High-emission or yellow-labeled vehicles will be banned from Beijing roads from July to September to ensure green Olympics and Paralympics as promised by the authorities, environment officials said on Tuesday.

Vehicles on the Northern Third Ring Road at 5 pm in Beijing yesterday, the first day authorities ordered half the number of government cars off the capital's roads to ease congestion in the run-up to the Olympics in August. [China Daily]

There are currently more than 3.3 million vehicles in the capital. Yellow labels are displayed on the windscreens of more than 300,000 vehicles that fall short of the Euro I emission standard, the lowest of the European emission standards.

"All yellow-labeled vehicles, most of which are freight trucks, will be banned from roads in Beijing from July 1 to Sept 20," said Du Shaozhong, deputy director of the Beijing municipal environmental protection bureau.

"Limiting high-emission vehicles is the top priority in dealing with pollution," Du said.

While a target of 246 blue-sky days was achieved last year, air pollutants remain a major problem for the city, Du said.

A large number of freight trucks, mostly yellow-labeled ones that run through Beijing at night, have contributed to this problem greatly, Du said.

"There are 20 percent more air pollutants in the evening than during the daytime," he said.

"The period around 9 pm is always the time when the density of pollutants in the air start to rise and remain high until about 4 am."

Yellow-labeled vehicles are only permitted to enter Beijing between 7 pm and 8 am.

As part of the green drive, 22 laser remote sensing cars will be patrolling Beijing to check the emissions of vehicles, said Feng Yuqiao, the head of the motor vehicle department of the municipal environmental protection bureau.

"These inspection cars will mainly operate near the Olympic venues and training centers for athletes," he said.

"They can determine the emission levels of a vehicle in about 0.7 seconds."

The ban on yellow-labeled vehicles is the latest in a slew of measures to help clean up the capital's air.

Similarly, the authorities on Monday ordered half its government cars off Beijing roads till July 19.

The Ministry of Public Security announced on Monday that large trucks will be banned from certain traffic routes in the capital.

From July 1 to Sept 20, trucks entering Beijing will have to detour on national highway 112, which circles the city.

Some trucks, such as those carrying farm produce like vegetables and live pigs, will be exempt from the ban, but even these will have to apply for certificates from the municipal government to facilitate their movement in Beijing.

The capital also has plans for its 3.3 million private car owners to abide by an odd-and-even license plate rule that allows them to drive into the city only on alternate days, between July 20 and Sept 20.

The city already banned in March this year the sale of new cars that fail to meet new emission standards equivalent to Euro IV, currently the highest emission standard for cars.