Millions of privately-owned cars have been banned from roads in Madrid in an attempt to improve air quality in the Spanish capital.
According to the city government, applicable restrictions for Friday will be announced by midday on Thursday for the region of Madrid, which includes the capital and the surrounding neighborhoods.
Local government sources said the restriction could alternate between odd and even number plates for as long as high levels of contamination persist.
The restrictions will be in place between 6:30 and 21:00 across the region. Drivers caught flouting the regulation will face fines of up to 90 euros.
The region has almost four million cars, plus about a million trucks, vans and motorcycles.
On Wednesday, the capital city also placed a temporary ban on parking in the center by non-resident car owners. It also restricted speed limits on Madrid's main circular road to reduce exhaust emissions.
The move follows a dry, sunny stretch of weather, which sent levels of nitrogen oxide, soaring above limits set by the European Union. Nitrogen oxide is a poisonous gas that can cause respiratory problems such as asthma.
Commenting on the growing pollution, Paz Valiente, an official in the city council, said, "Every day, the city pumps out a great deal of emissions in to the atmosphere, but it blows away... the current thermal pressure is impeding that ventilation."
The Spanish capital has been later than other major European cities in applying anti-pollution measures.
Paris, the French capital, has taken steps to pedestrianize some of its central roads while the British capital city, London, introduced a congestion charge more than 10 years ago.
The European Environment Agency (EEA) said in November that air pollution remains the single largest environmental health hazard in Europe, resulting in about half a million premature deaths per year.
The report had been based on data from official monitoring stations in more than 400 European cities. It said emissions of nitrogen oxides, which are linked to respiratory and cardiovascular diseases, from road transport had not fallen "sufficiently."
