China is planning to stage an annual car-free day across the country, an official with the Ministry of Construction said on Thursday.

Lan Rong, director of the ministry's department of urban construction, revealed the plan at the inaugural meeting of the China Urban Public Transport Association's intelligent traffic committee in Guiyang, capital of Guizhou Province.

"We will promote the event in order to encourage more citizens to choose public transport instead of private cars to reduce the worsening air pollution caused by car exhausts," Lan said.

Lan said China's Car-Free Day would be held annually in September in all the cities with a population of more than 500,000.

Each city would designate a certain area in which most vehicles will be banned for the day except shuttle buses, bicycles and emergency vehicles.

Lan said that with the acceleration of China's urbanization, public transport had become increasingly important.

But its development had lagged behind while the number of private cars on the road continued to soar, causing traffic problems in all major cities.

And pollution caused by the growing number of cars had affected residents' health and quality of life.

According to China's Clean Auto Movement Office, car exhausts have become the primary source of air pollution in many cities. In downtown Shanghai, car exhausts are responsible for 86 per cent of carbon monoxide in the air. In Beijing it is 80.3 per cent during summer and 63.4 per cent in winter.

Carbon monoxide inhibits the ability of blood to adsorb oxygen in the lungs. Inhaling high levels and concentrations can lead to poisoning.

"We hope more people recognize the benefits of taking public transport and the importance of our efforts to protect the environment by participating in Car-Free Day," said Lan.

China launched its first Car-Free Day in October 2000 in Chengdu, capital of Southwest China's Sichuan Province.