In Canada, the federal capital Ottawa; Montreal; Toronto and Hamilton in Ontario; and Victoria, British Columbia, were giving it a go. Canada, with a car for every two people, has one of the highest car-to-population ratios in the world.

Traffic in downtown Montreal was noticeably lighter, said a spokesman for the event, Simon Falardeau.

Though some businesses had protested the possible impact on their bottom line in weeks past there was no sign of strains over the event Monday.

"Car-free days" were first introduced in France in 1998 to enhance awareness of pollution from motor vehicles. The event is also an opportunity for real-life tests of some alternatives as traffic is barred to entire urban areas.

This year, more than 1,300 cities and towns in 36 countries took part.

TERRA.WIRE