Congestion charging to cut traffic and pollution has come into effect in the Swedish capital, Stockholm.
Drivers pay each time they enter or exit the city under the scheme
For a seven-month trial period, drivers entering or exiting the city during the daytime will be charged between 10 ($1.30) and 20 kronor each time.
A recent opinion poll suggested two out of three Stockholmers oppose the charge, but campaigners say the growing weight of traffic makes it inevitable.
Stockholm follows London, Oslo and Singapore in introducing the tax.
The toll will remain in place until 31 July. City residents will then decide in a 17 September referendum whether to keep the charge.
Traffic appeared to be running smoothly on Tuesday, the first day of the scheme, with the city government saying traffic was down 16% on Monday.
But officials warned the real test would come next Monday, when most Swedes return to work and school after the Christmas and New Year break.
One of the most forceful backers of the scheme is the Green Party, which insisted on its introduction in exchange for supporting the minority Social Democrat government.
One of its most vehement critics is the Swedish Automobile Association, which has called it a "violent attack on democracy".
Other critics say it is too expensive and that low-income commuters from the suburbs will be hardest hit.
"I hate these charges," resident Ingrid Ohman told Reuters news agency.
"They're pointless and a waste of money. It would be better to use the money to help people fix their teeth."
But a taxi driver, Mahmoud Rahmaniar Kooshaki, defended the scheme when he spoke to the AFP news agency.
"I think it's a good thing, because there is more and more traffic every year."
Taxis, motorcycles, private cars run on environmentally friendly fuels, and cars with foreign or diplomatic license plates are exempt from the charge, which will come into effect on weekdays between 0630 and 1829.
Drivers will pay up to 20 kronor each time they enter or exit the city, depending on the time of day, with a maximum daily charge of 60 kronor.
The revenue is earmarked for investment in public transport.
Extra buses and subway trains have been put in service to cope with the expected additional demand.
The aim is to reduce traffic by 10% to 15% in the city, which stretches across 14 islands.
Despite having only 760,000 inhabitants, Stockholm regularly falls prey to large traffic jams - an estimated half a million cars are thought to take to the roads every day.
London introduced its own traffic charging scheme in February 2003.
Despite initial widespread opposition to the scheme, traffic levels have been cut by over 15% and the zone in which the charge applies will be significantly expanded to the west of the city next year.