critics of the change had accused the government of pushing it through without adequately preparing drivers.

The switch from right to left side driving was being ushered in with a two-day national holiday to cut traffic volumes and a three-day ban on alcohol sales to avoid road crashes.

National Council of Churches chairman, Rev. Oka Fauoloto, held an early morning prayer service before Police Minister Toleafoa Faafisi used a national radio broadcast to instruct drivers everywhere to stop their vehicles.

Minutes later Prime Minister Tuilaepa Sailele Malielegaoi broadcast the formal instructions for drivers to switch sides on the highways at 6 a.m. local time (1700 GMT Monday).

Then drivers were ordered to resume their journeys. While there was some hesitation, traffic was soon flowing with guidance from police and local authorities as hundreds of onlookers lined streets to witness the historical day.

Prime Minister Tuilaepa Sailele Malielegaoi said the government has already widened roads, added new road markings and signs and installed traffic-slowing speed humps on key roads on the nation's two main islands of Upolu and Savai'i.

Despite much resistance and initially postponing the switch for more than a year, Tuilaepa said he's glad Samoa has finally done it.

"We thought it's unreasonable to postpone again so it's time for us to move," he said Monday.

Samoa is the first country in decades to switch the flow of traffic. Iceland and Sweden did it in the 1960s, and Nigeria, Ghana and Yemen did it in the 1970s.

The government will continue to allow vehicles with left-side steering wheels after the changeover, Tuilaepa said, and has still to address the problems of bus operators with both doors and steering now on the wrong side.

On Savai'i, the bigger of the nation's two main islands, the switch was disrupted by a protest in the village of Salelologa, where roadblocks stopped vehicles passing through the main street.

Officials said senior village members were in an early morning meeting with police.