Stockholm, Sweden ? Hundreds of European cities and towns restricted auto traffic Wednesday, part of the continent’s annual campaign to lower air pollution by encouraging commuters to use public transportation, bicycles or their feet instead of their cars.

More than 1,500 municipalities, chiefly in Europe, participated in the seventh annual car-free day campaign by setting up roadblocks to prevent nonessential automobile traffic from entering city centers. The campaign also spread to cities in Japan and South America.

“Listen how quiet it is here in the middle of the city,” said Winnie Berndtson, mayor for environmental affairs in the Danish capital, Copenhagen. “We had 1,700 children playing and learning about traffic today in streets that are normally packed with cars.”

In Stockholm, a busy thoroughfare in the southern part of the capital was closed to all vehicle traffic. People were encouraged to walk or ride bikes to browse shops, and a local group offered historical walking tours.

The Austrian capital, Vienna, closed segments of the expansive boulevard encircling downtown for four hours, giving pedestrians and cyclists a chance to take over the Ring Street, normally clogged by cars, trucks, buses, trams and horse-drawn carriages.

“The European Car Free Day initiative should be a motivator to reshape Austria’s traffic policy,” said Gabriella Moser, the Green Party’s spokeswoman for traffic issues.

But the closure irked the Austrian Federal Economic Chamber, which complained of delays in business deliveries and traffic in surrounding streets.

“The Environmental Ministry should be more interested in keeping traffic flowing than in causing increased noise and pollution by creating artificial traffic jams,” said Heinz Havelka of the group’s department for vehicle trade.

In the Finnish capital, Helsinki, where commuters make about 700,000 journeys daily on public transportation, customers were offered all-day tickets good on buses, trams, commuter trains and subways for $1.20. They normally cost $6.50.

Bicycles are the only mode of transportation for people going to work in central Copenhagen, Denmark. The city was one of hundreds participating Wednesday in Car Free Day.

“What we are trying to do is make people aware of the alternatives,” Environment Ministry official Leena Silfverberg said. “Maybe they will get a spark from the campaign and realize they could go to work in a more environment-friendly way.”

Some European cities, however, kept streets open. In most Italian cities, including Rome, traffic was as bad as usual, and residents remained unaware of the environmental campaign.

In Athens, Greece, the government decided not to ban cars because of the Paralympic Games. The government, which has banned cars in previous years, said residents should decide how to travel, but it made public transportation free.

Latvia has seen traffic in its capital, Riga, rise rapidly since the country regained independence from the Soviet Union in 1991. It will hold its car-free day Sunday, and is considering imposing a toll on drivers entering the city, similar to one imposed in London.